# A64 Overclocking Guide



## cmberry20 (Jan 23, 2006)

Right, I’ve finally got round to starting my over-clocking guide for A64 CPUs as a lot of people are getting Opterons & want to overclock them. So let’s begin....

HTT - What is it?​Basically HTT is your memory controller's communication speed & stands for: HyperTransport Bus Frequency. The memory controller is integrated into A64 CPUS. The HTT is basically the FSB & some people will argue that calling it FSB is wrong so for this guide we will stick with calling it the HTT but will also refer to it as the FSB. A stock A64 processor has an HTT/FSB of 200, we need to increase this if we want to overclock.

CPU Multiplier.​Basically this value multiplies the CPU bus speed (HTT/FSB) by a set amount to get the final CPU speed. e.g. 200x*10*= 2000 (2Ghz) or an Athlon A64 3200. Really, all Venice core CPUs are identical, regardless of their price & speed. The only difference is their multiplier. The problem is that apart from the FX-** series all A64 CPUs have their multipliers locked at there highest (default) value, they cannot be increased, so you can’t buy an Athlon 3000 & turn it into a 3200 by increasing the multiplier. However all A64 CPUs can have their multiplier lowered.
A lot of people like to lower their multiplier to get a better HTT. This does work & a system that is set at 8x250=2000 will be slightly faster than a system at 10x200=2000. However, don’t use a fraction multiplier (eg. 9.5) the memory controller doesn’t like it & it may cause issues.
For the purpose of this guide we will leave the multiplier at its default level.

LTD/HTT​LDT (Lightning Data Transport) is kind of like the CPU multiplier but it multiplies the HTT to get the final Hypertransport frequency. The LDT is the HTT Multiplier & for Socket 939 motherboards the default value is x5. This gives you an overall HTT frequency of 1000 (200 x 5 = 1000) with socket 745 motherboards the LTD is x4 which gives it a overall frequency of 800.
So if we were to overclock our CPU HTT to 250 FSB the hypertransport frequency would be at 1250. This is much too high & will probably result in an unstable system. So we drop the LDT multiplier down to x4 to bring down the frequency to 1000 again (250 x 4 = 1000).
So 1000 (for socket 939 motherboards) is what we are trying to aim for. But if you were to use an HTT of 275 the frequency would be either 1100 (x4) or 825 (x3). Which one do we go for as neither are near 1000? Well it’s been proven that over-clocking the hypertransport frequency bus doesn’t increase performance & only makes a system unstable. And under-clocking the bus does not loose you performance, running it at 400 instead of 1000 only leads to about 0.1% drop in performance.
So always go lower than 1000 rather than higher.

Memory.​Your memory speed/frequency is tied in with the CPU HTT/FSB. At default settings your memory will run at a 1:1 ratio of your CPU speed. What’s this mean? Well if your CPU is set at 200 HTT (default) then your memory is also at 200 (DDR400) or 200:200 (1:1). If we increase the HTT/FSB of the CPU to 220 then the memory also increases to 220 (DDR440). This is where a lot of people start to hit problems. Standard cheap memory doesn’t like to be over-clocked, & soon the system becomes unstable when we are trying to overclock the CPU. Most people believe the CPU is unstable but in fact it could well be the memory being pushed too high.
So how can we overclock the CPU & not the memory? Well we need to use a thing in the bios called ‘Dividers’ a divider does essentially that, it divides the memory frequency by a set value to a ratio of the CPU HTT/FSB.
For example: If we have a CPU that can easily do 240 FSB but the memory is just plain DDR400 & wont overclock much we need to use a 5/6 divider, this gives a memory frequency of 200; back to DDR400 while the CPU is at 240.
Confused? Well it works like this: We take 240 (FSB) & divide by 6 this gives 40 (240/6=40) then we multiply it by 5 to get 200 (40x5=200).
Most motherboards have a selection of dividers; some show fractions others show RAM speed.
E.g.
200 = 1:1 (memory & CPU speed are the same)
166 = 5:6 (memory runs at 166 if CPU is set at 200, memory speed increases as CPU FSB increases)
150 = 3:4 (memory runs at 150 if CPU is set at 200)
133 = 2:3 (memory runs at 133 if CPU is set at 200)
100 = 1:2 (memory runs at 100 if CPU is set at 200)

One thing to do to get a better overclock is to run the memory at 1:1 with the CPU; however you need to get good memory to do this. If you want to keep the memory you have but over clock it you can always use looser memory timings or ‘Latencies’
Memory timings can be broken in to 4 categories and you some times to a set of 4 numbers that look like this: 2.5 / 3 / 3 / 6. Each number is a specific timing which can be altered to improve speed or stability. The timings are as follows:

CAS Latency Control (tCL) *2.5* / 3 / 3 / 6
This lantency is the delay in clock cycles between the assertion of the CAS signal and the availability of the data from the target memory cell. The timing usually comes in three speeds: 2, 2.5 & 3 where 2 is the fastest & found in expensive memory & 3 is the slowest & is found in cheaper memory. The lower the timing the better the performance.

RAS# to CAS# Delay (tRCD) 2.5 / *3* / 3 / 6
This number reflects the appropriate delay for your memory module between the RAS and CAS signals. Normally this value is between 2 & 4. Where 2 is used with expensive memory & 4 in cheaper memory.

Row Precharge Timing(tRP)  2.5 / 3 / *3* / 6.
This timing specifies the minimum amount of time between successive activate commands to the same DDR device. The shorter the delay, the faster the next bank can be activated for read or write operations. Again, the smaller the number the better the performance. Normally this value can range from 2 to 4. Where 2 is used with expensive memory & 4 in cheaper memory.

Min RAS# Active Timing(tRAS) 2.5 / 3 / 3 / *6*
This latency is the time when a row is activated until the time the same row can be deactivated. If the tRAS period is too long, it can reduce performance by unnecessarily delaying the deactivation of active rows. Normally this value is 6 or 7 where lower is better. Good memory tends to use 5 or 6 & cheaper memory 7 or 8


Command Per Clock(CPC)
This can also be known as ‘Command Rate’ & comes in two values 1T & 2T
This timing feature allows you to select the delay between the assertion of the Chip Select signal till the time the memory controller starts sending commands to the memory bank. The lower the value, the sooner the memory controller can send commands out to the activated memory bank.
Using 1T (or CPC enabled on DFI boards) will yield a much better performance than 2T. However, 2T is much more stable than 1T & when over clocking so it may be prudent to use 2T for the best result. A problem that a lot of people get is that when using a memory divider the memory controller is slightly strained & using 1T becomes difficult so using 2T becomes necessary.  But as a rule of thumb if you can run at 1T use 1T as it’s a lot better.

Ok, that’s the memory timings overview done with, as mentioned you normally find memory that has lower timings is better & more expensive, but this is not strictly true – let me explain….

If you want normal speed DDR400 memory & see one set at 2/2/2/5 timings you will normally find that this is a lot more than DDR400 memory running at 3/4/4/8. Also the lower timing modules usually enable you to overclock the memory by quite a lot. Memory that does 2/2/2/5 at 200Mhz (DDR400 ) might probably do 2.5/3/3/7 at 250Mhz (DDR500) .The cheaper higher latency DDR400 will only let you overclock it by a little. However, some expensive memory has slow latencies ( 3/4/4/8 ) but have very high clock speeds, maybe 250Mhz (DDR500 ) to 300Mhz (DDR600 ). The slower latencies enable the memory to run incredibly fast thus making it possible to run at 1:1 next to the CPU HTT/FSB speed.
So which one do you get, low (good) latencies but slower memory (DDR400 @ 2/2/2/5) or fast memory at slow latencies (DDR500 @ 2.5/3/3/7)? Well really in an ideal world you want low latencies & fast memory but this isn’t really possible or very expensive. A lot of people argue that memory speed isn’t really that important & latencies are what to go for. But in all benchmark tests that I’ve seen, memory running at DDR500 (250Mhz) & 2.5/3/3/6 wins every time over DDR400 (200Mhz) at 2/2/2/5. So I would go for high clock speeds.

If you are unsure why your PC is locking up or crashing then burn Memtest86+ on to a CD & run if for about 1 hour. If it reports any errors then your memory is not stable & you should think about changing your latencies, voltage or speed. 

Voltages.​
When over clocking your CPU there are three voltages to take into consideration, these are:
CPU Voltage.
RAM Voltage.
Chipset voltage.

CPU Voltage​The most important of the three is the CPU voltage. To get the best overclock it is more than likely you need to raise the CPU voltage. The default CPU voltage for an A64 CPU is 1.40v (for newer CPUs) however check what your CPU is to find out what vcore your CPU should run at.
There are certain rules to follow when adjusting the CPU voltage. Firstly, never increase the voltage by too much. How much is too much? Well most people say that for Venice/San Diego core CPUs the most you should go is 1.6v on air, or 1.65v with good air cooling. Just because your CPU is running quite cool with 1.65v doesn’t mean that 1.7v will be safe, it will probably lead to the CPU failing prematurely or it failing completely. If you are using water cooling then 1.7v up to 1.75v can be used.
The problem with increasing the CPU voltage is it increases the amount of heat that the CPU produces. So you may end up in a ‘Catch 22’ situation, where you need to increase the CPU voltage to improve stability but by doing so makes your CPU overheat & thus cause instability. There’s a very fine line that you need to go down to get what’s right for your system.

Max Voltages for certain CPUs (on Air)
Venice/San Diego/X2/Wincester = 1.65v
Newcastle/Clawhammer = 1.75v
Maximum ‘safe’ temp = 55C (under full load)

RAM Voltage​If you are increasing your RAM speed then you may need to adjust your RAM voltages.
Normal DDR RAM has a voltage of 2.5v or 2.6v but it depends highly on your type of memory. If you overclock your memory & are experiencing instability then increasing the DDR voltage may help. Try one step at a time, eg. 2.5v to 2.6v. Going too high may be unnecessary & cause the RAM module to overheat.
If you have generic RAM then 2.7v should be the maximum voltage. If you are using more expensive RAM with heatsinks then 2.8v should be ok. Some modules can go higher but check online with the manufacture to make sure.

Chipset Voltage​This is the voltage that is supplied to the motherboard chipset. If you are overclocking your CPU then increasing this a little may help with stability. But this should be the last voltage to change as its less critical the CPU & RAM voltages. Standard A64 motherboards have a chipset voltage of 1.5v. You should only need to up the voltage as high as 1.7v. For those running with a passive heatsink, check it by touching the heatsink to see if it’s running too hot if you increased the voltage. If it’s almost too hot to touch then you should think about lowering the voltage back down.


Overclocking your CPU​
Ok, now we get to the good bit – Overclocking!!!
When overclocking the CPU we want to eliminate other factors that may cause instability.

Firstly, manually set the CPU multiplier to the default value for your processor. Eg. Venice A64 3200 = 10. Don’t leave it on ‘Auto’ as some BIOS’s have a tendency to lower the multiplier if the HTT/FSB is increased.

Next, Manually set the LTD multiplier to ‘3x’ instead of ‘Auto’ or ‘5x’. Don’t worry about the finally value being less then 1000 as there is still enough bandwidth available to transfer data between PC components without bottlenecking problems.

Next, use a RAM divider of 1:2 or 100Mhz (Default 200Mhz) to set the RAM at half the speed of the CPU HTT/FSB. By doing this elimates the RAM as a potential instability problem. Even if you manage to get your CPU to 300HTT the ram will be at a nice low speed of 150Mhz. 

Finally, Increasing your Vcore. Now this is extremely difficult to just give a value & be done with it as everyone’s PC is different. Firstly some people have good cooling so they could use a larger voltage; others have different CPUs that can have slightly more voltage.
So, to be safe I’m going to be conservative with the values as I don’t want to wreck anyone’s PC.
If you have a Venice, Winchester, X2 or San Diego core (90nm) set your voltage to 1.50v to 1.55v. If you have an old A64 CPU with Newcastle or Clawhammer cores you can set the voltage a little higher: 1.6v to 1.65v. However, when setting voltages its always good practice to check your CPU temps. Never go above 60C underload as this is too hot. Its good practice to aim lower the 55C.

Once set have all the above parameters set its time to increase the HTT/FSB.
Start in steps of 10Mhz (15Mhz if you have the newer Socket 939 Opterons), so your HTT/FSB should be at 210Mhz. Boot into Windows run ‘Prime95’. Select ‘torture test’ under ‘options’ & ‘In Place Large FFTs’ Set Prime going & leave it for at least 15 minutes. Remember – Check your CPU temperature; make sure it’s not going past the ‘safe zone’ of 55C.
If no errors are found, reboot & increase the HTT/FBS by another 10Mhz.
Keep this up until Prime95 fails or Windows crashes. Go back into the bios & reduce the HTT/FSB by 3Mhz & test again, repeat until the PC is stable. It may be worth while to test with Prime95 for a minimum of 2 hours just to see if the PC is ‘fully’ stable at this point. Best run it over night to be sure. (Remember to always keep an eye on the temperatures)
When you have hit a wall & you cannot raise the HTT/FSB any higher, you can try increasing the Vcore slightly. Remember, don’t go higher than the values given earlier & always check your CPU temperature. When you get to the stage where you can’t raise the Vcore, FSB any more or your temperatures are too high then you have reached your CPU upper limit, make a note of the settings & its time to test the RAM.

Overclocking your RAM​
As with your CPU we want to overclock the RAM but take away other factors that may cause instability.

Firstly, leave the LTD multiplier the same as for the CPU overclock, at x3.
Next manually set the CPU multiplier quite lower, say x6. This will underclock the CPU thus making it run cooler & make it less stressed.
Finally, you want to set the memory divider back to 1:1 or 200Mhz (default).
It may be worth while to increase the memory voltage by one notch to improve stability when overclocking.

Ok, its time to overclock your ram.
Increase the HTT/FSB by 10Mhz, this also increases the RAM by 10Mhz, so if you are using DDR400 memory you now have DDR420 (210Mhz).
Test this by using MemTest86 for about 10 minutes to see if you get an error. (Use test No.5 for maximum burn in). If all seems ok, load Windows & try out 3DMark or a game & if all is stable increase your RAM again by 10Mhz.
Repeat this procedure until you get an error. When you do, lower the HTT/FSB by 3 or 4Mhz & test again. At this point you could try increase the RAM voltage a fraction more or adjust your RAM timings.
All RAM timings have different effects for different modules. Somebody with the same memory as yourself may get a better overclock with the same timings as you so don’t expect to get the same overclock as someone else.
Here’s a short list of timing starting from maximum performance & finishing with less performance but a better over clock.
2 / 2 / 2 / 5 (usually at 200Mhz)
2 / 3 / 2 / 5
2 / 3 / 3 / 6
2.5 / 3 / 3 / 7
3 / 4 / 4 / 8 (can get 250Mhz + with good RAM)
There are hundreds of other timings so mess about & see which one suits you.
Also try using 2T instead of 1T this may produce better results.

Once all parameters have been tried you should now have the maximum overclock for your RAM.

Now that we have the maximum overclock for both the CPU & RAM its time to combine both values. Reset the CPU multiplier back to its default value. Now adjust the memory divider to suit your overclock. Eg. Max CPU speed = 265, Max RAM speed = 230 so this requires a memory divider of 5:6 or 166. This only gives a memory speed of 220 but it’s not that much of a loss.

So, that more or less wraps it up. Have a go, make sure you don’t use too much voltage & always keep an eye on the temperatures.

Goodluck.



Useful Programs​
Below are some great utilities that help you test & check your PC when you overclock it.

*Stability Checking *

Prime95. Great little program that stresses your CPU to the limit. If your PC isn’t stable it generates an error. Used by overclockers to check if their system is stable.

Memtest 86. Checks your memory for errors. Completely independent from Windows & your CPU. Burn it onto a CD & boot from it. It will run automatically & check the motherboard memory for errors.

Sandra SiSoftware. Superb all round bench marking & stress test package. With this you can check system settings & it gives lists of all PC components. It can monitor system temperatures & benchmark the CPU & memory. Widely used by the overclocking community.

SuperPI. Nice little program that benchmarks your system. The quicker the time the better your PC is. Run 32M to check system stability, if your PC completes the task then its pretty stable.
A modified version of this program can be found here which adds fractions of a second to the timing. This version is mainly used by the overclocking community.


*Monitoring Utilities*

CPU-Z. Simple yet powerful program that displays CPU speeds, voltages, memory timings & other useful things.

Everest One of, if not, the best all round system information utilities on the market. This program can display system temperatures, voltages, fan speeds, hardware information & driver properties. It also has benchmark testing features. Unfortunately the freeware version was discontinued at the end of last year. However trial versions of the main programs are available.

SpeedFan. Can monitor system temps & voltages. Can also display real time temperature chart.  



To be added…….
‘UnderVolting’ guide.


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## trog100 (Jan 23, 2006)

nice guide.. pretty much answers all the oft ask questions..

trog


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## Migons (Jan 23, 2006)

Few more programs: 
StressPrime 2004 (Prime95 w/ better GUI)
Memtest86+


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## cmberry20 (Jan 23, 2006)

Memtest86 is already included.

Will look at including StressPrime


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## Jimmy 2004 (Jan 24, 2006)

Good guide - in response to memory timings, I found that with my RAM at the most agressive timings my mobo could take and a lower clock speed there was probably a marginal performance increase over higher clock and slower timings, just something to let others know. I've read this is because AMD64 CPUs have much shorter delays than many other processors (especially Intel) so this may not be true in other cases...


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## bim27142 (Jan 25, 2006)

my floppy disk just died.... is there a way i can make a bootable cd of memtest86???


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## cmberry20 (Jan 26, 2006)

yes. just download the iso image from the link found on the memtest main page. burn it onto a cd & boot from it.


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## Kryten (Jan 27, 2006)

cmberry20 great post..

thanks to this post i found out i was o/c my 64 completely wrong. I got it from 2.25 to 2.6 without locking up on me at all very informative.


as far as information programs i like aida32 its simple and tells you EVERYTHING about your computer. Sensor temps, fan speeds, Os install etc.. you name it. it even has a several benchmark tools in, plus its free  . simply unzip into a folder make a shortcut of the exe and opens right up.. older versions have a smaller splash screen than this one but meh..No spyware nothing but a basic info prog.  AIDA32


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## breakfromyou (Jan 27, 2006)

what about using systool! didnt' even mention it. horrible lol.

pretty decent...id add a few things about memory bandwith...my mem bandwith at 300dram 3-4-4-8 1T is pretty low, MUCH lower than it is at ~250@2.5-3-3-6. 2T kills bandwith, people say it performs as if the memory clock was 20 MHz lower...id avoid it completely, just use a divider.


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## W1zzard (Jan 27, 2006)

use can use the heading tag to make headings:

(heading)test(/heading) - use [] instead of ()

test​
same goes for subheading

[subheading]sub[/subheading]


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## cmberry20 (Jan 27, 2006)

Cheers W1zzard...... Much better. This was copied from another forum that i posted in which supported {size} in the text. I couldnt figure why this forum wasnt working so i left it.

Anyway...... AIDA32 was bought by Lavalys (Everest) which is featured in the links. Everest is very thorough.


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## cmberry20 (Jan 27, 2006)

breakfromyou said:
			
		

> what about using systool! didnt' even mention it. horrible lol.
> 
> pretty decent...id add a few things about memory bandwith...my mem bandwith at 300dram 3-4-4-8 1T is pretty low, MUCH lower than it is at ~250@2.5-3-3-6. 2T kills bandwith, people say it performs as if the memory clock was 20 MHz lower...id avoid it completely, just use a divider.



true. 2T does effect bandwidth but offers better stability. I cannot run 1T with my motherboard due to compatibility reasons but using my RAM at 265 Mhz @ 3/4/4/8 2T gives a better performance than 200 Mhz @ 2/2/2/5. I can get 29secs in SuperPi


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## breakfromyou (Jan 27, 2006)

cmberry20 said:
			
		

> true. 2T does effect bandwidth but offers better stability. I cannot run 1T with my motherboard due to compatibility reasons but using my RAM at 265 Mhz @ 3/4/4/8 2T gives a better performance than 200 Mhz @ 2/2/2/5. I can get 29secs in SuperPi



i was saying that theres a big difference between 1T and 2T at the same clock speeds, same timings.


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## zOaib (Jan 28, 2006)

i have a amd 64 4000+ clawhammer 

and have corsair xms pro pc3200c2pro and just pro (2 gig each) apparently i have seen people taking regular pro to 2-3-3-6 and the c2pro is alreayd rated at 2-3-3-6 , anyways just wanted to know is the clawhammer core multiplier locked at 12x , and how do i go about overclocking it , thx ?


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## breakfromyou (Jan 28, 2006)

zOaib said:
			
		

> i have a amd 64 4000+ clawhammer
> 
> and have corsair xms pro pc3200c2pro and just pro (2 gig each) apparently i have seen people taking regular pro to 2-3-3-6 and the c2pro is alreayd rated at 2-3-3-6 , anyways just wanted to know is the clawhammer core multiplier locked at 12x , and how do i go about overclocking it , thx ?



since you seem to have 4 memory modules, your system is forced to use a 2T command rate, and makes it a pain in the butt to overclock.

make sure your AGP/PCI/PCI-E clocks are locked to 66(agp)33(pci)100(pci-e). i think you can only do that with an nVidia chipset...if you dont have an nvidia chipset, and cant lock those buses at those clock speeds, i wouldn't recommend overclocking, as you could damage your graphics card and any other addon cards you have.

if you can lock your agp/pci/pci-e, raise your fsb by a few MHz at a time (~5, no more) and test it to see if it works and is at least half way stable by using prime95, or super pi even. try running either or even both for a few minutes. if it doesn't crash, or if there are no errors, then bump the front side bus up another 5 Mhz. do it until theres an error, then you have quite a few things that you could change. those being your processors voltage (vcore), your memory timings, your memory voltage (vdimm), and maybe even other things. i wouldn't do much unless you have an idea on what you're doing, since overclocking isn't very easy or exactly a quick thing to do, you could accidentally break something.

basically, read the first post :\


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## trog100 (Jan 28, 2006)

Abit via chipset boards lock the AGP/PCI/PCI-E buses just for the record.. they overclock quite well also.. he he












Abit AX8 VIA K8T890 chipset

amd 3700.. san diego core

nanya oem type cas.3 pc3200 ram.. 

trog


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## boruvka (Jan 28, 2006)

Oh - good to know. I'm quite torn apart which Socket 939 board to buy:

- should have all the OC goodies (lockable PCI bus / abundant RAM dividers = more than just DDR400,333,266,200! / VCore&VDimm settings up to x,8V / >2 fan connectors / by-MHz-settings of HTT)

- a plus (but no no-go) would be any or all of the following: true AGP Port / no fans on chipset / chipset no heating device (nF4 chipsets reportedly get red hot) / not exceeding 80 € pricetag)

Sadly, no one builds EXACTLY my board of dreams. I want a no-frills mainboard with very many OC options. The manufacturers seem to think that OC enthusiasts also need every other thing possible to be integrated onto a mainboard. I have no firewire devices. SATA usage is often prohibiting a higher overclock. I scarcely play 3D games and would prefer buying one strong performer of a GPU over two lesser lights (SLI/Crossfire). I need neither GbLAN nor WLAN or RAID.

The cheap and moddable Asrock Dual Satan II   has some of the features (PCI lock, full AGP, nice price, no fan) but not much in the way of RAM dividers (or has them the ocworkbench mod-BIOS?). 

If you say the K8T890 chipset also has a PCI-bus-lock, I would have more options. I get desperate waiting for the Abit UL8pro, are there asian TPU folks around who could tell me whether it's already for sale in asia? Would have to exchange my GPU for a PCIe version, though, in both cases (K8T890 as well as ULi1697). 
The K8T800pro doesn't have a PCI lock, right?


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## trog100 (Jan 28, 2006)

Arctic Cooling Rev.2 ATI 5 (X850 Series) VGA Silencer (HS-018-AR) --- £14.04

Zalman CNPS9500-LED Aero Flower (Socket 939/754/478/775) CPU Cooler (HS-015-ZA) -- £41.07

Coolermaster Neon LED 80mm Fan - Blue (FG-000-CM) --- £3.47

Abit AX8 VIA K8T890 (Socket 939) PCI-Express Motherboard (MB-063-AB) --- £70.44

AMD Athlon 64 3700+ San Diego 90nm (Socket 939) - Retail (ADA3700BNBOX) (CP-121-AM) --- £171.49

OcUK Value 2GB (2x1GB) PC3200 184pin DDR Memory Dual Channel Kit (MY-006-OK) -- £113.92

Sapphire ATI Radeon X800 GTO² 256MB DDR3 TV-Out/DVI (PCI-Express) - Retail (GX-101-SP)  £154.44

Jeantech Arctic JN120F-600AP12V2 power supply £65.99

total --- £634.46

#####

the pirces are a month old and might be little cheaper now.. 

my selection for a high-ish end budget system.. 

i got all my stuff from overclockers UK except the jeantech power supply that came from pcworld.. 

i would describe the ax8 as a perfect budget overclockers board..  it  has only one pci e slot thow no good for two grfx cards.. the other board u mention (K8T800pro) is agp only.. i think it has all the overclocking options thow..

i get 7000 in 3dmarkd2005 and the whole lot goes quite well.. the abit guru software fans and cpu control works like dream.. 

not total high end but bang for buck wise near unbeatable.. another four hundred quid grfx wise would make it really high end but somewhat dent the value for money factor.. he he

temps... no fan on chipset passive.. the case runs at 1.5c over room ambient and near silent at idle.. case fans controled by what would be the chipset fan controler..







trog

ps.. before any US dude does a  currency conversion and says that aint cheap.. UK wise it is.. we pay more period..


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## bim27142 (Jan 30, 2006)

cmberry20 said:
			
		

> yes. just download the iso image from the link found on the memtest main page. burn it onto a cd & boot from it.



tried it but how can i burn them? nero can't find the file (it says it's not supported)... is there something i'm missing?


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## breakfromyou (Jan 30, 2006)

its the image you have to burn...burn the image as a bootable cd


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## trog100 (Feb 7, 2006)

whoosh


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## largon (Feb 7, 2006)

cmberry20 said:
			
		

> Memory.​Your memory speed/frequency is tied in with the CPU HTT/FSB. At default settings your memory will run at a 1:1 ratio of your CPU speed. What’s this mean? Well if your CPU is set at 200 HTT (default) then your memory is also at 200 (DDR400) or 200:200 (1:1). If we increase the HTT/FSB of the CPU to 220 then the memory also increases to 220 (DDR440). This is where a lot of people start to hit problems. Standard cheap memory doesn’t like to be over-clocked, & soon the system becomes unstable when we are trying to overclock the CPU. Most people believe the CPU is unstable but in fact it could well be the memory being pushed too high.
> So how can we overclock the CPU & not the memory? Well we need to use a thing in the bios called ‘Dividers’ a divider does essentially that, it divides the memory frequency by a set value to a ratio of the CPU HTT/FSB.
> For example: If we have a CPU that can easily do 240 FSB but the memory is just plain DDR400 & wont overclock much we need to use a 5/6 divider, this gives a memory frequency of 200; back to DDR400 while the CPU is at 240.
> Confused? Well it works like this: We take 240 (FSB) & divide by 6 this gives 40 (240/6=40) then we multiply it by 5 to get 200 (40x5=200).
> ...


DRAM ratios work that way on AXP and Intel platforms but A64 is another animal...

*HTT itself has *nothing* to do with ram frequency on AMD K8-series.*
Memory frequency on K8 is derived _directly from cpu frequency._

*DRAM Clock* = *CPU Clock* / *Ceil(Memory Divider**)
Ceil(x) returns the smallest integer value ≥ to the original value.

*Memory dividers:
Divider "250" = CPU multiplier - 3
Divider "233" = CPU multiplier - 2
Divider "216" = CPU multiplier - 1
Divider "200" = CPU multiplier
Divider "183" = CPU multiplier + 1
Divider "166" = CPU multiplier + 2
Divider "150" = CPU multiplier + 3
Divider "140" = CPU multiplier + 4
etc.

Example 1: 
CPU multiplier = *9*
HTT = *250MHz*
CPU Clock = *2250MHz*
Divider "166" = CPU multiplier + 2 = 9 + 2 = *11*

*DRAM Clock* = *2250MHz* / *11*
= *204.5MHz*


Example 3: 
CPU multiplier = *9*
HTT = *235MHz*
CPU Clock = *2115MHz*
Divider "233" = CPU multiplier - 2 = 9 - 2 = *7*

*DRAM Clock* = *2115MHz* / *7*
= *302.1MHz*


Example 4: (a non-integer multiplier): 
CPU multiplier = *8.5*
HTT = *250MHz*
CPU Clock = *2125MHz*
Divider "166" = Ceil(CPU multiplier + 2) = Ceil(8.5 + 2) = *Ceil(10.5)* = *11*

*DRAM Clock* = *2125MHz* / *11*
= *193.2MHz*[/QUOTE]

[edited copypaste from my post @ OCF]


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## trog100 (Feb 8, 2006)

all sounds over complicated to me..

there is an external clock.. default = 200.. often refered to as the fsb..

this governs everything else by dividers or multiplyers.. 

default memory speed for ddr400 (200/400) would 1 x the external clock.. = 200 or 200/400.. memory speed runs the same as the external clock speed.. 

default memory speed for ddr333 (166/333) would 5/6 x the external clock..= 166 or 166/333 its actually a bit less but it dosnt matter.. memory speed runs at 5/6 the external clock speed.. 

default htt would be external clock 200 x 5 = 1000.. hht runs at 5 x external clock speed.. 

default cpu speed for example with an amd 64 3700 would be external clock.. 200 x 11 = 2.2 gig.. cpu runs at 11 x external clock speed.. 

pretty much everything is governed by the external clock.. if for example u up the external clock speed from its default 200 to say 250.. everything else would would go up accordingly.. 

200/400 memory would be trying to run at 450/500 speeds.. 

hht speeeds would be 250 x 5 = 1250.. 250 faster than it should be.. 

cpu speed would be 250 x 11 = 2.75 gig.. 550 faster than it should do..

200 to 250 for example is a 25% speed increase.. some things will stand this speed increase others wont which is why u have to play with muliplyers and dividers..

there is no front side bus as such with the 64 bit chip.. just an external clock..

trog


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## largon (Feb 8, 2006)

The thing is that in K8 architecture memory receives it's frequency from the memory controller not the source clock. 

Plus the fact that ratios don't explain all memory frequencys.


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## trog100 (Feb 8, 2006)

i dont fully understand it all.. and the memory controler on chip does seem to remove the need to drop your mulitplyer and increase the so called fsb clock.. simply increasing cpu speed seems to do pretty much the same as increasing cpu speed and increasing fsb speed did before..

clocking the amd 64 would be lot easier if the multiplyer wasnt locked upwards.. he he

trog

ps.. i wasnt trying to go against anything u said by the way.. just trying to explain the basics in very simple terms.. not always easy to do and sound plausible.. usually if its easily understood it cant be right and if its  complicated  it has to be right just never understood.. he he he


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## zOaib (Feb 8, 2006)

largon said:
			
		

> The thing is that in K8 architecture memory receives it's frequency from the memory controller not the source clock.
> 
> Plus the fact that ratios don't explain all memory frequencys.



largo can u put it in more simple words , or examples .............. like what would be a step or steps to take in series to go from a 2.4ghz to above , thx ,


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## breakfromyou (Feb 9, 2006)

so exactly what is the formula? to find out what your memory would run, say if you used a memory divider, with a 10.5 cpu multiplier?

half multipliers confuse me. dram clock usually jumps down a bit.


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## sinner33 (Feb 9, 2006)

The multiplier when it is 10.5, rounds the memory down to if the multiplier was 10. For memory, there is no such thing as half a multiplier. That is just something you can do on your motherboard =P Ex: 9.5=9,10.5=10, 11.5=11.


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## trog100 (Feb 9, 2006)

u would find your memory max by lowering the cpu multiplyer to slow it down then upping the external clock to speed your memory up.. this will also speed your cpu up but the memory should reach its max out point first..

example.. cpu multiplyer should be 11.. dropping it to 9 would lower the cpu speed by 2 x external clock.. the memory speed would still be at 1 x 1 external clock.. 200/400.. as u take up the external clock both memory and cpu go up with it.. but being as the cpu started off 400mhz less than its default it has plenty of room left to go up in speed.. your memory dosnt so it should bomb out first.. 

trog


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## zOaib (Feb 9, 2006)

trog100 said:
			
		

> u would find your memory max by lowering the cpu multiplyer to slow it down then upping the external clock to speed your memory up.. this will also speed your cpu up but the memory should reach its max out point first..
> 
> example.. cpu multiplyer should be 11.. dropping it to 9 would lower the cpu speed by 2 x external clock.. the memory speed would still be at 1 x 1 external clock.. 200/400.. as u take up the external clock both memory and cpu go up with it.. but being as the cpu started off 400mhz less than its default it has plenty of room left to go up in speed.. your memory dosnt so it should bomb out first..
> 
> trog



that makes sense !

so how do i raise my memory after putting down my cpu say 400mhz from a 2.4 to a 2.2 ?

WHAT do i do next to increase the mem , is it the timing u r talking about or the mhz ?


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## cmberry20 (Feb 9, 2006)

largon said:
			
		

> DRAM ratios work that way on AXP and Intel platforms but A64 is another animal...



No, they also work with A64s as well. Not all motherboards (BIOS's) are the same so the guide is just a guide & is meant as an example. I own a MSI Neo 2 Plat Skt939 AGP & the ram dividers work just like I quoted. If i set my RAM speed to 166 & the HTT is at 200 the memory works at a ratio of 6/5 to the CPU FSB/HTT so my RAM is running at 166Mhz. Therefore if i set my HTT to 250 i get a  a RAM frequency of 208Mhz.
I'm not saying you are wrong but i think your BIOS works differently to mine.



			
				largon said:
			
		

> *HTT itself has *nothing* to do with ram frequency on AMD K8-series.*
> Memory frequency on K8 is derived _directly from cpu frequency._


Again not true - see above. But your statement contradicts itself. How can the ram frequency NOT be connected to the HTT when the HTT governs the cpu frequency. If you raise the HTT you raise the cpu frequency thus raising the ram frequency - do you see!!


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## zOaib (Feb 9, 2006)

now i am definately confused !


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## cmberry20 (Feb 9, 2006)

i'm going to look at clearing the memory divider business up. It is a little confusing plus my motherboard (NForce3) may be different to common ones (NForce4)


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## zOaib (Feb 9, 2006)

cmberry20 said:
			
		

> i'm going to look at clearing the memory divider business up. It is a little confusing plus my motherboard (NForce3) may be different to common ones (NForce4)



if u can fidn a good standardised explanation for how to go about overclocking , that would help a lot of us low level brains here ! thx


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## largon (Feb 9, 2006)

*cmberry20*,






Ok. 208MHz with source clock 250MHz and divider "5/6" (166). 

What happens if we drop to 9x250?




Huh? Memory frequency dropped from 208MHz to 205MHz? 

Glitch? Well, let's try 8x250...




Now it went down to 200MHz?

What's going on? Why memory frequency is not 208MHz like it should be with divider 5/6? And WHY does the frequency decrease if multiplier is lowered?



This is why:



> DRAM ratios work that way on AXP and Intel platforms but A64 is another animal...
> 
> *HTT itself has *nothing* to do with ram frequency on AMD K8-series.*
> Memory frequency on K8 is derived _directly from cpu frequency._
> ...



->

Divider "166" = CPU multiplier + 2

1st pic:
10 * 250.52 = 2505.2
2505.2 /12 = 208.77 = *208.8*

2nd pic:
9 * 250.52 = 2254.68
2254.68 /11 = 204.97 = *205.0*

3rd pic:
8 * 250.52 = 2004.16
2004.16 /10 = 200.42 = *200.4*

*□*


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## trog100 (Feb 9, 2006)

i think different mobos call things by different names and have different ways of alterings things.. i cant do a screen shot of my bios screen.. else i would.. 

try wadeing thru this link.. he he

http://forum.overclockersonline.com...74&start=0&S=0bd708b11e5a7d833e52e0164ef89a4b


trog


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## cmberry20 (Feb 9, 2006)

Largon, I see what you've done about the HTT not being related to the memory frequency. While this is completely true in your example & I'm not disagreeing with this method but my guide was written with the fact that the CPU multiplier is remaining the same when overclocking thus the HTT & dividers would only be responable for the memory frequency altering.

I'm in no way trying to prove yourself or anybody wrong, feedback is always welcome & will be updating the guide & memory dividers information later this month. Thanks.


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## largon (Feb 9, 2006)

> I'm not disagreeing with this method but my guide was written with the fact that the CPU multiplier is remaining the same when overclocking thus the HTT & dividers would only be responable for the memory frequency altering.


Let's compare _ratio method_ and err... _*"*my*"* method_ but this time cpu multiplier stays the same:




8 * 237.7 = 1901.2
1901.2 / 11 = *172.8*
Ratio method: 
237.7 * (3/4) = *178.28 - wrong* 





8 * 275.5 = 2203.9
2203.9 / 11 = *200.4*
Ratio method: 
275.5 * (3/4) = *206.6 - wrong*





8 * 280.04 = 2240.04
2240.3 / 11 = *203.7*
Ratio method: 
280.04 * (3/4) = *210.0 - wrong*

Ratio method gives *wrong* frequency with every multiplier other than 10.


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## cmberry20 (Feb 10, 2006)

Thanks Largon, will be updating my guide to show correct memory divider calculation.


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