# Phenom II 940, M3A78-T FSB overclock problem



## Guyonskis (Jun 14, 2009)

I managed to get my Phenom II 940 to 3.6 Ghz stable just by changing the multiplier to 18x and raising the VCore to 1.5v. I then tried to raise my FSB to 206Mhz (for 3.7) and it failed prime95 blend test. Anything more and it would BSOD or just crash. I've tried raising memory/NB voltage to 1.2v/1.4v which didn't help. I tried lowering the multiplier to 17x and raising the FSB to 220, same thing. I also tried raising/lowering my NB multiplier, no difference. I limit the memory frequency and let the board choose my timings: FSBRAM 1:2 (seems low?), 5-5-5-15-23 currently. My temps are good CPU idle 28C, load 34C.
Any ideas on what is causing these problems when I raise the FSB?
Are BSOD/crash/prime95 failure caused by different things? 

I'm a semi-noob at overclocking so maybe I'm missing something... what do I need to consider when raising the FSB? 

Thanks in advance!


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## demonkevy666 (Jun 15, 2009)

it' not FSB it's HTT or hyper transport reference speed.
can you read the bsod before it go's ? 

I don't know what speed your ram is, but some times pushing it some ram hates it.

I get about 3.740ghz @ 1.475v but I'm running vista ultimate 64 bit.


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## cdawall (Jun 15, 2009)

demonkevy666 said:


> it' not FSB it's HHT or hyper transport reference speed.
> can you read the bsod before it go's ?
> 
> I don't know what speed your ram is, but some times pushing it some ram hates it.
> ...



its HTT no HHT 


sme 940's were dogs a oc'ing put the volts around 1.55v and NB volts around 1.4v


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## demonkevy666 (Jun 15, 2009)

cdawall said:


> its HTT no HHT
> 
> 
> sme 940's were dogs a oc'ing put the volts around 1.55v and NB volts around 1.4v



why aren't we using the R & S ??? lol 

it should be HTRS.


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## chuck216 (Jun 15, 2009)

Dumb question but if you want 3.7 Ghz why not just use a 18.5 multiplier and avoid all the mismatched HTT bus and ram speed problems? A little extra voltage on the v-core maybe up to 1.525 should get it stable on air.

You shouldn't need to raise the FSB with a Black Edition chip except to tweak the last little bit of overclock.

(and yes I know it's "HTT reference speed" now but I'm old school and I'll always call it FSB)


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## Guyonskis (Jun 15, 2009)

@ demonkevy666 - I think the BSOD was something to do with memory

My old CPU stopped working so I'm hesitant to raise the voltage to much. The spec for the 940 gives a range up to 1.5v so I would prefer to leave it at that. Is the only danger of voltage from heat or could it damage a processor in other ways?
Would the v-core requirement be the same for 18.5 x 200 as 18 x 206 or 17 x 218?


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## Exeodus (Jun 15, 2009)

Guyonskis said:


> @ demonkevy666 - I think the BSOD was something to do with memory
> 
> My old CPU stopped working so I'm hesitant to raise the voltage to much. The spec for the 940 gives a range up to 1.5v so I would prefer to leave it at that. Is the only danger of voltage from heat or could it damage a processor in other ways?
> Would the v-core requirement be the same for 18.5 x 200 as 18 x 206 or 17 x 218?



It has been my experience that ASUS boards don't overclock the bus very far past 200 on Phenom II class processors.  Most 940's seem to acheive max stability around 3.6ghz.  They will game and bench higher, but won't pass most stress tests.


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## crunchie (Jun 15, 2009)

Max safe vcore on the 940BE is actually 1.425 according to AMD.
Read it on the pdf here; http://www.amd.com/us-en/assets/con...d_tech_docs/GH_43375_10h_DT_PTDS_PUB_3.18.pdf
I always thought it was 1.55, but there you go.
Surprised you cannot go higher on your clock though. I can get 4.0GHz on 1.475vcore.
Set your vcore to something like 1.45-1.5 and then keep raising your multi until you have problems with stability. It's up to you then if you want to up the vcore, or accept that your chip does not want to go any higher.
3.6 cpu and 2.6 cpu/nb is a nice OC to settle on imo.


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## cdawall (Jun 15, 2009)

Exeodus said:


> It has been my experience that ASUS boards don't overclock the bus very far past 200 on Phenom II class processors.  Most 940's seem to acheive max stability around 3.6ghz.  They will game and bench higher, but won't pass most stress tests.



mine will do 300HTT tested by me on a 955BE


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## Guyonskis (Jun 15, 2009)

Exeodus said:


> It has been my experience that ASUS boards don't overclock the bus very far past 200 on Phenom II class processors.  Most 940's seem to acheive max stability around 3.6ghz.  They will game and bench higher, but won't pass most stress tests.



That's sad to hear! You're right, 3.7 was stable enough to game and run 3Dmark... just failed the stress test. 



crunchie said:


> Max safe vcore on the 940BE is actually 1.425 according to AMD.
> Read it on the pdf here; http://www.amd.com/us-en/assets/con...d_tech_docs/GH_43375_10h_DT_PTDS_PUB_3.18.pdf
> I always thought it was 1.55, but there you go.
> Surprised you cannot go higher on your clock though. I can get 4.0GHz on 1.475vcore.
> ...



They're big liars lol http://products.amd.com/en-us/Deskt...&f5=&f6=C2&f7=45nm+SOI&f8=&f9=&f10=False&f11=

I guess I shouldn't complain about 3.6 ... I'm just curious about how far my air cooling can get me. Haf 932 is awesome!


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## Guyonskis (Jun 15, 2009)

cdawall said:


> mine will do 300HTT tested by me on a 955BE



With what voltages? Did you change other multipliers, like NB? 

I think I may need to get me a M4...


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## cdawall (Jun 15, 2009)

Guyonskis said:


> With what voltages? Did you change other multipliers, like NB?
> 
> I think I may need to get me a M4...



multi was dropped and the NB was@10x HTT link@7x


HTT volts@1.33v, NB@1.45v, cpu@stock


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## Fatal (Jun 15, 2009)

Maybe post some screen shots of CPUz from looking at your rig you have 4x1GB sticks. That would be a problem depending on if they are overclock you have to drop the bandwidth to the next lowest clock. So if they are 1066>800 or 800>667 or 667>533 what are the sticks rated to run? This will allow others to help you better


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## Guyonskis (Jun 15, 2009)

PC6400 800Mhz... can it not go any higher? I believe I tried lowering it to no avail... but I think I changed something else as well that time. I can try only turning my memory down. Won't that affect my overall performance though?

I'll try to post pics later today.


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## crunchie (Jun 15, 2009)

Try 2 sticks only as well as the cpu is stressed more when all 4 dimms are populated.
If you find you are more stable at higher frequencies, go for some 2x2 sticks.


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## Guyonskis (Jun 16, 2009)

Fatal said:


> Maybe post some screen shots of CPUz from looking at your rig you have 4x1GB sticks. That would be a problem depending on if they are overclock you have to drop the bandwidth to the next lowest clock. So if they are 1066>800 or 800>667 or 667>533 what are the sticks rated to run? This will allow others to help you better
> 
> I tried dropping the RAM frequency and upped the vcore to 1.525v. I tried a bunch of combinations (17x218, 16x231, 15.5x238) and dropped the NB multiplier. Crashes/BSOD. My RAM never went over 800Mhz. I'll have to try with two sticks.


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## Fatal (Jun 16, 2009)

I can get my CPU to beach at 3.7 and 3.8 but far as 24/7 use 3.6 is as high as my CPU will allow. The memory you have did it come all together or is it two kits? That can be a problem if they are two kits. Using one of the sets will help see if the memory is in fact the issue.


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## Guyonskis (Jun 16, 2009)

Two kits.  
Well if it works well with two sticks I'll have an excuse to buy some fancy RAM!

Does the order I put them in matter with two kits? I think I put two in the first two slots, and two in the next two. Could this be causing problems?


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## crunchie (Jun 17, 2009)

If the dimms are colour coded, put one kit in one colour and the other in what's left 
Running 4 sticks _will_ stress the cpu more and bring down your OC.


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## Fatal (Jun 17, 2009)

“Mixing ram is not going to be recommended, it also reduces overall memory performance.” 

http://www.ocztechnologyforum.com/forum/showthread.php?t=46755&highlight=OCZ+platinum+PC6400+800Mhz 


http://www.ocztechnologyforum.com/forum/showthread.php?t=42686&highlight=OCZ+platinum+PC6400+800Mhz 

With you running two kits I would say your main goal should be to see if the kits can work as one stock settings first. So install all four and use the stock settings see if your system can run with all four sticks stock setting. Maybe run Memtest or OCCT with the sticks in as well to be sure that it is stable with the four sticks. If so then see how much you can overclock them. I did some looking for those sticks above links. My brother has been running a mixed pair of 1gig Corsairs for over a year and they are overclocked so it is possible. If not then your best bet would be to get a set of 2x2 gig sticks 

Memtest
http://www.memtest.org/ 

OCCT
http://www.ocbase.com/perestroika_en/index.php?Download 

DDR2 800 (PC2 6400)

http://www.newegg.com/Product/Produ...0147 1052416064 1052315794&name=4GB (2 x 2GB) 

DDR2 1066 (PC2 8500)

http://www.newegg.com/Product/Produ...4&bop=And&ActiveSearchResult=True&Order=PRICE 

The price is pretty close depending on what company you go with between 1066 and 800 memory. It can be difficult to run four but has been done good luck.


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## Guyonskis (Jun 17, 2009)

Thanks for all the help! Great links.

Ok so I tried 206 with only one kit, no improvement. 
I think perhaps something strange is going on with my voltage. I set vcore to 1.55 and pushed the multiplier to 18.5 and it seems stable so far (35c load). CPUz shows 1.55v but pc-probe is only showing 1.51v.  Maybe I'm not getting the voltage I ask for and that's limiting my OC. I'll test it later with 18x, 206 FSB. 
If the temps are good does it matter how high the voltage is? Can CPU damage occur at lower temps?

I think I may buy 2x2 corsair dominators pc8500 anyways... the fans will look awesome and I won't have to worry about memory anymore.

Edit: 18.5 is not stable, failed in less than 3 hours. Sigh.


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## Fatal (Jun 17, 2009)

As I stated I cant get anything higher than 3.6 in OCCT stress test. Sure I can run it at 3.7-3.8 and will be fine will not crash one bit. 1.55v seems a bit high I can get 3.7 with 1.48v and 3.8 with 1.48v-1.50v. The only issue is its not OCCT stable. Which program are you using to check to see if its stable? If you are getting 35c load your rig has some serious cooling . Which slots are you using the ram in? I think I read in those links I sent you that the black ones were better to use. 

I will have to research your board more so I can be more help for you. Maybe some one in the forums here has your board and will step in to assist as well.

Edit:
Is Cool n quiet and TLB Fix disabled just making sure cause they have to be.


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## Guyonskis (Jun 17, 2009)

So when I read about people claiming 3.8, it just means that they can boot windows? THAT has never been an issue... I haven't tested how far I can go till I can't boot. I use Prime95 blend test. How can I test if my settings are usable for normal use? 3Dmark06?

I can't believe I only have 35c with air, under load, I'm starting to doubt pc probe is giving me accurate readings. I'll install a bunch of other monitoring programs when I get home. If it's true though then I love my new Haf 932!

I think I'm using the yellow ones (recommend settings)! I have to read the forum more closely. I rather use black, especially if I get the dominators since my cpu heat sink partially goes over the yellow and I don't think they will fit.

I saw some forums with my board and I couldn't get it to pass prime95 with their settings... I don't remember if they stress tested or not.

Funny, I just remembered about cool and quiet today. One of the settings I had wouldn't even post so I had to reset my bios. I forgot to check those settings! If they are enabled by default, then they are enabled now.


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## Guyonskis (Jun 17, 2009)

Fatal said:


> Which slots are you using the ram in? I think I read in those links I sent you that the black ones were better to use.



Where did you see this? I can't find it.


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## cdawall (Jun 17, 2009)

no bus clock issues on my M4A78T-E


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## suraswami (Jun 17, 2009)

Guyonskis said:


> So when I read about people claiming 3.8, it just means that they can boot windows? THAT has never been an issue... I haven't tested how far I can go till I can't boot. I use Prime95 blend test. How can I test if my settings are usable for normal use? 3Dmark06?
> 
> I can't believe I only have 35c with air, under load, I'm starting to doubt pc probe is giving me accurate readings. I'll install a bunch of other monitoring programs when I get home. If it's true though then I love my new Haf 932!
> 
> ...



My 720BE can boot into windows stable @ 3.8G with 1.45v, can do basic tasks like IE etc.  More than that crash.  This same chip I bought from cda did 4Ghz @ stock volts on his Asus.  I guess I am good with a $80 board 3.8G vs $200 board clocking @ 4ghz.

I wouldn't push anything past 3.6Ghz for everyday use @ no more than 1.4v.  That extra 200Mhz is not going to make any difference in games anyway, may be media tasks but I can wait for extra 2 minutes to finish up the task.

I keep mine @ 3.5Ghz for daily use, tho the cpu is 3.6Ghz stable whatever I throw at it except S3 wake up.

my 2 cents.


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## Guyonskis (Jun 17, 2009)

I tried similar settings (low cpu multiplier, x8 NB, similar vcore) and I couldn't even POST. I won't try it that high again. I couldn't do 1:2 with my ram with that bus however so I aimed for 1:1, with a manual setting of 7XXMhz (don't remember exactly). I'm not sure what went wrong.


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## Guyonskis (Jun 17, 2009)

suraswami said:


> My 720BE can boot into windows stable @ 3.8G with 1.45v, can do basic tasks like IE etc.  More than that crash.  This same chip I bought from cda did 4Ghz @ stock volts on his Asus.  I guess I am good with a $80 board 3.8G vs $200 board clocking @ 4ghz.
> 
> I wouldn't push anything past 3.6Ghz for everyday use @ no more than 1.4v.  That extra 200Mhz is not going to make any difference in games anyway, may be media tasks but I can wait for extra 2 minutes to finish up the task.
> 
> ...



GTA4 is very sensitive and I get 50fps at 3.7Ghz with mediocre settings. Such a POS game (programming wise). Otherwise I agree that it doesn't make that much of a difference. I just think it's fun to see how far I can push my hardware... and my $160 board should handle more!


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## cdawall (Jun 17, 2009)

Guyonskis said:


> I tried similar settings (low cpu multiplier, x8 NB, similar vcore) and I couldn't even POST. I won't try it that high again. I couldn't do 1:2 with my ram with that bus however so I aimed for 1:1, with a manual setting of 7XXMhz (don't remember exactly). I'm not sure what went wrong.



what were your HTT volts?


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## Fatal (Jun 17, 2009)

Guyonskis said:


> So when I read about people claiming 3.8, it just means that they can boot windows? THAT has never been an issue... I haven't tested how far I can go till I can't boot. I use Prime95 blend test. How can I test if my settings are usable for normal use? 3Dmark06?
> 
> *Prime95 is old and outdated lol most use OCCT. Far as if it stable 1 hour of that OCCT most have different views. Will be 100% stable in 7 hours of OCCT. I have only ran it for 1 and have not BSOD.*
> 
> ...



Well I think I read that use black slots wrong I cant find it now


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## Guyonskis (Jun 18, 2009)

I downloaded OCCT and SpeedFan... 37C idle - 48C load at 1.5v. I think that's still safe. I only used PcProbe before... probably why my old cpu is fried. I hope I didn't damage my board in the old case either. 

CPUID is showing strange voltages... 4.86 for +12v, -10.3 for -12v. I think my mobo gave something different. How do you upload pictures?

@cdawall my HTT is on auto. I upped it for one test and it didn't make a difference. 

I bought the dominator memory. 206x18 failed OCCT in seconds. I don't think memory is the issue.


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## Steevo (Jun 18, 2009)

Guyonskis said:


> GTA4 is very sensitive and I get 50fps at 3.7Ghz with mediocre settings. Such a POS game (programming wise). Otherwise I agree that it doesn't make that much of a difference. I just think it's fun to see how far I can push my hardware... and my $160 board should handle more!



I doubt your CPU is holding you back as mine runs the game at max settings and only uses 60% of the CPU, the game really requires VRAM to work well. 

Statistics
Average FPS: 42.89
Duration: 37.33 sec
CPU Usage: 50%
System memory usage: 64%
Video memory usage: 90%

Graphics Settings
Video Mode: 1920 x 1200 (59 Hz)
Texture Quality: High
Texture Filter Quality: Highest
View Distance: 32
Detail Distance: 70

Hardware
Microsoft Windows 7 Ultimate 
Microsoft Windows 7 Ultimate 
Video Adapter: ATI Radeon HD 4800 Series 
Video Driver version: 8.14.10.662
Audio Adapter: Speakers (SoundMAX Integrated Digital HD Audio)
AMD Phenom(tm) II X4 940 Processor

File ID: benchmark.cli


4850 1GB and limited by my VRAM speed, more core speed doen't make shit difference.


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## Guyonskis (Jun 18, 2009)

So I upped my vcore to 1.55v. 18x206 and 18.5x200 seems to be stable, 19x fails after about a minute. I`ll play around with it and see how high I can get. Weird that I need so much more volts then you guys. I still haven`t pushed it to not boot windows... maybe I`ll try that later. 1.55v gives 51C core under load. I read that the phenom 940 can go up to 62C... should I push it higher then 1.55v?


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## Fatal (Jun 18, 2009)

Guyonskis said:


> So I upped my vcore to 1.55v. 18x206 and 18.5x200 seems to be stable, 19x fails after about a minute. I`ll play around with it and see how high I can get. Weird that I need so much more volts then you guys. I still haven`t pushed it to not boot windows... maybe I`ll try that later. 1.55v gives 51C core under load. I read that the phenom 940 can go up to 62C... should I push it higher then 1.55v?



For 24/7 use no I wouldnt for bench runs sure. I have put 1.55v in my CPU once and have not every since. I wouldnt push it any higher than you have thats just me though. Its not worth it you have not been able to get any thing stable over 3.7 so why bother. 

To upload screen shots : http://www.techpowerup.org/ 

I have seen others with my same set up able to run 3.8-3.9 on air stable. Could just be the chip some dont over clock as good as others. I would try to get 3.7 since thats seems to be your goal. If not settle for 3.6 and do some tweaking there really isnt much a difference. 

I run mine at 3.600 and NB @2600 have you tried overclocking the NB yet? Load up some screen shots


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## Guyonskis (Jun 18, 2009)

This is the highest I could boot. Very unstable... voltage is actually 1.57v.


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## Guyonskis (Jun 18, 2009)

This is my current stable settings. Next I'll find the best combination to get the most out of my ram and I'll try to make the 7.9 more stable so I can bench. 






Thanks for all the help everyone! I've learned alot.


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## Fatal (Jun 18, 2009)

Thats great to hear looking forward to see some benchmarks


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## newguy05 (Sep 3, 2010)

Exeodus said:


> It has been my experience that ASUS boards don't overclock the bus very far past 200 on Phenom II class processors.  Most 940's seem to acheive max stability around 3.6ghz.  They will game and bench higher, but won't pass most stress tests.



i`v managed to reach 300 fsb on this phenom 2 720 thought i would share it with u guys...see attachments.


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## Fatal (Sep 3, 2010)

newguy05 said:


> i`v managed to reach 300 fsb on this phenom 2 720 thought i would share it with u guys...see attachments.



Sweet, have you run any benchmarks at that bus speed? What's your memory running at? I can get 266 bus with my chip. Reached 300 but was not stable at all I just clock with multi.


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## de.das.dude (Sep 3, 2010)

i got my 945 to 3.7, but it was best stable at 3.6. My HT and NB were at 2.4 and very stable. the voltages were upped a bit though.
click on my signature, it will take you to CPU Z with the 3.6GHz one done.

i guess the problem is due to stock cooling in my case. and i fixed my memory at DDR2 667, that way when OC-ing i had a lot of room.


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