# Insane VRAM overclocking



## RejZoR (Feb 1, 2015)

I'm wondering one thing about VRAM overclocking. I've pushed my HD7950's VRAM to 7000MHz effective frequency (1750MHz) and the card is working perfectly fine in games and feels ridiculously fast. And since I know these new cards have CRC checking of data in the memory, too high frequencies can actually result in decreased performance (because the card has to repeat the stuff till it gets the right data out).

However, during my testing, SiSoft Sandra VRAM bandwidth test and 3DMark2013 scores just kept on climbing. Same goes for the actual framerate in games.

This is an increase from 1250MHz (5000MHz) to whooping 1750MHz (7000MHz). It's what GTX 970 has on the PCB.

Am I just so incredibly lucky or is there some sort of measuring flaw in my testing methodology?

Btw, I'm overclocking by modding and flashing the BIOS, doing it with Afterburner makes the card very twitchy and inconsistent along with stability issues.


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## RejZoR (Feb 1, 2015)

No one?


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## KingPing (Feb 1, 2015)

I OC my 280X to 1800Mhz mem and 1125Mhz core (could OC to 1150Mhz before omega drivers).

I do OC the card with CCC.


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## RejZoR (Feb 1, 2015)

I've had it at 1800MHz as well and gave me extra 3GB/s of bandwidth per SiSoft Sandra results over 1750MHz, but like I said, I'm not sure if these results are valid. I mean, if VRAM can gos o high this easily, why they don't push it this high. Originally it was 1250MHz and that is laaaaame.


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## KingPing (Feb 1, 2015)

maybe they want to keep temps and fan noise below certain parameters, so they don´t push clocks so high. TBH most of the time i run the card at it stock clocks which are 1070/1600. OC it to 1125/1800 is nice but you gain only around 10% more performance. 

I guess that with the card you have they don´t push clocks that high in order to sell more expensive ones.


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## RejZoR (Feb 1, 2015)

Frankly stock card was way louder than it is now heavily overclocked, overvolted and I've tuned the fan curve so it is silent even under heavy load. Temps go higher, granted, but still within normal.


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## TRWOV (Feb 1, 2015)

My 7970 does 1710Mhz on the memory before artifacts show up. Manufacturers just play safe since overclocking isn't guaranteed. My old 6950 could barely hold a 50Mhz overclock.

Your testing is fine. If memory gets to the point of having to re-fetch data you'd see a loss in performance.


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## KingPing (Feb 1, 2015)

TRWOV said:


> My 7970 does 1710Mhz on the memory before artifacts show up. Manufacturers just play safe since overclocking isn't guaranteed. My old 6950 could barely hold a 50Mhz overclock.



True, OC varies a lot from card to card.


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## MrGenius (Feb 2, 2015)

My MSI 280X Gaming 3GB VRAM runs completely stable and artifact-free @ 1850MHz(+350MHz). It has Hynix GDDR5. My old MSI R6950 Twin Frozr III Power Edition/OC ran @ 1600MHz(+350MHz), just as flawlessly. IIRC it also had Hynix GDDR5.

What have we learned here? MSI cards with Hynix GDDR5 are where it's at for insane VRAM overclocking.


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## TheHunter (Feb 2, 2015)

my 780gtx has a dud vram OC, its hynx and it can't do 7ghz unless i drop main gpu freq. a lot.. Max it can do with gpu OC 1215mhz is ~150mhz.

Saw same thing on 580gtx, only 570gtx somewhat OC'ed better with Samsung ram but in end it started to have issues, even @ stock OC (after ~ 2years)..


I would keep an eye on that uber OC, or at least not run it there all the time..


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## MrGenius (Feb 2, 2015)

I've smoked the VRAM on a card like that too before(too high OC + too long). But that was way back in the GDDR3 days, with my Geforce 6800 Ultra OC.

I have an Arctic Accelero Extreme IV on my 280X, which should buy me some time at least.


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## kn00tcn (Feb 2, 2015)

let's see some benchmarks?


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## vega22 (Feb 2, 2015)

thats a great oc but how much impact on performance does it have?

i know from my 7950 that pushing the ram mattered very little to my final fps as the core was not really starved of memory bandwidth anyway.

a trend which is very much teh same for my 290x as going past 1350 up to 1550 gains very little fps too. past that i see drops in perf as the ecc kicks in till it artifacts near 1600.

still impressive clocks one the less dude


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## MrGenius (Feb 2, 2015)

Well, I'm sorta in between rigs at the moment. I'm upgrading from a G33/ICH9 with an E8600, to a P67 with a i5 2400. Within the next month or so. Then there's the issue with 3DMark(all since Vantage) not showing my benchmark scores on the same page as the run details(like it used to). Hopefully ditching Vista for 7 is going to solve that.

In the mean time, for what it's worth, here's what a decent GC does with a crappy cpu on a crappy mobo.


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## MrGenius (Feb 9, 2015)

Heaven, Ultra/Extreme settings, 1080p @ 1150/1850



Valley, Extreme HD preset, 1080p @ 1150/1850


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## Cheeseball (Feb 9, 2015)

I bet if you clock that E8600 to at least 4.0 GHz you'll score 10 to 15 more FPS on Heaven. I used to get that much with a E8400 with a 8800GTS 512.


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## MrGenius (Feb 10, 2015)

I would....BUT I just got my X5470. Which, being literally 2x the processor, is going to smoke any possible 4GHz E8600 scores, probably without even overclocking it. But I'm still trying to score the right LGA775/771 mobo to overclock it good and proper(4GHz+) none-the-less. Then I'll do some comparison benching. I've got an idea which mobo should do the trick...we'll see. Until then, the cheapest G33/ICH9 I could find is still going to have to do.

BTW, I haven't scrapped the i5 upgrade plans, just got some money burning a hole in my pocket...so to speak. It's already a half-completed project. Still need 1 CPU + 1 mobo.

NOTE: Any scoring comparison should take into account it being compared to my ancient PCI-E 1.0 setup.


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## Tallencor (Feb 11, 2015)

My card. Hynix mem. 7870xt sapphire. Stock 975/1500. Running 1200/1500 for normal gaming. All benchmarks/Reviews say that clocking the mem on this card past 1520 dropped performance. But while I play inquisition I run 1220/1560 and it helps to push past the sluggish fps threshold.( on the settings I use) I had the core at 1200 and the mem at 1600 but after playing for 5-10 mins it would lockup on me (black screen). Temps were fine on the vrm's @ 81 ish. This is all with using trixx. What a diff the extra 100 mhz made though. ( smooth camera movement etc.) wish I could hold it. but alas. I wonder if the modding the bios would help? Like the op.


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## RejZoR (Feb 11, 2015)

VRAM overclocking helps massively for high resolution, high texture capacity loads. For framerate for everything else you need higher GPU clock.


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## Mathragh (Feb 11, 2015)

My 7950 VRAM also overclocks quite nicely, can run it at 1775, although i usually have it clocked a tad lower.
Core clocks are around 1150-1180 depending on the application.

I recon there is so much headroom mainly because we've got the right manufacturer (Hynix), and because lower rated chips we got often have the same headroom as higher rated chips because of the maturity of GDDR5.
That and the robustness of the tahiti memory controller.


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## MrGenius (Feb 11, 2015)

The funny thing about the VRAM with my 7970GHz/280X is, it likes to be overclocked almost to the point that it starts throwing black screens(crashing the display driver). Or not overclocked at all(or more than it already was from the factory). Meaning the stock VRAM frequency of 1500MHz, or overclocked to 1850MHz are where I find the most stability with this card. Anywhere in between causes problems. I swear I'm not making that up. And I haven't seen any artifacting result from having it(VRAM) clocked at any speed. It'll either run smooth at whatever MHz, or it won't run at all(or for very long w/o crashing). Not making that up either.

Here's some higher VRAM OC results.

Heaven, Extreme preset, 1600 x 900, 1175/*1870*


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## ChristTheGreat (Feb 11, 2015)

RejZoR said:


> I'm wondering one thing about VRAM overclocking. I've pushed my HD7950's VRAM to 7000MHz effective frequency (1750MHz) and the card is working perfectly fine in games and feels ridiculously fast. And since I know these new cards have CRC checking of data in the memory, too high frequencies can actually result in decreased performance (because the card has to repeat the stuff till it gets the right data out).
> 
> However, during my testing, SiSoft Sandra VRAM bandwidth test and 3DMark2013 scores just kept on climbing. Same goes for the actual framerate in games.
> 
> ...



personally I only had issue with Msi AB. I was overclocking my HD7950 by CC, same for HD7970. I modded the bios to up the limit in CC, so I could send 1400/2000 (but not reaching it)

Highest I went with my HD7950 was 1125 or 1150 and 1350mhz memory.. HD7970 was more 1150/1500 without any voltage modification.

1750 on your card, is that with stock voltage? that is a nice overclock.


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## Tallencor (Feb 12, 2015)

I'm Def playing with this tonight.


MrGenius said:


> The funny thing about the VRAM with my 7970GHz/280X is, it likes to be overclocked almost to the point that it starts throwing black screens(crashing the display driver). Or not overclocked at all(or more than it already was from the factory). Meaning the stock VRAM frequency of 1500MHz, or overclocked to 1850MHz are where I find the most stability with this card. Anywhere in between causes problems.


This may sound stupid but I wonder if Vram works like reg ram in that it has multiple stable clock steps. You know 1333, 1600, 1866? Someone should call sapphire for me.


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## brandonwh64 (Feb 12, 2015)

My 7970 does 1500Mhz on stock volts and is happy. I can get to 1750 but takes a small voltage bump


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## Tallencor (Feb 12, 2015)

Um.
http://www.ncix.com/detail/msi-radeon-r9-290x-gaming-df-92892-1509.htm
Say whaaaaaaa!?


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## EarthDog (Feb 12, 2015)

Id call it typical...


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## MrGenius (Feb 12, 2015)

Tallencor said:


> This may sound stupid but I wonder if Vram works like reg ram in that it has multiple stable clock steps. You know 1333, 1600, 1866? Someone should call sapphire for me.


Good question. I was originally thinking, since the VRAM voltage isn't software adjustable on my card, perhaps they've given me just enough volts to stabilize @ 1850MHz, yet not too much to keep it stable @ 1500MHz. Though, after some invenstigating on the matter, I'm now thinking there's probably quite a bit more to it than that. I've just found some very interesting info on what's technically refered to as _clock frequency and data rate scalability_. I mean it actually runs just as stable @ idle too(300MHz). So what's with that? Someone should definitely call Sapphire...for us both.

But until then, here's a quote from page 8 of the Qimonda GDDR5 –White Paper 2007 to help explain what I'm talking about.



> *7. GDDR5 Power management*
> 
> The GDDR5 is designed in a way to only consume power when really needed. Several features and methods are implemented in a way to allow a demand driven power management.
> 
> ...


 
Notice the terms "_*Extreme wide clock frequency range...*_" and more specifically "*...GDDR5 can be* _*gaplessly varied* *from 5 Gbps down to 200 Mbps (50 MHz clock frequency)*_.


Tallencor said:


> Um.
> http://www.ncix.com/detail/msi-radeon-r9-290x-gaming-df-92892-1509.htm
> Say whaaaaaaa!?


That's just how they've been labeling it lately. What they really mean by that is "1250MHz x 4".

MSI claims my 280X Gaming 3GB has even faster "_GDDR5 6000MHz Memory_". Which equals, as stated previously, the stock 1500MHz(x 4 since GDDR5 is "quad-pumped").
http://www.msi.com/product/vga/R9-280X-GAMING-3G.html#hero-overview


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## natr0n (Feb 12, 2015)

It all depends on vram chips used really.


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## Tallencor (Feb 12, 2015)

MrGenius said:


> That's just how they've been labeling it lately. What they really mean by that is "1250MHz x 4"


Meant the pricing and rebate.


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