Retesting the Radeon HD 4830: Too Few SIMDs Enabled
by Derek Wilson on October 25, 2008 12:00 AM EST- Posted in
- GPUs
UPDATE: As certain as it seemed AMD was that no 560 SP 4830 boards had made it into the retail channel, it appears that they were, in fact, wrong. Fewer than 400 HIS Radeon HD 4830 boards made it into the channel. Here is the statement we recieved from AMD's Jay Marsden today:
AMD has identified that, in addition to reference samples of the ATI Radeon™ HD 4830 boards sent to media with a pre-production BIOS potentially impacting the card’s performance, a very limited number of ATI Radeon™ HD 4830 boards were released to market with the same pre-production BIOS. This is in no way hardware related, and an updated BIOS fully resolves the performance limitation.
Through consultations with AMD board partners, it has been determined with a high degree of certainty that fewer than 400 ATI Radeon™ HD 4830 boards from one AMD board partner, HIS, have reached the market with the pre-production BIOS incorrectly provided by AMD. As only a small number of HIS-branded ATI Radeon™ HD 4830 cards are impacted, we ask any customers that purchased an HIS-branded ATI Radeon™ HD 4830 to test the board using the GPU-Z utility (available at http://www.techpowerup.com/gpuz). If the GPU-Z utility reports fewer than 640 shaders, please visit the HIS website for information on how to update the card BIOS via a downloadable install utility.
We had thought that retail parts would be fused to a certain number of active SIMDs to avoid soft mods and that review samples were probably based on test/engineering hardware AMD was using when developing the final specs for the Radeon HD 4830. It seems that theory is out the window, but we will continue to provide updates as we learn more.
Thursday, AMD launched their newest RV7xx variant completing their line up in time for the holiday season. As is usual with a new graphics card launch, we published a review. The hardware looked good and offers gamers that really want to play games with good quality but don't need high resolution performance a solid money saving option.
But a number of curious things happened throughout the course of the day yesterday. We first noticed an interesting article from the makers of GPU-z. Techpowerup.com posted a story on the fact that their reference sample from AMD only enabled 560 SPs rather than the full 640 we were all promised.
We were certainly intrigued by this, so we picked up the updated GPU-z and it told us we also only had 560 SPs. Now, this isn't a common occurrence at all, and multiple other issues could have been at work. We wanted to hold off on commenting until we could learn what was really goning on and bring you the whole story. It took us a while to sort everything out, and with this issue out there it's understandable why AMD needed some time to track down the causes and potential effects of this problem.
All the details we have point to the missing SP problem being limited to review samples only. AMD's partners should not have this issue pop up in the wild. This is good news for consumers, and good news for AMD as well. We saw that the 4830 wasn't a bad part, but because our tests were run with 87.5% of the full compliment of SIMDs our numbers don't reflect the full performance potential the hardware has.
AMD got us an updated BIOS for the card and we have new numbers showing the performance improvement. We have updated our tests from the other day to better reflect the relative performance end users can expect.
It is also worth noting that AMD has supplied all their partners with an updated BIOS as well to cover the just-in-case scenario. They believe they know why this happened and so believe that there is no cause for concern over retail parts exhibiting this problem. But giving their partners a new BIOS is a good idea anyway as it covers all the bases.
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JAKra - Saturday, October 25, 2008 - link
Hi!I thought that these disabled SIMDs were fused off in the ASIC. What if you flash your HD4830 with an HD4850 BIOS or a modified one enabling all the SIMDs? The PCB looks the same, they use the same GPU.( I think )
Good old modding days are back: 9800SE to 9800XT, anyone? :D
Clauzii - Sunday, October 26, 2008 - link
Heh, I have that :D Still rockin' :DJAKra - Saturday, October 25, 2008 - link
Wehehe Marlin1975, you beat me to it. You won. :DDerekWilson - Saturday, October 25, 2008 - link
we'll have to look into that :-)Marlin1975 - Saturday, October 25, 2008 - link
Does this mean we might be able to just do a firmware flash and get a 4850 level performance??? :)Gary Key - Saturday, October 25, 2008 - link
I tried that on a retail card, no go.PrinceGaz - Saturday, October 25, 2008 - link
Did you down-clock the 4850 BIOS so that it was within the limits of the 4830 card? I'm thinking especially about the memory here which would be most likely to have problems at the 4850 clock-speed, unless you've already verified that your 4830 can run at the 4850 core and memory clocks. As an nVidia owner, I don't know what BIOS editing tools are available for AMD cards, but I doubt any have been tailored for the 4830 as it is brand new.Even if the 4830 could cope with 4850 clocks, there may well be other tiny but significant changes to the card components which mark it as a 4830 and prevent it being flashed with a 4850 BIOS. A modded 4830 BIOS with more than 8 blocks of 80 SIMDs enabled would therefore have the best chance of success, and may well be forthcoming now that AMD inadvertently made BIOSes with both 7 and 8 blocks enabled public, especially if combined with what can be ascertained from the 4850 BIOS. I wouldn't know where to start with BIOS editing (I can work with x86 assembly, but that is child's play compared to understanding proprietary BIOS code). Some people have produced utilities which can edit at least certain parameterrs in BIOS files, so it's possible a tool to select the number of SIMD blocks could be produced.
It's probably not worth the effort though as the 4850 is only slightly more expensive anyway, so even if you could up the SPs from 640 (8 blocks) to 800 (all 10 blocks), given the performance differences presented in this article by going from 560 (7 blocks) to 640 (8 blocks); you'd be lucky to add more than 10% at best-- and that's assuming your card actually has a core with all 10 blocks capable of working correctly. It's not like the good old days of the 9500 non-Pro which if you were lucky could have its pipelines upped from 4 to 8 (like a 9700 non-Pro) giving a staggering increase in performance.
It's obvious how AMD messed up with the card samples they sent out. The only possible explanation is that the 4830 was originally intended to have 560 SPs and the BIOS was designed with that limit. Late in development, serious price-drops of 9800GT cards and the like forced AMD to give their 4830 a bit extra umph to compete at the price-point they had already targeted it at. Whereas they could easily adjust any physical limitation of the hardware pretty much as it was leaving the fab if they do so (by disabling less blocks on those cores), it takes longer to modify the software and check it to a level they can be confident the card will actually function correctly, such that some review samples went out with the older BIOS.
As such, all 4830 card cores may well be limited to 8 functional blocks (including those samples sent out with a BIOS setting it to 7 blocks), but only AMD insiders would know.
Goty - Sunday, October 26, 2008 - link
Or maybe it was much less complex than that and AMD actually tried more than one configuration during testing and a batch slipped through the cracks once everything was finalized. Y'know, that whole Occam's Razor thing.iwodo - Saturday, October 25, 2008 - link
ATI deliberately sent out sample with worst results. Then give better bios for enabling proper performance to catch Nvidia Off Guard.SiliconDoc - Monday, January 19, 2009 - link
How about ATI did this because they are morons, the ATI division just caused another huge chargeout loss for AMD, so there's bad karma at ati , and this shows exactly why their drivers are so screwey and broken all over the place." We were in a hurry" - can you imagine ? Something as ignorant as the wrong bios applied - that really takes the cake.
Congratulations ati, you screwed up again - and no, your fanboys can't admit it, they think it's a masterous marketing plan to destroy nvidia...
ATI blew it again.
( They did do very well on this card though, it's the first one at the pricepoint it's at that I like from them - since there's no CUDA, no PhysX, no driver profiles, a bloated CCC bloated a bit less, - no I don't plan on picking one up. )
Yeah, despite the major, amatuer, almost laughable mistake - makes ya wonder if anyone is at home or in charge there, this is a nice card for the price right now.