Thursday, October 23rd 2008
Shader-deficient Radeon HD 4830 Could be in the Channels
The ATI Radeon HD 4830, the newest foot-soldier from the red-camp, is AMD's answer to the GeForce 9800 GT, a gap left by the company, that may have been eating into its profits for months now. As usual, TechPowerUp received its review samples from TUL (PowerColor), AMD's long-standing partner, and AMD itself. We reviewed both of them, as soon as the product became official today. During the course of reviewing them, with the card from AMD in particular, our reviewer, W1zzard noticed an anomaly: the sample from AMD was showing an abnormal stream processor count of 560.
W1zzard also authors the GPU-Z diagnostic utility, and it is his routine chore to program the utility to detect a new GPU. The newest build of GPU-Z detected the card from AMD to have as many as 80 stream processors disabled from the original specifications for the Radeon HD 4830. In his article, W1zzard attempts to explain this anomaly.
The RV770LE graphics processor (GPU) is a "lite" version of the RV770 GPU that went into making the Radeon HD 4850. Out of the 800 stream processors (SP) the RV770 has, AMD carved out the new GPU by disabling two blocks of 80 SPs each, resulting in a 640 SP-laden Radeon HD 4830. Earlier, GPU makers would simply make a BIOS edit that disabled blocks of shader units. Both NVIDIA and AMD these days, resort to physically modifying the GPU, making irreversible changes to the amount of SPs available for the GPU to use. On the sample TechPowerUp got from AMD, there were three such blocks (perhaps accidentally) disabled, crippling the SP count further down to 560.
This did reflect in the card's performance against the one PowerColor sent based on the same GPU. The card from PowerColor outperformed the reference card due to its "proper" stream processor count. We urge reviewers and enthusiasts to verify the stream processor counts of their Radeon HD 4830 samples or products using the aforementioned build of GPU-Z.
W1zzard also authors the GPU-Z diagnostic utility, and it is his routine chore to program the utility to detect a new GPU. The newest build of GPU-Z detected the card from AMD to have as many as 80 stream processors disabled from the original specifications for the Radeon HD 4830. In his article, W1zzard attempts to explain this anomaly.
The RV770LE graphics processor (GPU) is a "lite" version of the RV770 GPU that went into making the Radeon HD 4850. Out of the 800 stream processors (SP) the RV770 has, AMD carved out the new GPU by disabling two blocks of 80 SPs each, resulting in a 640 SP-laden Radeon HD 4830. Earlier, GPU makers would simply make a BIOS edit that disabled blocks of shader units. Both NVIDIA and AMD these days, resort to physically modifying the GPU, making irreversible changes to the amount of SPs available for the GPU to use. On the sample TechPowerUp got from AMD, there were three such blocks (perhaps accidentally) disabled, crippling the SP count further down to 560.
This did reflect in the card's performance against the one PowerColor sent based on the same GPU. The card from PowerColor outperformed the reference card due to its "proper" stream processor count. We urge reviewers and enthusiasts to verify the stream processor counts of their Radeon HD 4830 samples or products using the aforementioned build of GPU-Z.
28 Comments on Shader-deficient Radeon HD 4830 Could be in the Channels
If its advertised as 640SP and then one you get is 560SP, you could take it back right?
the different cooler and fan control settings are what make the card quieter.
the heat output of the additional 80 shaders is not much .. a few watts i'd say
Also it's common sense that with less SPs working there's going to be less heat and lower fan speeds would be required. I know the fan speed (and the fan itself) is different in the two you reviewed and not based on SP number, but theory is still by my side. The difference might not be huge, but it'd be there for sure.
In the recent times performance is the only thing that I have found that can't be reduced to theories, you have to test them and looking at your reviews the conclusion is clrear. Clock for clock 560 SP RV770 performs almost on par with the 800 SP one. Even in F@H (real life shader heavy app) there's no difference, so as a personal preference I would take the 560 SP one.
I'm not apologizing for them and I understand there might be many factors that could lead to those differences, but I am pretty much only talking about the two cards you reviewed. Between the two I like the 560 SP one better.
and review samples are work-in-progress/engineering samples like the one from AMD
and the one from TUL (PowerColor) was a Retail i asume that had correct numb3rs of shaders
Even with 560 shaders, the performance is great. And they needed a gap between 4830 and 4850 and 4870 to warrant pricing in "different market segments".
I'm sure they werent expecting a genius like w1zzard to spot that so early on.
There is no way this was "a mistake". A GPU manufacturer isnt going to do a simple math mistake about the number of shaders on/off.
Having worked in inventory for many years, this sounds like a mix up between the sales and shipping/inventory folks.:o
This will be interesting to see if we're right. But, it may also be an attempt to market a lower power/sound card for the quiet crowd who still want some gaming. $100 card with passive cooling?
From W1z's tests the AMD card got 219.8 fps and the powercolor got 250.5
219.8 / 250.5 * 100 = 87.74% or a 12.26% reduction in performance for the AMD card.
Or am I not understanding what you posted?
Thus my adding the last line to my post.
I was misunderstanding you.
My bad :D
But yeah, obviously in purely shader test like perlin noise, more shaders equals more performance and as Wizzard pointed out that perlin noise seems to be a very good benchmark as long as you only compare the same architecture.
Accordingly in a fillrate test pretty much only the texturing power will be shown.
In real world things change though, you need a balance. For instance I consider F@H a very good real world shader compute benchmark. As good as it can get in real world testing at least, and there the difference is small. (in real applications you will never be able to bypass other parts of the architecture.)
You could think that the more the better, and so it is as long as the are no drawbacks to that aproach. In my personal view the drawbacks in this case are enough (power consumption, heat, price) that I consider those extra shaders worthless. Not only on gaming where the difference between the cards (both HD4830s and HD4850) can be explained by the pure clock speed diference, but F@H shows almost no difference in performance (clock for clock) even when compared to HD4850 or HD4870, and IMHO that's unforgetable for an architecture that was supposed to be efficient. They should have just forget about the marketing division and release RV770 as they first devised it: with 640 SPs. But that's only my opinion.
www.pcgameshardware.com/aid,664481/Reviews/Radeon_HD_4830_New_AMD_graphics_card_reviewed/?page=5
Plus the performance is noticeable.:rolleyes: