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.
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28 Comments on Shader-deficient Radeon HD 4830 Could be in the Channels

#1
Pixelated
BIOS Hack

Do you think it's possible to hack the 4830 BIOS into enabling all of the SIMD units? According to Anandtech this is all AMD did to reduce the number of shader units in the deficient 4830's that some reviewers received. A BIOS tweak and maybe we have a 4850 for $125. This would really kill the 9600GT and 9800GT if this were possible somehow.

Or maybe even flash a 4850 BIOS straight onto the 4830, provided that the timings are the same

You can see the AMD statement to Anandtech here at the very top of the page

http://www.anandtech.com/video/showdoc.aspx?i=3437&cp=5#comments
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