PCShopTalk posted a review on the Ati Radeon HD 4830 Graphics Card.
A quote from the review:
“From what I have researched, I have seen that this 4830 video card has exactly the same PCB layout compared to the AMD stock 4850. Some people even tried to flash this card with the 4850 BIOS, hoping that they will recover the missing shader units. Most of them bricked their cards doing this and I do not recommend doing this to anyone. It seems that there are 2 possibilities : AMD has disabled them in hardware or they are simply missing.
Overall, I can recommend this card for people that want to save a little money and do not want to invest more money in a single card.
For optimal performance, I highly recommend users to buy another card and put it in a Crossfire configuration. This way, the problems with the graphic intensive games at low FPS will be solved.”
Ati Radeon HD 4830 Video Card Review


