Hexus has the first review up for the Shapphire 4850 TOXIC card. The card comes with higher clocks then the stock 4850. As far as the test results, the TOXIC only beats the stock 4850 by around 5-6% of the performance. The only test where it seems to not beat the stock 4850 was with Crysis @ 1680X1050 DX10.
The main difference from the looks of the stock 4850, is Shapphire has added a custom cooler the the TOXIC 4850. With an ambient temperature between 22 C and 21 C the Shapphire 4850 TOXIC averaged 30C lower on idle and load temperatures were 16 C lower. That is a huge difference from the stock cooler.
