Sapphire 1GB HD 4850 X2

Verdict: £40 cheaper than a 2GB version but considerably slower.

ATI's latest GPUs seem to love lots of local memory. In our last graphics card Labs test, a 1GB Radeon HD 4870 delivered between 7fps and 16fps more at higher resolutions than its 512MB equivalent. With this in mind, and having been impressed by Sapphire's sub-£300 2GB HD 4850 X2's high scores in our performance tests, we wanted to find out how the 1GB version fared.

The Sapphire 1GB HD 4850 X2 features two ATI Radeon HD 4850 GPUs, each of which has 800 stream processors clocked at the standard 625MHz. Each GPU has access to 512MB of GDDR3 memory (making 1GB of memory in total). Each GPU uses a 256-bit-wide interface and is clocked at the default 993MHz (1.986GHz effective), giving each GPU 63.6GB/sec of bandwidth. Much like the 2GB Sapphire HD 4850 X2, this 1GB version uses two 80mm fans and an aluminium heatsink. The fans are neither loud nor especially quiet. As the rear of the card is filled with four DVI outputs, the card can't exhaust heat directly out of the case.

The official Catalyst 9.1 driver doesn't support the HD 4850 X2, so we had to download the hotfix version from http://ati.amd.com/support/driver.html. We used this driver to test both this 1GB card and the older 2GB card.

Starting with Fallout 3, the performance difference between the cards was as conspicuous as an early 1990s raver dancing at Sunday mass. Playing the game at 1,680 x 1,050 with 2x AA and 4x AF, the 2GB card churned out a 55fps minimum, while the 1GB managed a 40fps minimum. We saw similar results at 1,920 x 1,200 with 4x AA and 8x AF; the 1GB card could only just play the game smoothly at a 27fps minimum compared to the silky-smooth 40fps minimum of the 2GB card.

The 2GB card recorded marginally higher minimum frame rates than the 1GB card in X3: Terran Conflict. However, the average frame rates of the 2GB card were much higher than those of the 1GB card. At 1,920 x 1,200 with 4x AA and 8x AF, the 2GB card hit a 92fps average, 25fps faster than the 67fps average managed by the 1GB card.

With the easier games out of the way, we fired up Crysis Warhead. We were surprised to find that the 1GB Sapphire couldn't play the game smoothly even at 1,280 x 1,024 with 2x AA, producing a minimum of 16fps. Even a 1GB HD 4870 can manage a minimum of 25fps.The 2GB 4850 X2 card produced playable frame rates at 1,280 x 1,024 and 1,680 x 1,050 (both with 2x AA). At the former resolution, the 2GB 4850 X2 maintained a respectable 28fps, while at the higher resolution, the card managed a 25fps minimum.

Moving on to Far Cry 2, we were shocked to find the performance of ATI's HD 4850 X2 cards has been destroyed by its new driver. Using Catalyst 8.12 gave us an extra 14-26fps from our 2GB card over that produced with the Catalyst 9.1 hotfix driver. Even with the poorer performance, the 2GB card was much quicker than the 1GB, which could only play the game smoothly at 1,280 x 1,024 with 2x AA. Hopefully, ATI will fix the driver issue in Catalyst 9.2.

It should come as no surprise to folders that the ppd produced by these ATI cards is considerably lower than the score you might expect from a similarly priced Nvidia card. Both cards managed 2,312ppd from project p5378, which was worth 511 points. We were unable to run a folding client on both GPUs, despite using a dummy plug or plugging screens into all four outputs. This 1GB card caused our test system to draw up to 266W from the wall while folding, and up to 300W while running the X3 test. The 2GB card produced a 276W peak system power draw when folding and a 340W peak when running X3.

Conclusion

Our testing has shown that the amount of graphics memory of an HD 4850 or HD 4870 card is just as important as the GPUs' clock speeds. The Sapphire 2GB HD 4850 X2 comprehensively spanked the Sapphire 1GB HD 4850 X2 in every game at every resolution, just as 1GB HD 4870 cards have consistently outperformed 512MB HD 4870 cards. The marked difference in the Warhead performance shows that it's worth spending the extra £40 for the 2GB card. Folding performance is far below Nvidia's standard for ATI cards, but if this isn't a concern then either a £210 1GB HD 4870 or a £285 2GB HD 4850 X2 will serve you well.