HIS Radeon HD 7870 IceQ X Turbo Video Card Review

Product: HIS Radeon HD 7870 IceQ X Turbo
Company: HIS
Author: James Prior
Editor: Charles Oliver
Date: July 4th, 2012

Left 4 Dead 2

We played single player Hard Rain - Milltown, recording performance using FRAPS running at 1920x1080, highest settings with 4xAA/16xAF in-game and CCC Super Sampled Anti-Aliasing selected.



We ran the test at Eyefinity resolution using our 3 displays in Portrait configuration, increasing our resolution to 3240x1920 (plus bezel compensation).

CrossFireX Eyefinity:

Here we come to an interesting result. The Average FPS results reported above are not what FRAPS recorded, but instead are the effective FPS when taking in account microstutter. Microstutter was monsterous with this benchmark, with the average FPS recorded as 63FPS for CrossfireX, and 74FPS with the overclock applied. However, the stutter was pronounced (60%+) - quite unpleasant to play. In a simplistic test we'd just shrug and say 'bah, drivers!' but instead we decided to play around with settings a little bit. Rebenching using MSAA Adaptive AA mode (normal AA plus alpha texture AA) instead of SSAA we get very different results - 40FPS min and 77FPS average, and more importantly no stutter. Dropping to just in-game AA, the results are 124FPS min / 180FPS average. Clearly the problem isn't drivers, it's SSAA.

It would be interesting to see if PCI-E 3.0 slots would change the results, pointing to a bottleneck of data transfere between the cards, but we don't have the test bed to try that. If AMD equipped the Radeon 7800 series with dual CrossFireX edge connectors we could try 1 bridge vs. 2, but that's not the case, either. Given the 'high' minimum FPS rates it seems that memory bandwidth, not amount, is the limiting factor here, which is bourne out in the OC vs. stock results; 60% microstutter index for OC cards, 66% for stock.