Sapphire Radeon HD 5970 2GB OC Edition Review

by Michael "SKYMTL" Hoenig     |     November 17, 2009

PCI-E x8 Performance Scaling

Many people ask us about the performance of today’s best cards in situations where the usual x16 PCI-E 2.0 bandwidth isn’t available. There are also plenty of older but no less capable P35 boards still being used that use the older PCI-E Gen1 slots whose x16 bandwidth roughly equals that of an x8 PCI-E 2.0 slot.

In this section we will be using the bottom x8 PCI-E 2.0 slot (x8 electrical / x16 physical) on the same Gigabyte EX58 UD5 motherboard used for all other testing. We will be running the same GPU-intensive tests as in the Extreme IQ Settings testing.

So what does this all mean? It seems that in certain cases, the lower bandwidth provided by a 2.0 PCI-E interface running at x8 or a PCI-E 1.1 slot running at x16 will bottleneck this card ALOT. In other situations where the card isn’t rendering for all its worth, there is still some performance loss but not as much. As such, if you are running an older board or hope to run two of these cards in Crossfire on a P55 / P45 board you should be aware that you will not be getting optimum performance.

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