Threesome Crossfiring the Radeon HD4890

JUST TWO WEEKS prior to the expected launch of the Evergreen ATI RV870 series - otherwise known as the HD 5870 - it's clear that the new cards' performance may leave the current crop in the dust.

So, for those who bought the HD 4890 and don't exactly want to replace them yet with the new stuff, is adding more HD 4890 cards worthwhile now they're at fire-sale prices?

Here we test the double and triple-CrossFire - called TriFire - HD 4890 setup on an Asus Z7S-WS mainboard. It's a dual Xeon mainboard in ATX format which is overclockable somewhat.

The dual X5482 quad core Xeons (same speed and cores as QX9770, but two of them in total for eight cores altogether) are overclocked to FSB 1800 and 3.6GHz speed, with 8GB of quad-channel FBD-900 CL5 memory. Too bad that Asus killed off its workstation division - sorry, merged it into servers - and never made a successor with two Nehalem Xeons and dual GPUs in ATX format.

There are also two independent PCIe x16 v2 slots, as well as one PCIe x16 physically (but x4 only electrical signaling) slot for the third card. That means, the third card would be somewhat impaired in terms of system throughput.

So, we put together three Asus HD 4890 cards, all running at 900MHz GPU speed, and risked a house fire to check the 3DMark Vantage scaling between dual-GPU and tri-GPU setups. All tests were done using 64-bit Windows Vista Ultimate and the new Catalyst 9.8 drivers, running off the A-Data XPG 64GB SSD drive and on a 26-inch 1920x1200 display.

Since multi-GPU users would surely use top notch displays, I ran the Extreme benchmark mode only at the native 1920x1200 resolution.

Here are the dual GPU results...

... and the triple GPU results - notice, the CPU results are very close to the dual W5590 Nehalem Xeon we tested earlier.

Yes, it is far less than the 50-80-plus per cent hike you get out of going from one to two GPUs, but even getting 15 per cent more on a bus-constrained third card was beyond my expectation.

If instead you use a board like the Asus P6T7WS with four full x16 width slots, even a Quadfire 4890 setup may scale well, at least in benchmarks.

In summary, yes, it's worth it for those with a suitable mobo and who insist on sticking with the current GPU. µ