Hi vogons. A few days ago I pulled out my Asus P5K64-WS (Intel P35 / 775 / DDR3) board to setup some crossfire benchmarks - but to my surprise, all 4 PCI-E slots are stuck running at 4x speed with one or two cards, it doesn't matter. As you can imagine, that gives a noticeable performance penalty in benchmarks and games - 13600 pts in 3dmark06 for a HD4870 on the P5K64-WS with 1333MHz DDR3 and a Q9650 @ 3.6GHZ (FSB400) vs 14700pts on a Gigabyte P35-D3SR with the same CPU @ stock 3GHZ and 1066MHz CL5 DDR2 ram. In crossfire two radeon 4870's only manage 18100

Any ideas why the board is stuck running at 4x PCI-E? I inspected the motherboard for damage, found the 8 pin CPU power had a broken off +12v pin and replaced the whole connector with one off a dead Asrock Z77. I also found somebody replaced one of the MOSFETS on one of the CPU power phases, but the board seems to run very well with whatever CPU I throw at it - it can drive my Q9550 to 4GHz easily @ 1.4v and my Q9650 to 3.6GHz on stock voltage with only Load Line Calibration enabled in BIOS.

Looking at the manual, the top most blue PCI-E slot is supposed to provide x16 lanes and the 3 black ones x4 - but on my board the blue slot is stuck at x4 as well. There is no physical damage to the slot or the components around it, and I have cleaned it thoroughly with isopropyl alcohol and a hard brush.

Here's a link to the manual in case I missed something - https://theretroweb.com/motherboard/manual/e3 … db745030696.pdf

And here's a review that also tests crossfire - https://www.hexus.net/tech/reviews/mainboard/ … th-mobo/?page=5

Any help is appreciated.