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Advisory for users with RD790 based motherboards and PCIe 2.0 graphics cards


New Member
Jan 11, 2005
181 (0.04/day)
Toronto ON
Processor i7 x980
Motherboard Asus SuperComputer
Memory 3x 2GB Triple Channel
Video Card(s) 2x Tahiti
Storage 2x OCZ SSD
Display(s) 23 inch
Power Supply 1 kW
Software Win 7 Ultimate
Benchmark Scores Very high!

It has come to my attention that there are many owners of RD790/RS780 based motherboards that have mistakenly thought their PCIe 2.0 cards are actually working at PCIe 2.0 speeds.

Please check your CMOS settings and look for a setting called "Gen2 High Speed" (or something along the lines of that). If you have an AMI BIOS, it will most likely reside under:

RD790/RS780 Configuration -> PCI Express Configuration -> Port2 (Port2 is your main graphics slot closest to the CPU)

If you have an Award BIOS, you are probably out of luck as I have not found an equivalent setting (short of going into the NB port registers and doing it there...).

Once you locate that setting, please change it to "Auto". If "Auto" is not available, then "Autonomous" will be. The newer SBIOS should have "Auto", if it does not, it is using an older incorrect algorithm for PCIe 2.0 speed (it "should" work most of the time though but you may or may not notice system slowdowns).

I noticed that there are many manufacturers that set this option to "Disabled" as the "Optimized" default which is stupid in my opinion (who the heck is doing their qualification?). The report from Catalyst Control Center is not accurate as it only tells you its a PCIe 2.0 "capable" card but it might not actually be running at PCIe 2.0 speeds. Use GPU-Z instead as that will tell you the actual speed.

You also need a PCIe 2.0 graphics card as well ;)



Sold my stars!
Jul 16, 2007
9,595 (2.52/day)
Processor Amd Athlon X2 4600+ Windsor(90nm) EE(65W) @2.9-3.0 @1.45
Motherboard Biostar Tforce [Nvidia] 550
Cooling Thermaltake Blue Orb-- bunch of other fans here and there....
Memory 2 gigs (2x1gb) of patriot ddr2 800 @ 4-4-4-12-2t
Video Card(s) Sapphire X1950pro Pci-E x16 @stock@stock on stock
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thanks for the heads up! :toast: