Help, PCI-E x16 running as x8.

JCNiest5 · 05-21-2007, 12:21 AM

I've got an EVGA 7950 GX2 that is running in x8 (according to CPUZ) and I want it to run in x16 mode, where do I go about changing it? I've read a few posts of hints elsewhere which I've tried, but none seems to work. There is no option in the BIOS to set it to run in x16 mode. I've tried increasing the PCI-E FSB to 101 - 110 (as some hints advise) but that doesn't do the trick. There must be a way to do this. This is on an Asus P5B Deluxe WiFi-AP board. Thanks....

Kimbo · 05-23-2007, 10:22 AM

i have no absolute idea, as a 16x pci-e card on a 16x pci-e slot should run at 16x. if i had to guess i'd say because the 7950 gx2 is actually 2 cards molded into one as it were, maybe they each run at 8x in their own right making it a total 16x. know what i mean ? your card is a funny one like that...

shaihulud · 05-23-2007, 12:08 PM

Well, the way I do understand it is this: There is a 48 lane PCIe switch. Divide by three and you have 16 lanes to allocate to each interface. This being the two cards PCIe interface to the main PCIe interface to the motherboard. Divide by 2 due to the fact that it is bidirectional and you have an x8 connection for all interfaces.

This is the way it is and is not only a bit disconcerting, but misleading also.

Edit: Let me clarify something because I was a bit ambiguous. According to CPUz the interface is x8. The 16 lanes from the interface are split between the two GPU’s. According to logical diagrams it is x16 from the interface to the switch, but for both cards, so divide by two. You have 8 lanes going from the interface to the switch, then another two 8 lanes from the switch to each GPU and also 8 lanes going to each GPU from the GPU.

---x16 Interface---][x8<--->Switchx8<--->GPU0<---x8 to--->GPU1
---x16 Interface---][x8<--->Switchx8<--->GPU1<---x8 to--->GPU0

Kimbo · 06-06-2007, 12:55 PM

hello original poster ???????

05-21-2007, 12:21 AM	#1
JCNiest5 Computer Maniac Join Date: Jan 2003 Location: The Twin Boys, MN. Posts: 1,387	Help, PCI-E x16 running as x8. I've got an EVGA 7950 GX2 that is running in x8 (according to CPUZ) and I want it to run in x16 mode, where do I go about changing it? I've read a few posts of hints elsewhere which I've tried, but none seems to work. There is no option in the BIOS to set it to run in x16 mode. I've tried increasing the PCI-E FSB to 101 - 110 (as some hints advise) but that doesn't do the trick. There must be a way to do this. This is on an Asus P5B Deluxe WiFi-AP board. Thanks.... __________________ Asus Rampage 2 Extreme, Intel i7 920, 6GB (3x2GB) Corsair DDR3-1333, EVGA 8800GTS 320MB Asus P5B Deluxe Rev. 1.10G, Dual Core E2200, 2GB OCZ Platinum Rev. 2 (2x1GB), EVGA 8500GT 1GB DDR2 Gigabyte GA-945GCM-S2C, Dual Core E2180, 2GB OCZ Platinum Rev. 2 (2x1GB, PNY8600GT 256MB DDR3 ECS 945GCT-M/13333, 1GB, EVGA 8400GS Abit KN8 Rev. 1.1, A64 4000+, 1GB G.Skill PC-3200 (2x512MB), MSI 8500GT 256MB DDR3 Last edited by JCNiest5 : 05-21-2007 at 09:08 AM.
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05-23-2007, 10:22 AM	#2
Kimbo [PC Gamer] Join Date: Nov 2001 Location: Perth, W.A. Posts: 617	i have no absolute idea, as a 16x pci-e card on a 16x pci-e slot should run at 16x. if i had to guess i'd say because the 7950 gx2 is actually 2 cards molded into one as it were, maybe they each run at 8x in their own right making it a total 16x. know what i mean ? your card is a funny one like that... __________________ § Pimp of Mario's World. Hater of society. §
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05-23-2007, 12:08 PM	#3
shaihulud Registered User Join Date: Jan 2005 Posts: 1,254	Well, the way I do understand it is this: There is a 48 lane PCIe switch. Divide by three and you have 16 lanes to allocate to each interface. This being the two cards PCIe interface to the main PCIe interface to the motherboard. Divide by 2 due to the fact that it is bidirectional and you have an x8 connection for all interfaces. This is the way it is and is not only a bit disconcerting, but misleading also. Edit: Let me clarify something because I was a bit ambiguous. According to CPUz the interface is x8. The 16 lanes from the interface are split between the two GPU’s. According to logical diagrams it is x16 from the interface to the switch, but for both cards, so divide by two. You have 8 lanes going from the interface to the switch, then another two 8 lanes from the switch to each GPU and also 8 lanes going to each GPU from the GPU. ---x16 Interface---][x8<--->Switchx8<--->GPU0<---x8 to--->GPU1 ---x16 Interface---][x8<--->Switchx8<--->GPU1<---x8 to--->GPU0 Last edited by shaihulud : 06-06-2007 at 03:23 PM.
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06-06-2007, 12:55 PM	#4
Kimbo [PC Gamer] Join Date: Nov 2001 Location: Perth, W.A. Posts: 617	hello original poster ??????? __________________ § Pimp of Mario's World. Hater of society. §
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