* I would aim for pcie 3.0 x8 slot speed should be fast enough on Windows. If you use Linux pcie 3.0 x4 is already perfect.
* In mainboard manual specification you can check how fast the pcie slots run with all slots used by GPUs.
* AMD rx5700 and next gen nvidia GPUs released by end of the year will support pcie 4.0 which doubles bandwidth again when CPU supports it too. So x1 riser for pcie 4.0 would be good enough on Linux even for fast GPUs.
PCIE x speeds for F@H gpu crunching
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Re: PCIE x speeds for F@H gpu crunching
Most Intel and AMD consumer CPUs offer 24 PCIE lanes.
4 of them are locked to an IGP. Some earlier F-versions of the Intel Core I 3/5/7 CPUs, like the 9400F, 9100F, have no IGP, so those 4 extra lanes are available for use.
4 to 8 lanes are used internally (sata, USB, Wifi, m.2 slots, other hardware on the board (like PS2 slots, etc...))
This leaves 16 PCIE lanes + whatever lanes your motherboard manufacturer was nice enough to provide extra from either the 4 or 8 other lanes.
The primary GPU usually gets 16 or 8 lanes.
Secondary slot 8 or 4
Tertiary slot 4 or 1
and any additional slots get 1 lane.
m.2 slots can also get 1, 2 or 4 lanes, depending on slot type.
If your system has m.2 slots on board, you can also use them for GPUs.
In most scenarios, modern motherboards limit the amount of GPUs to 2. If you're lucky, 3.
You could get 6th and 7th gen boards, that still support 3 way sli, then you can get 3 or 4 GPUs working on them.
Or get a mining board, and your maximum will be close to 13 GPUs.
That's from hardware point of view. FAH only utilizes 10 (slot 0 to 9).
You could use the remaining GPUs for other programs.
4 of them are locked to an IGP. Some earlier F-versions of the Intel Core I 3/5/7 CPUs, like the 9400F, 9100F, have no IGP, so those 4 extra lanes are available for use.
4 to 8 lanes are used internally (sata, USB, Wifi, m.2 slots, other hardware on the board (like PS2 slots, etc...))
This leaves 16 PCIE lanes + whatever lanes your motherboard manufacturer was nice enough to provide extra from either the 4 or 8 other lanes.
The primary GPU usually gets 16 or 8 lanes.
Secondary slot 8 or 4
Tertiary slot 4 or 1
and any additional slots get 1 lane.
m.2 slots can also get 1, 2 or 4 lanes, depending on slot type.
If your system has m.2 slots on board, you can also use them for GPUs.
In most scenarios, modern motherboards limit the amount of GPUs to 2. If you're lucky, 3.
You could get 6th and 7th gen boards, that still support 3 way sli, then you can get 3 or 4 GPUs working on them.
Or get a mining board, and your maximum will be close to 13 GPUs.
That's from hardware point of view. FAH only utilizes 10 (slot 0 to 9).
You could use the remaining GPUs for other programs.
Re: PCIE x speeds for F@H gpu crunching
I have an i5-3427U which is using it's iGP. Because it contains an HD Graphics 4000, which can be enabled by installing the appropriate driver from intel.com, which I never did until today. I'm not sure if the presence of the driver steals 4 lanes but it shouldn't really matter because as a laptop, there's no slot for a dGPU. Out of curiosity, I started Afterburner and it says the iGP is running at about 10% while browsing, but things seem less responsive. I'm thinking of removing that (unused) Intel driver and expect that it will go back to software rasterization which, in fact, may be faster. Comments?
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Re: PCIE x speeds for F@H gpu crunching
Depending on where you got the driver.
Windows has drivers that are usually years old.
The most up to date drivers are found on the intel site.
With Intel drivers, your CPU offloads the graphics tasks to the GPU (iGPU).
Without the drivers, it'll just fall back on the MS provided drivers.
Windows 7 or higher, doesn't install generic VGA drivers anymore (I think), like the case on Windows 98 or older operating systems.
I don't think there are currently any 'rasterization' drivers that use the CPU to drive the desktop.
More than likely it uses the OS provided drivers.
Not sure why a system with drivers would be slower than a system without...
Windows has drivers that are usually years old.
The most up to date drivers are found on the intel site.
With Intel drivers, your CPU offloads the graphics tasks to the GPU (iGPU).
Without the drivers, it'll just fall back on the MS provided drivers.
Windows 7 or higher, doesn't install generic VGA drivers anymore (I think), like the case on Windows 98 or older operating systems.
I don't think there are currently any 'rasterization' drivers that use the CPU to drive the desktop.
More than likely it uses the OS provided drivers.
Not sure why a system with drivers would be slower than a system without...