Two similar GPUs; why is one utilized less?

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Re: Two similar GPUs; why is one utilized less?

Postby MeeLee » Sat May 30, 2020 6:25 pm

Your 2060 shouldn't be restricted to 75% utilization, if it's using a PCIE 3.0 x4 slot (on Linux).
It would, if it operated at PCIE 2.0 x4 speed.

Removing a PCIE card wouldn't be able to add +4 PCIE lanes either.
But in Bios you can usually adjust the slot speeds; running the first slot a bit slower at x8, freeing some lanes for the second slot.

But first, I would try to find out what speed your second PCIE slot runs at (2.0, or 3.0?).
if it is 2.0, you'll need to run both slots at x8 speed.
Not all motherboards support x8 speeds or higher on the second slot; so if that's the case, and your second slot is PCIE 2.0, but you have an m.2 slot that operates at 3.0, you might want to get an m.2 to PCIE riser cable.

In rare occasions, you could run some intel motherboards at x8/x8/x4 configuration, when disabling nearly all SATA ports, the audio chip, the PS2 connector and Thunderbolt (if your board has any), and running a CPU without IGP.
Intel CPUs should all have 20-24 PCIE lanes, 4 of them are usually dedicated to the USB hub, SATA ports, on board wifi and LAN, etc... The other 4 to an IGP.

I personally run my PC from the Ethernet port, and use a hub router, to reduce the wifi signals in the house.
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Re: Two similar GPUs; why is one utilized less?

Postby bruce » Sat May 30, 2020 6:46 pm

Or maybe you have a plain PCI slot that would run WiFi.
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Re: Two similar GPUs; why is one utilized less?

Postby Joe_H » Sat May 30, 2020 6:50 pm

MeeLee wrote:Intel CPUs should all have 20-24 PCIE lanes, 4 of them are usually dedicated to the USB hub, SATA ports, on board wifi and LAN, etc... The other 4 to an IGP.


Which Intel CPUs would that apply to? I have an i7-7700K, it has 16 PCIe lanes supported by the CPU itself, not 20+. That is common for most of the Core i-series except top of the line chips that use server sockets such as 2066 instead of 1151 for example.

Some logic boards will provide more PCIe lanes through a bridge chip, whether those would be usable for a GPU depends on which bridge and what connections are provided. Those connections will have greater latency, and often are a prior generation PCIe than the main PCIe slots.
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Re: Two similar GPUs; why is one utilized less?

Postby markdotgooley » Sat May 30, 2020 10:14 pm

This is an AM4 board with a Ryzen 5 1600 AF 6-core. I need to look at the BIOS too, yes.
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Re: Two similar GPUs; why is one utilized less?

Postby markdotgooley » Sat May 30, 2020 10:24 pm

markdotgooley wrote:This is an AM4 board with a Ryzen 5 1600 AF 6-core. I need to look at the BIOS too, yes.

I set x8 for both slots on the BIOS. Got x8 for the primary slot. Still x1 on the other. I'll see if it helps to remove that WiFi card and do WiFi on a USB dongle. No hurry.

Next time I buy a processor and motherboard I'll try to get things with better behavior.
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Re: Two similar GPUs; why is one utilized less?

Postby bruce » Sun May 31, 2020 2:01 am

You have to figure out how the MB is going to divide up the CPU's lanes.

Scenario one: 16 lanes connected to one GPU and none are left for anything else. Scenario two: 8 lanes connected to the first GPU, 1 lane connected to the WiFi, and maybe 1 or 4 to the second GPU.
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Re: Two similar GPUs; why is one utilized less?

Postby MeeLee » Sun May 31, 2020 6:56 am

Joe_H wrote:
MeeLee wrote:Intel CPUs should all have 20-24 PCIE lanes, 4 of them are usually dedicated to the USB hub, SATA ports, on board wifi and LAN, etc... The other 4 to an IGP.


Which Intel CPUs would that apply to? I have an i7-7700K, it has 16 PCIe lanes supported by the CPU itself, not 20+. That is common for most of the Core i-series except top of the line chips that use server sockets such as 2066 instead of 1151 for example.

Some logic boards will provide more PCIe lanes through a bridge chip, whether those would be usable for a GPU depends on which bridge and what connections are provided. Those connections will have greater latency, and often are a prior generation PCIe than the main PCIe slots.


4 of these lanes are dedicated to the igp inside that CPU, and can't be freed.
You can only get them from select CPUs without igp.
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Re: Two similar GPUs; why is one utilized less?

Postby markdotgooley » Mon Jun 08, 2020 7:47 pm

markdotgooley wrote:
markdotgooley wrote:This is an AM4 board with a Ryzen 5 1600 AF 6-core. I need to look at the BIOS too, yes.

I set x8 for both slots on the BIOS. Got x8 for the primary slot. Still x1 on the other. I'll see if it helps to remove that WiFi card and do WiFi on a USB dongle. No hurry.

Next time I buy a processor and motherboard I'll try to get things with better behavior.


I finally got a cheap USB dongle for WiFi and removed the PCI WiFi card. I now do seem to be getting x4 bandwidth on the secondary slot when before I was getting x1.

At least for now, both GPUs are supposedly at over 95% utilization. We'll see if this continues, and if PPD rises.

Edit: 88% on the second card sometimes. Maybe less? Bandwidth on PCIe really seems to matter. I will try to get a CPU/motherboard combination next time that allows an x8 or higher PCIe 3.0 or better connection to each card. That second card is getting only a PCIe 2.0 connection at x4, it turns out. Cheapish motherboard, cheap CPU.
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