2 GPUs on B450

89Sirius · February 1, 2021

Hi. I recently got into mining crypto and earned my first 100$ mining on my gaming pc. This motivates me to buy another gpu and increase my earning. Currently I'm mining with Rtx 2070. Will I be able to use 2 GPUs on my motherboard? My mobo is Gigabyte B450 Aorus Pro. I think I have my Rtx 2070 plugged in x16, and the gpu i want to buy would go in in x4 pci-e slot as far as I know. Will the speed of the new gpu be reduced if it's on x4? I would use it strictly for mining. Those are the slots it has:

1 x PCI Express x16 slot, running at x16 (PCIEX16)
* Actual support may vary by CPU.
* For optimum performance, if only one PCI Express graphics card is to be installed, be sure to install it in the PCIEX16 slot.
(The PCIEX16 slot conforms to PCI Express 3.0 standard.)
1 x PCI Express x16 slot, running at x4 (PCIEX4)
* The PCIEX4 slot shares bandwidth with the PCIEX1_1 and PCIEX1_2 slots. The PCIEX4 slot operates at up to x2 mode when the PCIEX1_1/PCIEX1_2 slot is populated. The PCIEX4 slot operates at up to x4 mode when both of the PCIEX1_1 and PCIEX1_2 slots are empty.
1 x PCI Express x16 slot, running at x1 (PCIEX1_2)
1 x PCI Express x1 slot (PCIEX1_1)
(The PCIEX4 and PCIEX1 slots conform to PCI Express 2.0 standard.

Thanks.

Mick Naughty · February 1, 2021

Won’t matter if it’s x16 or x4. It’s gonna mine the same. Nothing to worry about.
Only thing it would effect is the main card for gaming but only slightly. But that’s only if the slot of the second card runs off the cpu or chipset.

89Sirius · February 1, 2021

11 minutes ago, Mick Naughty said:

Won’t matter if it’s x16 or x4. It’s gonna mine the same. Nothing to worry about.
Only thing it would effect is the main card for gaming but only slightly. But that’s only if the slot of the second card runs off the cpu or chipset.

Thanks for the info.

linuxChips2600 · February 1, 2021

I was literally just gonna post a screenshot of the PCIE slots' specs but you already took the time to gather the info; good job .

But basically the specs mean that besides the main x16 slot capable of full x16 (which is almost guaranteed to be directly linked to the PCIE controllers on the CPU), you have another x16 which is capable of x4 only if that is the only other non-empty PCIE slot in your system (and is very likely linked to the chipset especially if you are using an NVME drive, as NVME drives are typically x4 electrically and directly linked to the CPU, and all Ryzen CPUs afaik only have 20 dedicated PCIE lanes total for various add-on PCIE devices).

A quick glance at a pic of your motherboard (if I found the correct pic) shows me that the x16 physical/x4 electrical slot is likely 2nd from the bottom, as otherwise it won't really make sense to have that many lanes available electrically for such a tight spot. Like others have said that should definitely not be a problem; I know Linus himself has showcased mining-oriented motherboards in the past where each GPU only needed to be connected to the motherboard via a x1 PCIE interface. But given what I said thus far, I'd advise you to not add even more PCIE devices to your mobo at this point if you are already using 2 GPUs unless if absolutely necessary, as that not only takes away lanes from your mining-only GPU (which I btw hope you don't actually end up using in your full x16 slot especially if you are going to do more PCIE bandwidth intensive stuff such as Cuda/Optix compute and rendering), but also restricts airflow inside your case even more (assuming you're using a standard-ish computer case).

Although stuffing all of your PCIE slots may not be a problem at least for most of the time, you could run into some degree (even if not a whole lot) of system bottlenecks if you decide to mine and game at the same time (especially as B450 is still PCIE 3.0 at the most). Even more importantly, if you also don't take into account properly your airflow configuration inside your case and your PSU wattage/capabilities, there could also be power "bottlenecks" and your GPUs could end up running much hotter that you'd like them to, to say the least. So make sure at the very least to pick a power-lite, efficient, and (relatively) inexpensive GPU like the 1660 super, and don't be afraid to undervolt and dial in a reasonable power limit so that you can keep the mining GPU running in the background with minimal to no impact on any other task you wish to do in the meantime with your gaming PC.

Hope my couple of cents was helpful.

89Sirius · February 1, 2021

43 minutes ago, linuxChips2600 said:

I was literally just gonna post a screenshot of the PCIE slots' specs but you already took the time to gather the info; good job .

But basically the specs mean that besides the main x16 slot capable of full x16 (which is almost guaranteed to be directly linked to the PCIE controllers on the CPU), you have another x16 which is capable of x4 only if that is the only other non-empty PCIE slot in your system (and is very likely linked to the chipset especially if you are using an NVME drive, as NVME drives are typically x4 electrically and directly linked to the CPU, and all Ryzen CPUs afaik only have 20 dedicated PCIE lanes total for various add-on PCIE devices).

A quick glance at a pic of your motherboard (if I found the correct pic) shows me that the x16 physical/x4 electrical slot is likely 2nd from the bottom, as otherwise it won't really make sense to have that many lanes available electrically for such a tight spot. Like others have said that should definitely not be a problem; I know Linus himself has showcased mining-oriented motherboards in the past where each GPU only needed to be connected to the motherboard via a x1 PCIE interface. But given what I said thus far, I'd advise you to not add even more PCIE devices to your mobo at this point if you are already using 2 GPUs unless if absolutely necessary, as that not only takes away lanes from your mining-only GPU (which I btw hope you don't actually end up using in your full x16 slot especially if you are going to do more PCIE bandwidth intensive stuff such as Cuda/Optix compute and rendering), but also restricts airflow inside your case even more (assuming you're using a standard-ish computer case).

Although stuffing all of your PCIE slots may not be a problem at least for most of the time, you could run into some degree (even if not a whole lot) of system bottlenecks if you decide to mine and game at the same time (especially as B450 is still PCIE 3.0 at the most). Even more importantly, if you also don't take into account properly your airflow configuration inside your case and your PSU wattage/capabilities, there could also be power "bottlenecks" and your GPUs could end up running much hotter that you'd like them to, to say the least. So make sure at the very least to pick a power-lite, efficient, and (relatively) inexpensive GPU like the 1660 super, and don't be afraid to undervolt and dial in a reasonable power limit so that you can keep the mining GPU running in the background with minimal to no impact on any other task you wish to do in the meantime with your gaming PC.

Hope my couple of cents was helpful.

Appreciate the long answer. I wont game and mine at the same time. I just leave the pc to mine overnight while i sleep or while I'm away. Im a temp monitoring freak and I undervolt all my gpus and cpu.. With my current gpu, rtx 2070, while mining, I went from 82 degrees (its a gigabyte with 2 fan and they have the worst cooling out of all rtx2070's so at full load its very hot) and 34 mh/s(stock hashrate) to 67 degrees and 43 mh/s with a power consumption of 123w. Also my psu is 750w so i guess it's ok. Since pretty much all is ok as you said, the only problem that remains now is finding a gpu that is not 5 times the normal price. I live in EU and in my country a rtx 3070 cost around 1200$ now in best case scenario. I will wait for the prices to go down although that may take a lot of time but it's good to know that my motherboard is able to support another gpu without loosing its mining performance. Thanks again !