[SOLVED] PCIe Slots / Slot calculation and allocation

[HollowHax]

Hello Eveyone!
I'm looking into some hardware. I actually need to replace my current mobo (asrock ab350 pro4) And I'm looking at the asrock B450M Pro4. Now I've been told that I shouldn't bother with a B series chip set and instead should go with an X series because in going with a B my GPU will only get 8 lanes of PCIe for it> The argument went as follows
20 lanes with CPU, 4 go to sata, 4 for m.2 slots (mine aren't used) with 12 remaining for GPU, which since its either 16 or 8 they just go to 8 causing bottle neck. as I agree with the math, I'm confused on the PCie usage. I found this

Details AMD B450 Mid-range Chipset Surface

We've mentioned the pending AMD B450 chipset details inn our Ryzen gen2 review already really, but two new slides surfaced showing the final details. ...

www.guru3d.com

.

and it only seems to net me an additional 2 lanes which would make it 14 instead of 12 and it would still only use 8 lanes since it can't use 14.

However I have also read here, that 16 will be used for GPU due to the 16 DGP in the CPU with the extra 4 for talking to the mobo chipset which then leaves those other lanes open.

my current rig is a ryzen 5 1500x 1 SSD sata 1 HDD sata 1gtx1060 and looking at the B450M pro4 mobo from asrock.

Can someone help naviagte the jungle of PCIE lanes? Should I get the x370 chipset instead of hte b450 (I'm on a tight budget and I don't need to spend more than I have to) I know its a difference of 50 or so dollars but it matters haha

 

[CountMike]

Hello Eveyone!
I'm looking into some hardware. I actually need to replace my current mobo (asrock ab350 pro4) And I'm looking at the asrock B450M Pro4. Now I've been told that I shouldn't bother with a B series chip set and instead should go with an X series because in going with a B my GPU will only get 8 lanes of PCIe for it> The argument went as follows
20 lanes with CPU, 4 go to sata, 4 for m.2 slots (mine aren't used) with 12 remaining for GPU, which since its either 16 or 8 they just go to 8 causing bottle neck. as I agree with the math, I'm confused on the PCie usage. I found this

Details AMD B450 Mid-range Chipset Surface

We've mentioned the pending AMD B450 chipset details inn our Ryzen gen2 review already really, but two new slides surfaced showing the final details. ...

www.guru3d.com

.

and it only seems to net me an additional 2 lanes which would make it 14 instead of 12 and it would still only use 8 lanes since it can't use 14.

However I have also read here, that 16 will be used for GPU due to the 16 DGP in the CPU with the extra 4 for talking to the mobo chipset which then leaves those other lanes open.

my current rig is a ryzen 5 1500x 1 SSD sata 1 HDD sata 1gtx1060 and looking at the B450M pro4 mobo from asrock.

Can someone help naviagte the jungle of PCIE lanes? Should I get the x370 chipset instead of hte b450 (I'm on a tight budget and I don't need to spend more than I have to) I know its a difference of 50 or so dollars but it matters haha

Main PCIe lanes come from processor.

 

[HollowHax]

Main PCIe lanes come from processor.

So I guess i need a crash course in how PCIE lanes are used,

If my Ryzen 5 1500x only has 20 lanes, 4 for sata and usb, 4 for m.2 which means I have 16 left for gpu, would my gpu use all 16, and this other persons argument to me is nonsensical?

I guess I'm trying to understand how the PCIE lanes work and how they're utilized?

again I've always been more of a software guy and an amature hardware guy with only basic understanding

 

[CountMike]

So I guess i need a crash course in how PCIE lanes are used,

If my Ryzen 5 1500x only has 20 lanes, 4 for sata and usb, 4 for m.2 which means I have 16 left for gpu, would my gpu use all 16, and this other persons argument to me is nonsensical?

I guess I'm trying to understand how the PCIE lanes work and how they're utilized?

again I've always been more of a software guy and an amature hardware guy with only basic understanding

Yes, main PCIe lanes are from CPU but chipset may also have some too, CPU PCI lanes are mostly used on main PCIe devices/slots like first PCIe x16 slot and that's why in your example you can have all 16 lanes in first PCIe slot for your GPU. In most MBs, second PCIe x16 slot also shares same lanes so if you use both for let's say GPUs each one gets x8 ie. 8 lanes. Other slots may use lanes from chipset and will not cut down on number of primary (CPU) lanes but they usually rabge from 1 to 4 depending on chipset and BIOS.

 

[HollowHax]

Yes, main PCIe lanes are from CPU but chipset may also have some too, CPU PCI lanes are mostly used on main PCIe devices/slots like first PCIe x16 slot and that's why in your example you can have all 16 lanes in first PCIe slot for your GPU. In most MBs, second PCIe x16 slot also shares same lanes so if you use both for let's say GPUs each one gets x8 ie. 8 lanes. Other slots may use lanes from chipset and will not cut down on number of primary (CPU) lanes but they usually rabge from 1 to 4 depending on chipset and BIOS.

So
Let me see if I have this right.

CPU has 20

My board's PCie x16 has 1 gpu in it therefore I get 16 lanes.
if I had 2 PCIE x16 each with a gpu each gpu would have 8

4 lanes on CPU left right, those 4 are used for?

my mobo chip set has 6 pcie lanes

so I have 10 left, those are split between sata and other pcie slots right?

Sorry I think I'm starting to get it

 

[CountMike]

So
Let me see if I have this right.

CPU has 20

My board's PCie x16 has 1 gpu in it therefore I get 16 lanes.
if I had 2 PCIE x16 each with a gpu each gpu would have 8

4 lanes on CPU left right, those 4 are used for?

my mobo chip set has 6 pcie lanes

so I have 10 left, those are split between sata and other pcie slots right?

Sorry I think I'm starting to get it

You got it, those 4 lanes left from CPU are usually used for first (or only) M.2 slot for NVME SSDs.

 

[HollowHax]

You got it, those 4 lanes left from CPU are usually used for first (or only) M.2 slot for NVME SSDs.

Thanks,

I just wish I knew why this other person was trying to talk me out of B450 chipset and get the x370, the extra 2 lanes won't make much of difference for me, I'm only running 1 GPU so I'm not sure why he thought I'd be short PCIE lanes and only have 12 left for the GPU therefore cutting it to preform on only 8 lanes.

the only PCIE device in my pc would be the video card, I run hardware so no wireless card, no sound card, no m.2 devices

CPU Ryzen 5 1500x
GPU GTX 1060 6gb
(new board would be asrock b450m pro4, on a budget at the moment as I was one of the fools who bough the ab350 pro4 that were famous for loosing power randomly)
2 4 gig sticks of corsair ddr4 2400 mhz ram
1 ssd via sata
1 hdd via sata

is he right, would I be cutting myself in half? If I am, I don't see it

 

[CountMike]

Thanks,

I just wish I knew why this other person was trying to talk me out of B450 chipset and get the x370, the extra 2 lanes won't make much of difference for me, I'm only running 1 GPU so I'm not sure why he thought I'd be short PCIE lanes and only have 12 left for the GPU therefore cutting it to preform on only 8 lanes.

the only PCIE device in my pc would be the video card, I run hardware so no wireless card, no sound card, no m.2 devices

CPU Ryzen 5 1500x
GPU GTX 1060 6gb
(new board would be asrock b450m pro4, on a budget at the moment as I was one of the fools who bough the ab350 pro4 that were famous for loosing power randomly)
2 4 gig sticks of corsair ddr4 2400 mhz ram
1 ssd via sata
1 hdd via sata

is he right, would I be cutting myself in half? If I am, I don't see it

MBs with 400 series chipset have another benefit, better memory management and with 2nd and 3rd gen Ryzen easy 3600MHz RAM which is not a small thing seeing how Ryzen thrives with fast memory.
Don't see a reason to worry about SATA either. So yes, you are better off with b450 as 300 series is obsolete anyway.