[SOLVED] New 3.0 G series AMD APU paired with 4.0 B550

[Tingu]

Hi all. I'm Planning a new build. Just getting all my research together. So far this is what I've done up with...
CASE - Be quiet 500DX
Motherboard - MSI B550 Tomahawk.
RAM - Find 2x 16gb 3200 CL16 DDR4.
SSD - Samsung 980 PRO PCIe 4.0 M.2 Gen4 1TB
PSU - 700-750w ATX not picked one yet.

Now for the CPU I'm confused between the Ryzen 5600X or to wait for the upcoming 5600G APU. The latter makes more sense with the current GPU crisis. But the confusion is that the new G series spec are PCIE 3.0 compared to the 4.0 spec of the 5600X. Can anyone please tell me how this would affect the rest of the 4.0 set up? Thanks in advance.

 

[hotaru.hino]

It just means the maximum PCIe spec it can run at is 3.0.

 

[Tingu]

Thanks for the reply. But will my m.2 SSD still run at 4.0 or will that also be limited to 3.0?

 

[Tingu]

Edit: But will my m.2 SSD still run at 4.0 or will that also be limited to 3.0? - as the motherboard is 4.0

 

[Eximo]

The motherboard is not 4.0, only the CPU (If you get the right ones). Some of the slots on the board will be directly connected to the CPU.

APUs use part of their PCIe allotment to connect to the onboard GPU, so generally they only offer half to the x16 slot. Not sure on these new ones, having trouble finding a block diagram for them.

X570 chipset has PCIe 4.0 on all slots, though in that case, you would want a CPU with PCIe 4.0 as well, otherwise there might be a bottleneck with a PCIe 4.0 storage device.

 

[hotaru.hino]

Thanks for the reply. But will my m.2 SSD still run at 4.0 or will that also be limited to 3.0?

The CPU determines the effective maximum PCIe speeds you can use, as the CPU has the PCIe controller. So if the CPU tops out at PCIe 3.0, then everything effectively can only run at up to PCIe 3.0 speeds.

 

[logainofhades]

X570 chipset has PCIe 4.0 on all slots, though in that case, you would want a CPU with PCIe 4.0 as well, otherwise there might be a bottleneck with a PCIe 4.0 storage device.

Not if you run it in a chipset driven NVME slot. Top M.2 would be 3.0, due to CPU, but any other slot, on x570, would come from the chipset.

 

[Eximo]

Between things on the chipset, but the CPU's bandwidth would be limited, yes? So there would be an upper limit on what you could do with that arrangement.

I can't find any good diagrams of the layout, and those I can find just say PCIe. All I can find that says PCIe 3.0 is AMD's listing.

 

[Tingu]

So from what everyone has said, am I right in saying that if my chosen CPU (or APU) chip is only 3.0 then anything I connect to the x16 4.0 slot on the motherboard will only give me 3.0 speeds. But if I connect a 4.0 SSD in the m.2 4.0 slot, I will still get the full 4.0? Is that right?

 

[Eximo]

No, B550 does not have PCIe 4.0 on the chipset, only PCIe 3.0.

X570 has PCIe 4.0 on the chipset.

I don't know enough about how the chipset and CPU communicate to tell you if a PCIe 4.0 drive with a PCIe 4.0 chipset would offer any benefit with a CPU labeled as PCIe 3.0. But on B550 that connection is certainly limited to PCIe 3.0.

There is another thread where someone is showing the Cezanne mobile version showing a PCIe 4.0 connection to an RTX3060 mobile, so I have no idea what to believe.

 

[Tingu]

https://www.amd.com/en/chipsets/b550

I am 99% sure the b550 does support 4.0. unless I have misunderstood the spec. Please see the link above

 

[Tingu]

https://www.amd.com/en/chipsets/b550

Also see link above which is the actual board I'll be buying. Under expansion slots it mentions 4.0.

And oh I've just noticed it says in the footnote that 4.0 depends on the CPU installed.

 

[hotaru.hino]

So from what everyone has said, am I right in saying that if my chosen CPU (or APU) chip is only 3.0 then anything I connect to the x16 4.0 slot on the motherboard will only give me 3.0 speeds. But if I connect a 4.0 SSD in the m.2 4.0 slot, I will still get the full 4.0? Is that right?

It may claim to run at PCIe 4.0 speeds, but if it has to transfer anything to the CPU, RAM, or the GPU (since it's connected to the CPU), it will only do so at PCIe 3.0 speeds because CPU and chipset is connected with a 3.0 link.

 

[Tingu]

It may claim to run at PCIe 4.0 speeds, but if it has to transfer anything to the CPU, RAM, or the GPU (since it's connected to the CPU), it will only do so at PCIe 3.0 speeds because CPU and chipset is connected with a 3.0 link.

Yes of course, silly me. That explains everything now. I can't believe I didn't know that, but now that you mention it, it's as though I new that all along. Feel like banging my head against the wall.

 

[Tingu]

Yes of course, silly me. That explains everything now. I can't believe I didn't know that, but now that you mention it, it's as though I new that all along. Feel like banging my head against the wall.

So that's decided now. It will be the 5600X or even 5800X. That now leaves me with the extra job of finding a decent GPU. Budget isn't an issue but I wouldn't pay today's prices, it's just not right!

 

[Eximo]

It is a bit confusing to have two standards on the same board. But it has been pretty typical. A long while where the CPUs provided PCIe 3.0 and the chipset only 2.0. Perfectly reasonable cost reduction at the time and now.

PCIe 4.0 drives aren't all they are cracked up to be. Give it a generation or two and they can get the power requirements down so they don't overheat under sustained loads (that is why they have the big heatsinks on them)

 

[TommyTwoTone66]

There is no "limitation" by being stuck at PCIe 3.0 vs a newer board with PCIe 4.0, no. Any performance impact is purely imagined, based on a future technology which hasn't been released yet and isn't planned.

Firstly, no device currently for sale actually requires 4.0 to run, every single device which supports 4.0 is also backward compatible to 3.0.

The difference is this:

PCIe 3.0 - Maximum bandwidth of 32Gbit
PCIe 4.0 - Maximum bandwidth of 64Gbit

Which, on the face of it, seems significant.

Until you realise that the fastest GPU in the world, the RTX3090, uses an absolute maximum of 18Gbit, and the fastest NVMe drives use around 24Gbit.

Graphics cards that can make use of more than 32Gbit memory bandwidth won't be around for many years, and NVMe drives which can use more than that probably a couple of years at least. By the time they are around, whatever the successor to Alder Lake is will be out and you will need yet another motherboard anyway.

So no, there is no point to PCIe 4.0 yet, it's more about being "future-proof", for a future where you will have a new motherboard anyway.

 

[mdd1963]

I did not see a GPU mentioned in the initial parts listing, which is feasible if pondering a soon-to-be-released 5600G...

Naturally, if now leaning towards a 5600X or 58000X, then a discrete GPU will then be required...

 

[Tingu]

There is no "limitation" by being stuck at PCIe 3.0 vs a newer board with PCIe 4.0, no. Any performance impact is purely imagined, based on a future technology which hasn't been released yet and isn't planned.

Firstly, no device currently for sale actually requires 4.0 to run, every single device which supports 4.0 is also backward compatible to 3.0.

The difference is this:

PCIe 3.0 - Maximum bandwidth of 32Gbit
PCIe 4.0 - Maximum bandwidth of 64Gbit

Which, on the face of it, seems significant.

Until you realise that the fastest GPU in the world, the RTX3090, uses an absolute maximum of 18Gbit, and the fastest NVMe drives use around 24Gbit.

Graphics cards that can make use of more than 32Gbit memory bandwidth won't be around for many years, and NVMe drives which can use more than that probably a couple of years at least. By the time they are around, whatever the successor to Alder Lake is will be out and you will need yet another motherboard anyway.

So no, there is no point to PCIe 4.0 yet, it's more about being "future-proof", for a future where you will have a new motherboard anyway.

Great advice thanks. Yes, I was all about future proofing. But the point you make about needing a new motherboard by the time devices are actually available, is making me rethink my build.