AMD Zen 4 & Socket AM5 Explained: PCIe Lanes, Chipsets, Connectivity

[Wirko]

But there likely aren't going to be many mATX/ITX X670/X670E boards, which is a slap in the face to the SFF crowd who want to build high-end systems in small spaces.

Not very likely but not impossible, either: both dies of the X670 on a single package.

@TheLostSwede : any possibility of an "A620" chip-less set? Already answered

 

[Metroid]

So the only board to buy then is X670E because anything else is "lacking" and if AM5 lasts as much as AM4 then even if you buy a high end board is a good investment.

 

[Xajel]

I think AMD made a mistake with only providing 28 PCIE lanes on AM5. I really think USB4 will become a full standard within the lifespan of this platform. Maybe Zen 5 will end up replacing the USB3 with USB4...

32 PCIE lanes would have been more forward looking at the start of a 5+ year platform.

It will, but not in the chipset but the platform. Maybe AMD will do it later with X770/X870 when it sees that is viable financially and technically, even thought I would love to add it at least to the X670E only.

 

[GeorgeMan]

So the only board to buy then is X670E because anything else is "lacking" and if AM5 lasts as much as AM4 then even if you buy a high end board is a good investment.

Did they make any statements this time? I don't think so...

 

[Xajel]

So the only board to buy then is X670E because anything else is "lacking" and if AM5 lasts as much as AM4 then even if you buy a high end board is a good investment.

It should last the same or even more, considering AM4 was already late to the market (considering when DDR4 was launched before). But they will release updated chipsets with every new CPU generation.

 

[TheLostSwede]

It will, but not in the chipset but the platform. Maybe AMD will do it later with X770/X870 when it sees that is viable financially and technically, even thought I would love to add it at least to the X670E only.

There will be add-in cards. Not sure if the feature parity will be 100% though.

 

[TheinsanegamerN]

CPU

So I was right - no native USB4 from this platform. That is seriously disappointing considering Tiger and Alder Lake has it baked in. The biggest benefit of USB4 (apart from bandwidth) is that there's none of the "does this USB-C port support DP alt mode" nonsense, because all USB4 ports have to support DP alt mode.

... and there we have it, up to four USB 3.2 gen 2 ports, but DP alt mode is optional and one of them arbitrarily doesn't support DP alt mode at all. WHHHHHYYYYYY? It also seems like these ports cannot be bonded to 3.2 gen 2x2, again why?

Are the up-to-4 display outputs muxed with the up-to-3 USB 3.2 gen 2s with DP alt mode? In other word, could you have 7 displays being driven by the CPU, or is 4 the hard limit?

Chipset

I like the option to have zero SATA ports in favour of an extra NVMe drive, even if it's only PCIe 3.0.

The daisy-chained chipsets are a terrible kludge that will be a nightmare in terms of latency for devices hanging off the most downstream one. Also, what happens if one of the chipsets fails? Does the other continue to work and the board behaves like a B650? Or is it just a dead board?

Why can only the first two 3.2 gen 2 ports be bonded to 3.2 gen 2x2?

Platform overall

I honestly don't understand why AMD is launching a platform that is not natively USB4-capable... if I was wearing my conspiracy theorist hat I'd say it's to allow ASMedia to sell USB4 chips separately and thus make more money. Considering Intel has had platform-native USB4 since Tiger Lake in 2020, this makes the AM5 platform look dated before it's even launched. The chipsets' low PCIe lane count (not bandwidth) compared to ADL, is a further concern.

As such, AM5 is of no interest to me right now. I was already planning to stay on AM4 until Zen 4's successor arrived with all the bugs fixed, but native USB4 was the variable that had the potential to sway me... no native USB4, no reason to upgrade.

I'm sticking with my 5900x likely until at least 2030. CPUs just dont age much anymore.

But there likely aren't going to be many mATX/ITX X670/X670E boards, which is a slap in the face to the SFF crowd who want to build high-end systems in small spaces.

Oh yes, you need those 3 dedicated PCIe interfaces and all the slot connectivity x670 provides on a board with 1 PCIe slot

There will be add-in cards. Not sure if the feature parity will be 100% though.

Will there be? Thunderbolt had add in cards however they required thunderbolt to be built into the board to function.

 

[Nanochip]

Will x670 solutions implement JHL8440 Goshen Ridge instead of Maple Ridge JHL8540?

I thought Goshen Ridge was for docks (all the new TB4 docks have goshen ridge inside) and Maple Ridge was for hosts (z690 motherboards with TB4 have Maple Ridge).

Typo or is AMD implementing something cool ?

 

[SRB151]

There will be none. AMD will have a B650E chipset for those kind of platforms, with full PCIe 5.0 support, but that's not official as yet.


Not directly, but they said a long time, whatever that means.

Yeah, isn't that the same thing they said about TRX40? While AM4 was exceptional, I'd be looking this as a goal rather than counting on it.

 

[trsttte]

I'm sticking with my 5900x likely until at least 2030. CPUs just dont age much anymore.

What? CPUs are aging more than ever now that Intel and AMD feel like competing again for a change and ARM is threathning to steal their lunch. Absolutely keep whatever works for as long as possible but CPUs are definetely aging.

Yeah, isn't that the same thing they said about TRX40? While AM4 was exceptional, I'd be looking this as a goal rather than counting on it.

That's a very good point but I believe general consumer market would be loud enough that they wouldn't risk it.

What I could see coming is AMD being a lot more careful with what they promise to not repeat what happen when they launched zen3 (at first they wanted to support only x570/b550 and were quickly "forced" to support b450/x470 as well, and through market competition now even b350/x370 is supported as was always promised). But then again, companies are always repeating the same mistakes over and over again so who knows

 

[R0H1T]

So the only board to buy then is X670E because anything else is "lacking" and if AM5 lasts as much as AM4 then even if you buy a high end board is a good investment.

Or wait for the platform to mature a bit & buy x7xx chipset based boards next year?

What? CPUs are aging more than ever now that Intel and AMD feel like competing again for a change and ARM is threathning to steal their lunch

Yes & no, like always depends largely on what you do with them. Grandma & Pops browsing web at home can do it on an M1 based tablet easily till at least 2030

 

[Metroid]

Or wait for the platform to mature a bit & buy x7xx chipset based boards next year?

It could be, I'm not planning to sell my 5900x and upgrade just yet. I think waiting one more year would be the best thing to do now, ddr5 still not as good and still very expensive, actually anything that is pcie5 will be very expensive this year.

 

[R0H1T]

Yes with the x570 here no plans to switch to anything newer just yet. Simply not worth it for me!

 

[TheLostSwede]

Will x670 solutions implement JHL8440 Goshen Ridge instead of Maple Ridge JHL8540?

I thought Goshen Ridge was for docks (all the new TB4 docks have goshen ridge inside) and Maple Ridge was for hosts (z690 motherboards with TB4 have Maple Ridge).

Typo or is AMD implementing something cool ?

You're right, my bad, but it seems like Goshen Ridge is the only USB4 certified part, which makes it a bit strange to use Maple Ridge.
I've updated the story regardless.

 

[mechtech]

Seen title and only thing that came to mind was


The foot bone’s connected to the leg bone.
The leg bone’s connected to the knee bone.
The knee bone’s connected to the thigh bone.
…….

edit. Can I get a pci slot to use my old school sound card??

 

[Daven]

So the only board to buy then is X670E because anything else is "lacking" and if AM5 lasts as much as AM4 then even if you buy a high end board is a good investment.

I guess you can say the same thing about any CPU or GPU that isn’t the flagship CPU or GPU. SKUs are created by disabling parts or fabbing a cutdown version of the flagship. Not everyone can afford the full flagship SKU like you. Plus I don’t want manufacturers to throw away 90% of chips made just to avoid “lacking” part of the whole as long as the chips function at some capacity.

 

[ppn]

Could have moved all the 4/5.0 links and USB4.0 to the cpu, and leave only legacy SATA/USB2.0 to the chipset with capability to completely turn it off, or choose not solder it and have a chipletless motherboard. Have to wait for intel meteor lake to see if they make the step first.

 

[TheLostSwede]

I guess you can say the same thing about any CPU or GPU that isn’t the flagship CPU or GPU. SKUs are created by disabling parts or fabbing a cutdown version of the flagship. Not everyone can afford the full flagship SKU like you. Plus I don’t want manufacturers to throw away 90% of chips made just to avoid “lacking” part of the whole as long as the chips function at some capacity.

This time it's a bit different though, as PCIe 5.0 requires eight layer PCBs, whereas PCIe 4.0 can be done with six layer PCBs, so there's a fair cost difference there too, not taking into considering the potentially more expensive parts that are needed for things like the x16 slot and what not.

Could have moved all the 4/5.0 links and USB4.0 to the cpu, and leave only legacy SATA/USB2.0 to the chipset with capability to completely turn it off, or choose not solder it and have a chipletless motherboard. Have to wait for intel meteor lake to see if they make the step first.

That would make the I/O die massive and hard to cool, so that's not a great idea.
I very much doubt this will ever be the case for a full-size ATX motherboard, although AMD's A300/X300 boards were pretty much this, but none of them were bigger than mATX.

 

[ppn]

X670E is actually a very tiny chip. and unlike X570 that reused the same chip as the CPU IO. this one is not carrying a disabled cache and memory controller. What node is it build on 6nm or 12. this is probably no more than 15 watts for the duo.

 

[TheLostSwede]

X670E is actually a very tiny chip. and unlike X570 that reused the same chip as the CPU IO. this one is not carrying a disabled cache and memory controller. What node is it build on 6nm or 12. this is probably no more than 15 watts for the duo.

Not sure about the node, but each chip is said to be around 7W.
See https://www.angstronomics.com/p/site-launch-exclusive-all-the-juicy

 

[trsttte]

What node is it build on 6nm or 12

TSMC N6

 

[TheLostSwede]

TSMC N6

That was it, totally slipped my mind.

 

[LuxZg]

First of all - thanks for detailed write-up and pictures. This was info I've been looking for last several days.

And to some others, IMHO, you're stressing too much.

If I'm not mistaken this could be possible as B650 "E" ITX board:

HDMI+DP
1x x16 PCIe 5.0 (for GPU)
1x M.2 via x4 PCIe 5.0 (from CPU)
1x USB 2.0 (from CPU)
3x USB 3.2 Gen 2 with DP mode (from CPU)
1x USB 3.2 Gen 2 (from CPU)
2x USB 4 (from CPU via x4 PCIe 5.0)
2x SATA (from B650)
1x M.2 via x4 PCIe 4.0 (from B650)
1x 2.5 GbE (via PCIe 3.0 from B650)
1x WiFi (via PCIe 3.0 from B650)
6x USB 2.0 (from B650)
4x USB 3.2 Gen 2 (from B650)
1x USB 3.2 2x2 type C (from B650)

Does that sound like low end ITX board? That's what CPU with single chipset can give you. And all can be used at once (as in, nothing will be blocked if you plug in something else). Full PCIe x16 5.0, two M.2 drives, 2 SATA drives, 18 USB ports, Ethernet, WiFi, and up to 4 displays. (That's just example, I'm sure there will also be something like "home server" ITX boards with 2 network ports and 8 SATA ports instead USB 4 and WiFi such)

Now to expand on that, a full ATX X670E board (2 chipsets) can do something like:

HDMI+DP
1x x16 PCIe 5.0 (for GPU, or 2x x8)
1x M.2 via x4 PCIe 5.0 (from CPU)
1x USB 2.0 (from CPU)
3x USB 3.2 Gen 2 with DP mode (from CPU)
1x USB 3.2 Gen 2 (from CPU)
2x USB 4 (from CPU via x4 PCIe 5.0)
6x SATA (from chipsets)
2x M.2 via x4 PCIe 4.0 (from chipsets)
1x 2.5 GbE (via PCIe 3.0 from chipsets)
1x WiFi (or x1 PCIe 3.0, from chipsets)
1x x4 PCIe 4.0 (from chipsets)
12x USB 2.0 (from chipsets)
8x USB 3.2 Gen 2 (from chipsets)
2x USB 3.2 2x2 type C (from chipsets)

That's again a crazy total, like full PCIe 5.0 x16 slot (or two x8), x4 PCIe slot (or a few x1 slots), three M.2 slots (!), Ethernet+WiFi (or dual LAN), 6 SATA and up to 29 (?!) USB ports, and again no small print like "using M.2 disables 4 SATA". (And again that's just example)

I could live with that ITX "B650E" board actually, I have been thinking past several days, and I can't remember when I used anything in PCIe slot except GPU (ages ago a satellite card), always juggled 5-6 SATA drives but I can do with 2 M.2 + 2 SATA with current capacities, my days of needing 2nd LAN are gone, and WiFi can be a backup interface, and everything else can just go to USB, specially with USB4. I honestly think I can move away from ATX and E-ATX boards with this generation, and move from tower to SFF PC.

IDK, to each their own, choosing MBO is always a personal choice for tech enthusiasts, but I see no negatives with this AMD setup. Those few people that will somehow see it as flawed can always go for something like HEDT / workstation PC, be it Threadripper or Xeon or whatever.

P.S. And I loved that "no chipset" idea, I'm sure OEMs would be all over it with SFF office PCs and the like. Are we sure it's not an option? Did anyone actually say so (from AMD or MBO makers)?

Edit: typos if there's more pls excuse me

 

[Flaky]

Why would it be my assumption?
I've obviously verified this.
In fact, we're not the first publication to cover the chipset layout, we just did in a slightly different way, as the site linked to below, made some slightly flawed assumptions based on expected board layouts, which won't always be the case.

Not necessairly your assumption - might be an assumption of your sources.

With singular B650 having enough I/O to exceed capabilities of chipset link, it just seems weird to cram almost double the I/O through that already congested link. Intel went for DMI 4.0 x8 on H670/Z690 for a reason.

Parallel connection looks like a more versatile option, and there doesn't seem to be any technical reason not to choose that topology (or leave both options open for board designers).
I hope you understand my skepticism now

 

[TheLostSwede]

P.S. And I loved that "no chipset" idea, I'm sure OEMs would be all over it with SFF office PCs and the like. Are we sure it's not an option? Did anyone actually say so (from AMD or MBO makers)?

Nothing has been mentioned about it at this point in time. It would be the replacement for A300/X300 which were a CPU and a Super I/O chip and no chipset.

With singular B650 having enough I/O to exceed capabilities of chipset link, it just seems weird to cram almost double the I/O through that already congested link. Intel went for DMI 4.0 x8 on H670/Z690 for a reason.

I agree, but I was actually at the show floor of Computex, handled boards and talked to people. ASMedia doesn't seem to be ready for PCIe 5.0 and I also asked why it wasn't a chipset per CPU interface, but was told that AMD had decided to go for daisy chaining.

Parallel connection looks like a more versatile option, and there doesn't seem to be any technical reason not to choose that topology (or leave both options open for board designers).
I hope you understand my skepticism now

I guess it's not impossible we'll see boards doing that, but you'd trade four PCIe 5.0 lanes for four PCIe 4.0 lanes, which I'm not sure the board makers want to do, since higher is better, right?
In all fairness, none of this information comes directly from AMD as mentioned, so it's possible things will changed, but as you saw, there's at least one other site, who also posted several days before us, that is saying the same thing about the chipset being daisy chained. They made some flawed assumptions though, as they followed a board design, when in reality there's more flexibility than they display in their layout. Hence the somewhat awkward diagrams here, following Intel's HSIO layout to a degree, as it makes it easier to explain muxed interfaces.