X870 or X670?

[edgedemon]

I could do with some help understanding the difference in available PCIe lanes and whether I even need them?

Im only considering mini-ITX right now and I want USB4
That means X670 wise Im looking at the Asus ROG Strix X670E-I
As I understand it, this mobo has 2 Promontory chipsets that give me Gen 5 connectivity for 1 x M2, gfx card and I also get additional Gen 4 x12 and Gen 3 x8 lanes.

For the equivalent X870 mobo I lose one of the promontory chipsets, still have Gen 5 connectivity for 1 x M2, gfx card, but drop to lower additional Gen 4 x8 and Gen 3 x 4 lanes.

Practically what does this actually mean? For an ITX board does this even matter as there are so few expansion slots or will I limited if I make use of the higher speed USB connectivity available on these boards?

Im just trying to understand if I might be limiting myself with X870 or for all practical things, I don't have to worry?

 

[edgedemon]

I don't think ITX needs X670E, no.

I mean, even B650E boards can have PCI-E 5.0 graphics, 1x CPU-connected PCI-E 5.0 M.2 slot (technically 2x, but they don't do it) and 2x additional M.2 slots with no impact on GPU lanes.

I believe USB4 needs 4x PCI-E 4.0 lanes, but Intel's spec for the controller on that board is 4x PCI-E 3.0.


That depends on what they put on the the board, but it should have no meaningful impact on the rest of it.

This will be the connectivity on offer, but from what you have said I might be OK.


Rear USB (Total 10 ports)
2 x USB4 (40Gbps) port(s)(2 x USB Type-C)
5 x USB 10Gbps port(s) (4 x Type-A + 1 x USB Type-C)
3 x USB 2.0 port(s) (3 x Type-A)
Front USB (Total 3 ports)
1 x USB 10Gbps connector (supports USB Type-C)
1 x USB 5Gbps header supports 2 additional USB 5Gbps ports
* USB Type-C power delivery output: max. 5V/3A
ROG STRIX HIVE II(Total 2 ports)
2 x USB 10Gbps port ( 1 x Type-A + 1 x USB Type-C)
ROG FPS Card (Total 3 ports)
2 x USB 2.0 headers additional 3 USB 2.0 ports

I have no idea how to map that out into available PCIe lanes to see if there is any compromise. X670 offers the same but has an additional 4 x Gen 4 and 4 x Gen 3 PCIe lanes compared to X870

 

[edgedemon]

If you look at Anandtech's launch article here, they have the block diagrams for X670/X670E/B650/B650E which shows you where the USB ports come from relative to the CPU and the chipset.

Generally speaking, if there are no exclusions/sharing listed in the manual then you're usually fine. Chipset connected stuff does share one narrow uplink to the CPU, but realistically you're not going to notice.

Perfect! Thank you

I also found the following

Comparison

In summary

"the difference between an X870 and X670 motherboard can be fairly significant. An X870 chipset will have half the number of USB ports as an X670 and fewer free PCI-e lanes for additional networking, storage, or PCI-e slots."

 

[edgedemon]

I think so but the same still applies. I was waiting for the x870 release but I think I might be better off with the Strix X670E-I as plain old X870 seems gimped and is basically B650 with USB 4 as far as I can see.
I guess it will come down to price and whether I can live with the clear CMOS header being on the riser card and the hive of course.

 

[edgedemon]

With X670 not having PCI-E 5.0 support, I don't know of any X670 ITX boards. My guess is that they will still use X870E instead of X870, for technical and marketing reasons.

X870 looks like B650E to me, in that table.

Yeah it looks like B650E is being rebranded to X870, no doubt to try and command a higher price.

So I guess the big question for me is do I go for the X670E Strix ITX board or wait for the X870 version which is a slight downgrade and more like their (now unavailable) B650E offering.
On the X870 side is that it is a new platform, a lot of the Asus apps/features have been upgraded to version 2 (I don't know if they are board specific), there might be some microcode that will suit the 9950X more than the X670E mobo.
However it is a downgrade on the PCIe lanes side of things and a bit cheeky from Asus.
On the X670E side, Im buying the best available mini ITX mobo on the current platform that with a BIOS upgrade will support 9950X and will last me through to the end of AM5, but it isn't as new and shiny
It also has issues with the placement of the clear CMOS header on the riser card and BIOS flashback needing the Hive, though I think that was fixed in later BIOS. Overall these are small issues.

Unless there is a big price difference or reviews pick up on a performance increase on X870, then reading back through this post I think I have answered my question, Im better off going for the top of the current gen X670E rather than a B650E promoted to X870. Thanks OCUK - it is good to post and get help with clarifying my sometimes random thought processes.

 

[edgedemon]

I’d wager that the new X870 boards are going to be even more expensive than X670 so that’s a factor.

I can’t see it being worthwhile spending a lot of money on a motherboard if there’s a much cheaper one that’s good enough but it’s up to you and how much you need USB4.

Apparently, and this needs confirmation, but the new AMD boards are going to have more USB4 implementation but that remains to be seen.

It isn't just the USB4, X870 doesn't have the PCIe lanes that X670E has. If Im going to spend 400 on a mobo, I might as well get the best I can and at the moment, X670E beats X870 as there isn't currently a mini ITX version for X870E, only X870.
If X870 ITX comes in at 300 quid, then I will have another think but Im waiting to see pricing and reviews.

 

[edgedemon]

I've purchased a x670e recently because I'm seeing a few reports the new chipset is going to be even more expensive and it's likely AMD will stop producing x670 chips shortly

I think you are right, this is a worry, Im hoping that they stop after X870 release..

I did see a leak that X870 was around the 350 mark for the ITX, I think it was videocardz, that makes it close enough to X670E that I might as well go for X670E rather than X870 (B650E)

 

[edgedemon]

If you look at Anandtech's launch article here, they have the block diagrams for X670/X670E/B650/B650E which shows you where the USB ports come from relative to the CPU and the chipset.

Generally speaking, if there are no exclusions/sharing listed in the manual then you're usually fine. Chipset connected stuff does share one narrow uplink to the CPU, but realistically you're not going to notice.

Based on the diagram for B650, I think Im alright for PCIe lanes then.
Im going to go for X870 as the following excerpt from Anandtech states for X670

And while this configuration adds more I/O lanes (and thus more I/O bandwidth), it should be noted that all of these I/O lanes are still gated behind the PCIe 4.0 x4 connection going back to the CPU. So the amount of backhaul bandwidth available between the chipsets and the CPU is not any higher than it is on B650. The name of the game here is flexibility; AMD is not designing this platform for lots of sustained, high-speed I/O outside of the CPU-connected x16 PCIe graphics slot and M.2 slots. Rather, it’s designed to have a lot of peripherals attached that are either low bandwidth, or only periodically need high bandwidths.

in addition if AM5 is going through to 2027 and (if) there is one more gen CPU release then I have a better chance of getting X870 updated for next gen then X670 if they want to be really ***p about it

Only real worthwhile differences between X670 and X870 is more USB4 and Wifi7, Under the hood it's the same chipset.

I don't think it is, X670 is 2 x B650 chipsets as it has 2 x Prom21 chips as opposed to 1 on B650 and X870.

 

[edgedemon]

I think we're having that E versus non-E issue again there.

X670E and X870E appear to be the same. X870 is B650E. X670 is X670E without the PCI-E graphics.

I don't know why AMD made the decision to remove the E version of the B board and downgrade the X670 equivalent, seems a bit silly, but they apparently consider PCI-E 5.0 graphics to be a premium feature more than the PCI-E lanes.


That's not an issue for most users, because they're not normally exceeding the uplink bandwidth. If you run out of lanes on B650E/X670 and end up stealing the GPU lanes that is more likely to be a problem, hence if someone wants 4x M.2 slots it is prudent to get X670 or X670E (or X870E).

Quite possibly My understanding from everything I have read is that X670E has 2 Prom21 chips in serial for additional PCI-e lanes for peripherals as well as the extra lanes for the GFX. Agree X870 is B650E. Just the 2 M.2 drives so I will be OK, 1 x Gen4 and 1 x Gen5.

Just get a new case and ATX, no? Small boards are so gimped they're not worth having

I have had a full tower since 2011, now my ex gaming room is now an office for both of us, I want something tiny as I really need the space. Otherwise I completely agree. Mini ITX is small enough for me to have on the spare space on my monitor stand.