Tuesday, December 26th 2017

AMD 400-series Chipset Surfaces on PCI-SIG, PCIe 3.0 General Purpose Confirmed

AMD's second-generation Ryzen processors, which debut some time in Q1-2018, will be accompanied by the company's new 400-series motherboard chipset, even though they are expected to work with existing socket AM4 motherboards based on 300-series chipsets (with BIOS updates). The 400-series Promontory chipset surfaced on the PCIe Integrators List of PCI-SIG, the standards governing body of the PCI bus (which also oversees PCIe specifications development).

The listing seems to confirm that 400-series chipset will feature PCI-Express gen 3.0 general purpose lanes. These are downstream PCIe lanes put out by the chipset, to run the various external onboard controllers on the motherboard, and usually wired to the x1 and x4 PCIe slots. The current 300-series chipset only features up to 8 PCIe gen 2.0 general purpose lanes, and that was seen as a drawback. AMD Ryzen socket AM4 processors put out additional gen 3.0 lanes besides the 16 lanes allocated to PEG (one x16 or two x8, physically x16 slots); and 4 lanes serving as chipset bus. These additional gen 3.0 lanes typically drive a 32 Gb/s M.2 slot. With 400-series chipset bringing gen 3.0 general purpose lanes, one can expect newer socket AM4 motherboards with more than one 32 Gb/s M.2 slot (one from the SoC, another from the chipset).
Sources: PCI-SIG Integrators List, VideoCardz
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30 Comments on AMD 400-series Chipset Surfaces on PCI-SIG, PCIe 3.0 General Purpose Confirmed

#26
Aquinus
Resident Wat-man
notbNot so long ago we had fast internal interfaces (PCI, SATA) and slow external ones (USB). It's not true anymore. Where do you think Thunderbolt 3 should be wired to? Keep in mind it may be used for external GPU or majority of PC storage (even the "operational" kind, not some seldom used backups). Notebooks drive the PC evolution and desktops will have to accept some technologies and design decisions.
It's hard to say because you don't know a lot about what's on the other end of the TB cable. It could be a display, it could be a GPU, it could be a network adapter. What you also don't know is the length of the cable or the latency introduced by the cable and the hardware it houses. Don't forget that the signal coming out of a TB port is not the same signal getting sent over the wire (or fiber) itself. That's why optical TB cables can exist, which introduces the problem of latency. Signals don't travel faster than the speed of light and assuming you actually get the speed of light (forget the time it takes to convert the signal to and from the signal from the port,) you introduce 1 nanosecond of latency for every ~0.3m of cable (assuming straight line, which twisted pairs aren't but, fiber is.) So If the cable is a 3 meter long optical cable, you've already introduced 10 nanoseconds of latency by the cable alone and will add another 10ns for every additional 3 meters on top of the constant latency introduced by the conversion circuitry.

So, TB is already a terrible choice for latency. If the PCH had the bandwidth, adding a little more probably wouldn't kill it however, you might want it connected to the CPU for the very reason that you're already dealing with a lot of latency because of how it works. So, there are trade-offs whatever way you go. I think that GPUs over TB is the exception, not the rule so, I would probably say, not the CPU if CPU PCIe lanes are at a premium. The cost of having it go through the PCH is probably not very high though because latency sensitive applications will already be suffering over TB compared to being in an actual PCIe slot.
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#27
TheLostSwede
News Editor
Seriously, too many people in this thread are getting things out of this news post that makes no sense.

Look at that, Intel's chipsets apparently only supports four PCIe slots as well if I read this like some of you do...
That's not what it says though, it says that the maximum lane width is a total of four lanes, i.e. the chipsets can ad the most provide a x4 slot, i.e. for an M.2 NVMe slot for example...

This doesn't say anything about how many lanes the chipsets provide, at all.



I think you all need to take a chill pill and read things before posting angry comments about things you don't fully understand.
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#28
Aquinus
Resident Wat-man
TheLostSwedeSeriously, too many people in this thread are getting things out of this news post that makes no sense.

Look at that, Intel's chipsets apparently only supports four PCIe slots as well if I read this like some of you do...
That's not what it says though, it says that the maximum lane width is a total of four lanes, i.e. the chipsets can ad the most provide a x4 slot, i.e. for an M.2 NVMe slot for example...

This doesn't say anything about how many lanes the chipsets provide, at all.



I think you all need to take a chill pill and read things before posting angry comments about things you don't fully understand.
No, it says that it's replacing the 300-series chipset which only has 8 PCIe 2.0 lanes and that the entire article revolves around the addition of PCIe 3.0 to the chipset. With no further information, I would expect there to be just as many PCIe lanes as in the past, just running at PCIe 3.0 instead, which means no more than two, full, 4x slots or 8 PCIe lanes (just like it's predecessor.)
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#29
notb
TheLostSwedeLook at that, Intel's chipsets apparently only supports four PCIe slots as well if I read this like some of you do...
So the recommended approach would be: stop looking at those tables, thinking about PCIe lanes and all that technical stuff.
Simple fact is: Z370 motherboards offer up to three M.2 x4 slots (or two M.2 and Thunderbolt 3). X370 variants (even put in the same segment - like AsRock Taichi) offer a single M.2 x4.
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#30
Imsochobo
notbSo the recommended approach would be: stop looking at those tables, thinking about PCIe lanes and all that technical stuff.
Simple fact is: Z370 motherboards offer up to three M.2 x4 slots (or two M.2 and Thunderbolt 3). X370 variants (even put in the same segment - like AsRock Taichi) offer a single M.2 x4.
They do, but use One 960 pro and the others cannot be used pretty much, throw in a usb3 device and half of the nvme can be used up.

Question is:
What the hell is the point ?, it offers no performance, it increases the latency and decreases performance thus it's pointless you might aswell have NVME to SATA at this point.
Intel says up to 24x pci-e through chipset or something while it's limited by 4X to the rest of the system so I wonder... what is the point of it all? sharing 4x on 2 drives is ok, but 3 drives, usb, sound, network, sata+++ then you start getting into a serious x4 bottleneck >_<

AMD's approach is easier: everything has almost dedicated bandwidth.

Not that I'd want to see two cool fancy 4X on the boards but in theory if ryzen 2 comes with PCI-E 4.0 the existing nvme and pci-e slots should be pci-e 4 on 300 series boards but not to chipset, free upgrade on older chipsets too.
Thus making gpu and other pci-e slots also pci-e 4.0 for those not through chipset.

Hopefully that is what happens :)
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