On the bottom of the SBC is a M.2 M key 22x80mm slot. A NVMe SSD any other fitting PCIe peripheral would fit here. How many PCIe lanes does it get?
On the top of the SBC is a M.2 E key, that one is 22x42mm is it? How many PCIe lanes does it get?
Finally do any more PCIe lanes go to any other chips on the SBC?
I would hope it’s 2x lanes to the lower M.2 + 2x lanes to the upper M.2. If I understood it right, the USB3 controller is built-in in the SoC so the USB3 consumes no PCIe lanes.
Oh wait a bit, reading the main Rock5 thread, I see a mentioning that there are more Rock5 variants and that one or both, use the “RK3588S” which is a limited RK3588 variant which only has 2x one PCIe v2 in total, is it?
Please clarify which Rock5 variants exist, and do they use RK3588S or RK3588?
(Cautionary note: There is also a “Rock5 Compute Module” and its specs are here https://wiki.radxa.com/Rock5/CM5 . That one is different altogether from the Rock5 SBC. Note that one is pin compatible with the Raspberry 4 Compute Module, and indeed it offers 2x PCIe v2 lanes.)
Oh and then, if the lower M.2 is indeed 4x PCIe v3 lanes, in this situation:
Is it possible to bifurcate that M.2 slot into two separate M.2 slots that each get 2x PCIe v3 lanes only, or would a separate PCIe switch chip be needed to accomplish that?
@jack
It is still true that big GPU cards don’t work ?
And is it possible to ask RockChip if they can fix it or if they can fix it in next silicon release?
I bought this https://www.youtube.com/watch?v=EV_kIwmgVMM
And I can connect big GPU over M.2 and I don’t see any bottleneck on CPU side
But I can use it for lots of fun stuff
There’s either PCIe Gen2 x1 or SATA in this M.2 key E slot so such a ‘module’ can not be a mechanical converter but needs to be one of those:
a PCIe switch that can turn one PCIe lane into multiple (sharing bandwidth, higher latency)
a PCIe controller e.g. providing additional SATA ports (ASM1061 for example to name the cheapest possible)
a SATA port multiplier like JMB575 that could turn the single SATA lane into 5 upstream SATA ports (I forgot whether we have already data if Rockchip’s recent SoCs support SATA PM or not and whether FIS-based switching or CBS but at least the RK3588 TRM states ‘Port Multiplier with FIS-based switching’ so this should be fine and with the SATA converter and a JMB575 we should be able to attach 5 pieces of spinning rust or SSDs to Rock 5B)
But due to space constraints none of this works in the M.2 2230 form factor so without an extender cable you’re lost.
is it also possible through combophy to enable sata through the usb3 port ? that way you can still have a option for wifi and storage through the pcie lanes .
would be nice when a vendor replace the hdmi board in a portable monitor with a rk3588 would be a nice streamer setup
It would be really great if you could ASAP purchase a JMB575 SATA port multiplier like this one and test with 2 SATA devices whether they can be seen or not. If you do so please provide dmesg output here so we can see whether FIS-based switching or CBS happens.
If you was asking me: no, thank you. I lack the M.2 SATA converter and those boards look like JMB321 which IIRC doesn’t support FIS-based switching so we could not check RK3588’s capabilities.
Asides that why not let the manufacturer do this since they’ve tested already with SATA for sure and all they lack is such a JMB575 board for a few bucks
