4 ms·

I find this fascinating, and I have a few follow-up ideas. How many PCIe lanes are on this connector? Is this a full 16x slot? I assume since it has a very lim

I find this fascinating, and I have a few follow-up ideas. How many PCIe lanes are on this connector? Is this a full 16x slot? I assume since it has a very limited amount of PINs I'd assume it's just a 1x. The next obvious step is hooking up this to a PLX chip. Duplicating the number of lanes available even if there's no additional bandwidth could really open up doors.

philcrump 6y ago
From the article it's 'just' a 1x PCI-E 2.0 lane (theoretical 5Gbps throughput). This is all the VL805 expects so all that's broken out to it's pads and 'easily' accessible.
LeonM 6y ago
It is 1x, obviously. But I highly doubt that the PCIe bus is going to be the bottleneck here ;-) I guess it would be possible to design an ATX size motherboard with a RPi4 compute module slot (once CM4 becomes available). The PCIe bus would allow all sorts of peripherals. Don't expect any performance though.
- anon73044 6y ago
  Have you seen https://turingpi.com https://turingpi.com ? I can't imagine an ATX/ITX/STX compatible breakout board for everything on the Pi 4 would be an impossible task.
  - LeonM 6y ago
    Well, yes, something like that, but not in a cluster form, but just a single CM4 on a mini-itx form factor board, with PCIe slots, USB ports, ethernet, etc. You could build a fully blown Linux desktop peripheral wise, just don't expect desktop performance.
tcas 6y ago
It's 1 lane, but a 16x connector to allow plugging in any device. PCIe devices can be downgraded into a lower number of lanes. Many motherboard 16x connectors aren't even a full 16x.
q3k 6y ago
> The next obvious step is hooking up this to a PLX chip. Duplicating the number of lanes available even if there's no additional bandwidth could really open up doors. I did this with an external PCIe 'splitter'/switch board: https://twitter.com/q3k/status/1225560443927891971 https://twitter.com/q3k/status/1225560443927891971 It worked, kinda. After a kernel rebuild with the drivers I wanted and dtb bumps to allow for more PCIe MEMBAR space i was able to get multiple devices (IIRC 10GbE and SATA controller) to work simulataneously, just very slowly.
- floatboth 6y ago
  > bumps to allow for more PCIe MEMBAR space huh! huh! can you have enough BAR space for an AMD GPU to run? Rockchip RK3399 is infamous for having too little for GPUs..

philcrump 6y ago

From the article it's 'just' a 1x PCI-E 2.0 lane (theoretical 5Gbps throughput). This is all the VL805 expects so all that's broken out to it's pads and 'easily' accessible.

LeonM 6y ago

It is 1x, obviously. But I highly doubt that the PCIe bus is going to be the bottleneck here ;-) I guess it would be possible to design an ATX size motherboard with a RPi4 compute module slot (once CM4 becomes available). The PCIe bus would allow all sorts of peripherals. Don't expect any performance though.

anon73044 6y ago
Have you seen https://turingpi.com https://turingpi.com ? I can't imagine an ATX/ITX/STX compatible breakout board for everything on the Pi 4 would be an impossible task.
- LeonM 6y ago
  Well, yes, something like that, but not in a cluster form, but just a single CM4 on a mini-itx form factor board, with PCIe slots, USB ports, ethernet, etc. You could build a fully blown Linux desktop peripheral wise, just don't expect desktop performance.

tcas 6y ago

It's 1 lane, but a 16x connector to allow plugging in any device. PCIe devices can be downgraded into a lower number of lanes. Many motherboard 16x connectors aren't even a full 16x.

q3k 6y ago

> The next obvious step is hooking up this to a PLX chip. Duplicating the number of lanes available even if there's no additional bandwidth could really open up doors. I did this with an external PCIe 'splitter'/switch board: https://twitter.com/q3k/status/1225560443927891971 https://twitter.com/q3k/status/1225560443927891971 It worked, kinda. After a kernel rebuild with the drivers I wanted and dtb bumps to allow for more PCIe MEMBAR space i was able to get multiple devices (IIRC 10GbE and SATA controller) to work simulataneously, just very slowly.

floatboth 6y ago
> bumps to allow for more PCIe MEMBAR space huh! huh! can you have enough BAR space for an AMD GPU to run? Rockchip RK3399 is infamous for having too little for GPUs..