4 ms·

These kind of high speed interfaces aren't just something that one just bitbangs on some microcontroller. I think even the first step, ie. finding a RISC-V chi

by dezgeg 3y ago

These kind of high speed interfaces aren't just something that one just bitbangs on some microcontroller. I think even the first step, ie. finding a RISC-V chip that has capability of acting as a PCIe device at all will be a challenge. "Inexpensive" for sure not.

AnthonyMouse 3y ago
There are RISC-V chips with PCIe controllers on them. I'm not sure if you can use the hardware designed to act as a host to act as a device, but it wouldn't surprise me. In any case I would find it hard to believe that the hardware that can act as a device would cost significantly more. You can get a whole NVMe SSD for $15: https://www.newegg.com/silicon-power-128gb-p34a60/p/N82E16820301475?Item=N82E16820301475 https://www.newegg.com/silicon-power-128gb-p34a60/p/N82E1682... The hardware required to do this can't be that expensive.
- dezgeg 3y ago
  > I'm not sure if you can use the hardware designed to act as a host to act as a device, but it wouldn't surprise me. I don't how it is for PCIe, but for example USB is very asymmetric and host controllers generally cannot as devices. There do exist dual-mode IP cores (e.g. for mobile SoCs) > In any case I would find it hard to believe that the hardware that can act as a device would cost significantly more. Indeed the area/cost difference between host-only and dual mode controller may be small. But in a general purpose chip there will be dozens of other competiting features in all the other subsystems besides PCIe. Each of those small features would increase the chip cost, so they won't be added without a cost-benefit calculation. So it can still be that while PCIe device support would be cheap to add, it could still be considered too low bang-for-buck to be worth including. Or that there may be such chips supporting PCIe device mode, but they then also would include things like video encoding/decoding, HDMI, ethernet, etc. and thus be an expensive chip. > The hardware required to do this can't be that expensive. With a custom ASIC (the linked one seems to have Phison E12) that includes only the minimal needed hardware, yes.

by dezgeg 3y ago

AnthonyMouse 3y ago

There are RISC-V chips with PCIe controllers on them. I'm not sure if you can use the hardware designed to act as a host to act as a device, but it wouldn't surprise me. In any case I would find it hard to believe that the hardware that can act as a device would cost significantly more. You can get a whole NVMe SSD for $15: https://www.newegg.com/silicon-power-128gb-p34a60/p/N82E16820301475?Item=N82E16820301475 https://www.newegg.com/silicon-power-128gb-p34a60/p/N82E1682... The hardware required to do this can't be that expensive.

dezgeg 3y ago
> I'm not sure if you can use the hardware designed to act as a host to act as a device, but it wouldn't surprise me. I don't how it is for PCIe, but for example USB is very asymmetric and host controllers generally cannot as devices. There do exist dual-mode IP cores (e.g. for mobile SoCs) > In any case I would find it hard to believe that the hardware that can act as a device would cost significantly more. Indeed the area/cost difference between host-only and dual mode controller may be small. But in a general purpose chip there will be dozens of other competiting features in all the other subsystems besides PCIe. Each of those small features would increase the chip cost, so they won't be added without a cost-benefit calculation. So it can still be that while PCIe device support would be cheap to add, it could still be considered too low bang-for-buck to be worth including. Or that there may be such chips supporting PCIe device mode, but they then also would include things like video encoding/decoding, HDMI, ethernet, etc. and thus be an expensive chip. > The hardware required to do this can't be that expensive. With a custom ASIC (the linked one seems to have Phison E12) that includes only the minimal needed hardware, yes.