Reply 200 of 358, by weedeewee
hyoenmadan wrote on 2021-09-18, 13:54:weedeewee wrote on 2021-09-18, 12:45:
I'd settle for anything that can do pio & dma transfers, UDMA33 is plenty, which I think an rpi with some gluelogic should be able to manage.
If with "some gluelogic" do you mean an FPGA frontend doing all the nasty bus talking work, then yes. But again, FPGA == Cost (aka, not below 90USD).
Please, read the NetPI post again... Even with the FPGA, they didn't managed to get past PIO4 in such configuration. Man, why is so difficult to accept it? Sure, the RPi can do lots of amazing things... But fast realtime IO processing isn't one of them. It is a different deal, in a way you can have a tiny JMicron with a 8042-like MCU translating from SATA to IDE. Why? Because the processing CPU raw power doesn't matter as much as the IO processing power and latency, which these things do all in specialized ASIC logic. You can throw all the raw processing powers of an ARM Cortex on the task, and still don't match JMicron's, because your IO is deficient.
What is so difficult to accept for you ? I'm just daydreaming here, throwing ideas of the top of my head.
Did the builders of the netpi know about the SMI for datatransfer? I doubt it, since it's mentioned they're using spi for that.
oh and I know you can't use it for this purpose, but the cheapest fpga on mouser is 1.24 €
and on a side note. I've got an external usb case for a sata cdrom which has an eject button which somehow uses the sata signals!? do you have any clue on that ?
edit : oh and the netpi was developed on a first gen Raspberry pi.
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