> On Aug 28, 2020, at 12:15 PM, David Bridgham via cctalk
> <cctalk@classiccmp.org> wrote:
>
>
>> in an online search - the CFADPTHD seems like it's close to what I'd want,
>> except it's Compact Flash; I'd have preferred SD but I guess converting
>> their interface to IDE is more work.
>
>
> Yeah, I think Compact Flash actually uses the IDE protocol just with a
> different form-factor while SD cards are their own thing so a conversion
> from SD to IDE is a whole lot more work.
Correct. CF cards talk to a SATA controller, you just have to adjust the
pinout.
SD is a packet based storage device on a serial interconnect, minimally one
lane wide but it can also be four lanes (and that's typically how you use it).
Apparently it starts out in a SPI compatible mode, interesting. Also, SD
requires a rather complex handshake at power up to get to the point where you
can do I/O.
One oddity I remember from a decade ago is that it has a high speed mode where
the clock speed is doubled. That's not strange. What's strange is that when
you do this, the device switches from clocking data on the rising edge to
clocking on the falling edge, or the other way around, I don't remember which.
Fortunately I wasn't the hardware designer who had to cope with all that
strangeness.
paul
