Re: Apple //c smartport compact flash adapter

[Eric Rucker <bhtooefr@gmail.com>]

On Feb 2, 1:20 pm, Patrick Schaefer <pa.schae...@web.de> wrote:
> But remember: the SD specification with its easy-to-use SPI mode goes up
> to 2GB only. SD cards with 4, 8, 16GB are SDHC, not SD!

I'm not finding anything that says that SDHC doesn't support SPI. I
believe there are protocol changes, but it's still SPI.

In any case, while SDHC support wouldn't be a bad idea, simply because
of how common SDHC cards are, it's not that relevant. Assuming that no
other drives are present (not even the internal 5.25,) you can only
have a maximum of 14 partitions on an 8-bit machine, and they'll all
either be ProDOS, Pascal, or CP/M partitions, which are limited to 32
MiB.

So, 448 MiB is the most space that a //c could theoretically even use,
and that's with unplugging the internal drive. 13 partitions, or 416
MiB, if you leave that plugged in. And, to be very safe, you also have
to assume that a second 5.25" drive is present, as well as two 3.5"
drives and a RAMdisk of some sort, so you've got 9 partitions, or 288
MiB as the safe maximum.

And, as Rob was using the CFFA partition standard, that puts an
additional constraint. The CFFA has two possible partition maps:

4 32 MiB partitions, 2 1 GiB partitions (it uses them in this order,
but if it reaches the end of the device before reaching the end of the
partitions, it will stop, and if necessary make the last partition it
was able to use smaller. Also, the 1 GiB partitions are only available
using the GS/OS driver)
8 32 MiB partitions (same rules as the 4+2)

While the CFFA partition standard is extremely simple, software is
written expecting either 4, 4+2, or 8 partitions on a CFFA-partitioned
device. Therefore, obeying that standard would be best, so now we're
at 256 MiB.

(By the way, if the 8 partition standard is used, support for both
partition maps is likely best, in case someone is sharing a SD card
between the //c and a CFFA-equipped IIGS with a SD to CF adapter. One
jumper or DIP switch, and then you prevent someone from stomping over
the first 128 MiB of their first HFS partition.)