Other disk and drive types (Was: Hard-sector discs -- how many
ard at p850ug1.demon.co.uk
Fri Nov 20 16:54:39 CST 2009
> Some formats, such as Intertec Superbrain had the data bits inverted
> relative to the header bits
IIRC Western Digial made disk controller chips with normal and inverted
data buses (that was, IIRC, the difference between a 1791 nad a 1793, for
example). And Intertec (?) used an inverted-bus one without an external
inverting bus buffer....
> Some, such as TRS80, got weird with their Data Address Marks
Only on the directory cylinder of Model 1 TRS-DOS and clones AFAIK. When
they went to double density, the had to sue standard DAMs since that's
all the 179x chips could do. ANd IIRC LDOS used standard DAMs even on
Model 1 single-density systems.
> . . . and then, there are some obscure ones, and even some unusual ones.
Soeheter I have an Epson drive unit. It looks a it like the well-knwon
TF20, but it isn't. It's something like a BM5. The host interface is a
custom parallel one (possibly to a card that pluged into a QX10 or
something). The internal controller board contains a Z80A and a _hard
disk_ controller chip, the interface to the 5.25" drive is a 34 wasy and
a 20 way ribbon cable. Yes, it's ST412 or similar. I have no idea what
sort of floppies it uses.
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