1 Jun
2000
1 Jun
'00
9:32 a.m.
I wrote:
No, the trick (as used in SOS, and in the Lisa I/O
card ROM) is to
do 1:1 interleave *without8 a track buffer. They directly denibblize
as they're reading the bits from the disk.
Sellam Ismail <foo(a)siconic.com> wrote:
I didn't think the ][ was fast enough to do that?
That's why I called it a "trick".
After all, everyone knows that a 1 MHz 6502 isn't fast enough to do disk
control in software at all! :-) Woz's design is a classic example of
"thinking outside the box". IIRC, he was quoted somewhere as saying
that he didn't previously have any knowledge of the design of disk
controllers, so he just designed what he thought would be necessary.
Once the Intel 8271, WD 1771, and similar FDC chips became available,
any idiot could "design a disk controller". But if you compare Woz's
design with other pre-FDC-chip designs, Woz's has 1/10 as many chips
as some of them.