Re: DOS 3.3 Nibble Encoding

[borchert@i50s19.ira.uka.de (Volker Borchert)]

k_bouchard@csc32.enet.dec.com (My name is...) writes:
|> 
|> borchert@i50s19.ira.uka.de (Volker Borchert) writes...
|> >k_bouchard@csc32.enet.dec.com (My name is...) writes:
|> >|> Am I out in left field on this? All this verbage to explain something
|> >|> basic? I always thought that *any* computer boots from sector0-track0
|> >|> because [...]
|> > 
|> >Wrong. My Z80 machines boot from track $17, sector $3.
[...]
|> I guess I was thinking of older computers that had dedicated disk controllers
|> with track/sector registers and no built in ROM. I guess if a peripheral card
|> has some built-in ROM,anything's possible after a power-up.

My computers are indeed elderly. Therefore the disk controller is even
more primitive than you dared to think - it's a Z80 PIO driving control/
status lines, a Z80 CTC, a Fairchild 9401 CRC chip and about 25 TTL's.
Much of the disk r/w timing has to be done in software. But the good
thing is that the "RWTS" equivalent is in the monitor PROM (only 3K at
all!), and so is the boot loader. The $1703 is hard-coded in the "boot"
monitor command.

-- 

* "I'm a doctor, not a mechanic." Dr Leonard McCoy <mccoy@ncc1701.starfleet.fed> *
* "I'm a mechanic, not a doctor." Volker Borchert <borchert@ira.uka.de>          *