On Wed, Nov 19, 2003 at 01:30:21PM -0500, Jason McBrien wrote:
> If I'm not mistaken, Commodore DOS, or whatever it's called, lived on the
> 1541/1751/1851 disk drive itself.
Yep... and the 2040/3040/4040/8050/8250/D9060/D9090...
> The BASIC interpreter in the C64/VIC20/C128/whatever had commands that
> sent messages to the drive over the serial "Drive" port.
Or over the IEEE-488, in the case of PET and B-series machines, etc. (or
over a C-64 or VIC-20 IEEE cart as well).
> I'm not sure what processor the drive had, probably another 6502 or
> equivalent, as they used to cost as much as the Commmodore 64 itself.
In the case of the 1541, it is a 6502. In the case of some of the older
drives, a 6502 and another 6502-family processor, like a 6504 (same
features, but in a package with a reduced pin count and a smaller
accessible address bus).
There was a piece of software that made things easier, commonly called
the "DOS Wedge", but it was entirely optional. It patched the routine
in low memory (around $0070) to intercept interactive commands that
started with certain characters (like ">") and, in effect, extended
BASIC to let you do certain disk operations like directories, format
and rename commands, and check the error channel. More or less, it
was a soft-loadable version of the routines that BASIC 4 had in ROM.
But it still wasn't a DOS.
-ethan
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Received on Wed Nov 19 2003 - 17:24:43 GMT