Sirius/Victor computer

From: Nicolas Welte (
Date: 2000-01-28 22:34:23


during the last two months I felt like living in Commodore heaven at the
University, because the building where I work is being repaired and a
lot of old stuff is turning up :-) I try to take the Commodore 8bit
stuff with me of course, but some other equipment has to go. Today I
tried to find out if these old Sirius or Victor MS-DOS computers are
worth anything, and a Web search returned Cameron's Secret Weapons page
as a result. It seems these machines were designed by Chuck Peddle after
he has left Commodore and this makes them very interesting of course. I
knew before that the disk drives of the machines use variable speed
technology similar to the early Macs and that some sort of GCR coding
was used. But I also found a dump of the Victor's GCR ROM on the net
today, and compared it to the GCR ROM of 4040 and 8050 drives: they are
extremely similar, the address map is a little different and in one part
of the ROM one bit is permanently set, but otherwise the contents are
just the same. It almost looks like this ROM was "borrowed" from CBM
machines :-) I guess I will have to have a close look at the hardware of
these computers, if there are any other similarities to CBM 8bit

Did CBM have a patent for the GCR technology or maybe the speed zone
implementation with the variable bit clock? Why did others always use
variable spindle speeds instead? It's probably easier to design the data
recovery circuit for a fixed clock, but a variable speed drive also
isn't that trivial... 

Also, it's a while since I tried to understand what the GCR ROM actually
does in a 8250: I think it looked like being able to convert a whole
byte in one direction, but only half a byte into the other one. Can
someone please confirm if this is correct or not?


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