7 Mar
2011
7 Mar
'11
1:18 p.m.
Interesting. The Sirius was famous in its day for the
"wining tones" of
the variable speed disk drive, which the Commodore didn't have (in a
As I mentioned in a later message, the Commodore drives were fixed
spindle speed, variable data rate, the Sirius ones were fixed data rate,
varaible sipindle speed. Comes to muc hthe same thing in the end
later post someone says that the Commodore drives
changed the data rate
instead), so I'm surprised they're so similar.
The motor cotnrol circuitry is very different, of course. I was taling
about the GCR encoder/decoder as being the part that is very similar. I
assum,e you have schematics of both.
The other thing about the Sirius which is odd if you don't realise the
originalsm but obvious wehn you do is that it is _full_ of 6522 VIA chips
(in a 8088 system). There are 3 on the CPU board. IIRC one for system
cotnrol buncutions like brightness, contrast, etc, one for the printer
port (which is actually a GPIB port on the wrong connector and with an
odd pinput! [1]) and one for the user port (actually, I think one of the
timers in that one also generates the cound system clock). And anotehr 3
6522s on the disk cotnrolelr board, one for the data ports, one for the
motor control, and one for various other control functions.
[1] It's a 36 pin Microribbon connaotr, and it nomiallu, at least, a
Centronics port with a standard pinout. It's actually driven by 75160 and
75161 chips (I think it's those), -- GPIB buffers. The data lines end up
on 2-9 of the connectector (Centronics data lines), DAV is on pin 1
(stb/),. and so on. With the standard software it's a Centronics port,
but it would only take a little software and the right cable to link GPIB
devices here.
-tony