RE: CBM-900 floppy disk format/encoding

From: Hoffmann-Vetter, Martin <>
Date: Sat, 29 Oct 2011 01:37:42 +0200
Message-ID: <002501cc95ca$97e3c180$1b09a8c0@mhvnb10>

> Just besides an EPROM labeled "Z8000 Fl. Cont. S41 6-20-85"....

Can you dump the rom?

> The EPROM, MOS 6508, MOS 8723 and some other nearby discrete
> components on the mainboard seems to constitute a separate floppy
> controller just as the external CBM drives are made.

That's very interesting. So this was a modern SFD1001 without the ieee
interface? Did anyone know more about the floppy controller chip MOS 8723?

> Only I've never
> seen a 6508 in any CBM drives - usually 2x6502, 6504 and other
> 650x'es etc...

The 2040/3040/4040 use the pair 6502/6504. The later version 8050/8250/1001
use two 6502. No other CPUs are used.

But why don't use a 6508 with some ram and io? So the disk controller system
(one cpu) from the cbm floppy drives can be implementated. That's very

> I'll put up some photos some day - I just need to get a little further
> in the process.

That would by great.

What's the history from this C900? Is it a workstation or server model?



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Received on 2011-10-29 00:00:08

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