Re: CBM900 hard disk timeout

From: Michał Pleban <>
Date: Sun, 24 Aug 2014 21:39:07 +0200
Message-ID: <>

Michał Pleban wrote:

> The disassembly claims that the controller supports commands: 01, 05,
> 06, 08, 0A, 0B, 0C, 0D, 15, 16. I am struggling too much with the 8048
> assembly to verify it, but let's suppose it's true.

> The BIOS disassembly shows the following commands are used:
> 02 - Restore Drive (?)
> 04 - Format
> 08 - Read
> 0B - Seek
> 0C - Init Drive (?)
> The floppy controller ROM disassembly shows that it supports, among
> others, commands 04, 08 and 0A which would make sense taking into
> account the above BIOS uses (0A is supposed to mean "write").

I have checked it some more and it turns out these are simply SASI
commands. So the floppy controller uses the command 04 which means
"format disk", which makes perfect sense. The hard disk controller does
not support this command, but it does support command 06 which means
"format track". It might be theoretically possible to hack some Z8000
code to send this command to the controller to see what happens.


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Received on 2014-08-24 20:00:32

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