[Coco] Disto SC (NOT) needed

[Joel Ewy]

Darren A wrote:
> On 11/15/08, Joel Ewy wrote:
>   
>> Darren A wrote:
>>     
>>> Roger. The problem is almost certainly a blown HALT line inside the
>>> CPU. I've had two such processors which behaved normally except when
>>> disk I/O was performed. In both cases, tests revealed a blown HALT
>>> line. The 6809 seems to be plagued by this problem. Replacing the CPU
>>> will most likely fix the CoCos so they can once again use disks.
>>>
>>> Darren
>>>
>>>
>>>       
>> Hmm.  Could you use a Super Controller II with a CPU that has no HALT
>> line?  :)  (Probably not easily in practice, since the SCII runs in halt
>> mode until the OS-9-only no-halt driver is loaded, and how will you boot
>> OS-9?  Can you boot OS-9 over Drivewire?  Or you could burn OS-9 into
>> EPROM.  I guess you could also use it in a cassette only system...)
>>
>> JCE
>>     
>
>
> Even with a standard Tandy controller, it is possible to burn a new
> Disk Basic EPROM with a modified version of the DSKCON routine which
> does not enable HALT (but still requires that interrupts be masked).
> The same could be done for the rb1773 driver for OS-9 and NitrOS-9.
> This would allow a CoCo whose CPU has a blown HALT line to be able to
> run most disk-based software. Programs which implement their own disk
> I/O functions would still be inoperable.
>
> Darren
>
>   
So it would just poll the FDC register in a busy loop until a sector was
ready?

JCE
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