[Coco] Question about MPI behavior

[Robert Hermanek]

That was the problem, thanks so much.  I'm not familiar with the $FF7F 
control register, I'll have to look at the MPI manual for that.  Sounds like 
if I then wanted to use the registers of the rs-232 pak itself, I'd have to 
POKE myself back to slot 1.  Good to know!

Thanks

----- Original Message ----- 
From: "Robert Gault" <robert.gault at att.net>
To: "CoCoList for Color Computer Enthusiasts" <coco at maltedmedia.com>
Sent: Monday, April 16, 2012 4:46 PM
Subject: Re: [Coco] Question about MPI behavior


> Robert Hermanek wrote:
>> I had an expectation that the following would work, but it apparently 
>> doesn't and I'm curious what people think:
>>
>> The plan:  I want to be able to boot up to HDB-DOS DW3 when I power up, 
>> but I also want to access real floppies, and also be able to use the 
>> original DOS in the drive controller when I want.  So I tried this 
>> configuration:
>>
>> 1)  Removed ROM from rs-232 pak and inserted HDB-DOS in it's place.
>> 2)  Got out my MPI and upgraded it with PAL fix
>> 3)  Plugged rs-232 Pak into slot 1, and a regular unmodified floppy 
>> controller into slot 4.
>>
>> Now, at this my expectation was:
>>
>> If I have my MPI selector on 1, I'll get HDB-DOS
>> If I have my MPI selector on 4, I'll get unmodified DOS from the floppy 
>> controller.
>>
>> And that's exactly what happens.  And HDB-DOS can access drivewire images 
>> no problem, so I know it's working.  However, apparently the physical 
>> floppy drives cannot be accessed by HDB-DOS when I desire it, when the 
>> MPI selector is on 1.  My thought was that this would work:
>>
>> Boot up to HDB-DOS, then if I want to access a physical floppy hooked to 
>> the controller in slot 4, I can just use the standard commands:
>>
>> DRIVE OFF 0
>> DIR 0
>>
>> But it hangs up on the DIR command, and there is no floppy acivity.  If I 
>> boot up to regular DOS on slot 4, then the floppy works fine.  It was my 
>> understanding that all the MPI selector did was choose which ROM to 
>> enable, but otherwise any conencted devices should still be available.  I 
>> used to have HDB-DOS ROM in a floppy controller directly, and it worked 
>> fine accessing these physical drives.  So I'm surprised that when it get 
>> loaded from another MPI slot and pak, it no longer works.  Thoughts?
>>
>> -Robert Hermanek
>>
>
> It should work and a very similar setup works for me.
>
> FDC in slot4
> Roger's SDMicro Drive Pak in slot1
> A LOADM version of HDBDOS for Drivewire is on a "disk" in the SDMicro pak.
>
> MPI selector on slot 1 which starts up the Pak and CoCoNet.
> Select loading HDBDOS from a menu and HDBDOS starts.
> DRIVE OFF does select real floppies.
> DIR 0 does read disk0
>
> I use a short Basic program as part of the LOADM routine to either clear 
> or set the HDBDOS Offset values (they are typically $000000 for Drivewire) 
> and with the offset=$5A000 and a .vhd drive in DW slot0, that drive will 
> autostart AUTOEXEC.BAS.
>
> The MPI switch selects both the ROM and disk I/O. You can send a value to 
> $FF7F to split which slot has the ROM and which the FDC.
> Perhaps something in your specific ROM has not correctly set $FF7F. You 
> could try POKE &HFF7F,3  which would indicate the ROM is in slot1 and the 
> I/O device in slot4.
>
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