[Coco] [Color Computer] Multi-Pak Question

[Robert Gault]

Roger Taylor wrote:
> At 04:04 PM 1/30/2009, you wrote:
>> On Fri, 30 Jan 2009, seanrussoct08 wrote:
>>
>>> I have a quick question.  I have a multi-pak 26-3124 that i bought off
>>> of Ebay a few years ago and haven't used it much.
>>>
>>> I had a friend several years ago tell me that he thought you could use
>>> one of these multi-paks to access more than one device at a time, but
>>> i didn't think you could.  Could someone settle this for me? and if
>>> yes, how do you?
>>
>> Well, to be precise the computer will only ever access one device at a 
>> time.  But, what I believe you're asking is whether you can have more 
>> than one cartridge plugged in and have the software get to the one 
>> that's appropriate :-).  The answer would be "yes", at least for 
>> OS-9.  For example, I have a Tandy floppy controller in slot 4, an 
>> HDisk IDE controller in slot 3 and a Burke&Burke MFM hard disk 
>> interface in slot 2. The computer is booted with the switch on slot 4 
>> for the floppy and start from there.  Once OS-9 (actually, NitrOS9) is 
>> up, any or all of them can be gotten to.
> 
> Now what if you switched the MPI to the slot you had a ROM Pak in 
> containing a disk operating system, but the floppy controller is in 
> another slot.  Would the disk operating system be able to use the 
> controller as usual.
> 
> 
> 

You should be able to have two "halt" controllers in an MPI with 
different ROMs and use the hardware from one and the software from the 
other. You won't be able to have one "non-halt" and the other "halt" as 
the code won't match. Two "non-halt" controllers, using the same 
hardware, also ought to work.

I don't know of any Disk Basic ROMs that do anything to the MPI slot. 
OS-9 is a different animal however. Some poorly written code may assume 
the default MPI slot is 3 and return the $FF7F value to $33 after 
servicing a call. Correctly written code will read the $FF7F value, save 
it, and restore it on Exit.