[Coco] Update: os9gen on 128k coco3, rs323 pack

[Gene Heskett]

On Sunday 15 February 2009, Steven Hirsch wrote:
>On Sun, 15 Feb 2009, Michael Furman wrote:
>> I tried using the rs232 pak ROM and it seems to hang occasionally.
>
>There's an obscure problem with interrupt handling that might be behind
>the hangs.  I have no personal experience with it, but it's written up in
>"Tandy's Little Wonder" (Farna Systems?).  IIRC, interrupts are not
>properly shared between the cartridge slot and the GIME with the end
>result being that SIO interrupts can be lost.  Again, just speculation
>that this is the issue!
>
There is about a 100/1 chance that is correct.  The fix is to remove three of 
the 4 pullup r's tied to each card socket pin 8, and then jumper all sockets 
pin 8's together.  This allows the IRQ to get through to the coco and be 
serviced regardless of where the slot switch is, or what slot was last 
selected by the software.

>> I'm using an MPI that has not been modified for use with a coco3.  I need
>> to order a new PAL and get this done.
>
>If it's a small beige unit, you're looking at more than a PAL replacement.
>There's a gate that needs to be added in order to prevent address aliasing
>into a region that's owned by the GIME chip on the CoCo 3.
>
>Not rocket science, but a good few hour's work.



-- 
Cheers, Gene
"There are four boxes to be used in defense of liberty:
 soap, ballot, jury, and ammo. Please use in that order."
-Ed Howdershelt (Author)
Jayne: "No offense, Doc, I think it's noble as a grape the way you 
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