[Coco] Geranium Diode Upgrade

[Gene Heskett]

On Thursday 10 July 2008, Chuck Youse wrote:
>On Thu, 2008-07-10 at 14:03 -0700, Mike 0rtloff wrote:
>> The ACIAPAK driver requires this interrupt signal
>> to operate properly, although the MODPAK driver
>> does not. The signal in the CoC03 is routed
>> througi1 the GIME chip, which every so often does
>> not pass it to the CPU.
>
>Am I reading this right when I infer that the GIME has some sort of bug
>w/r/t its interrupt 'controller'?  That would be a rather nasty flaw ..

That actually turned out to be a miss read of the gime specs as they weren't 
very clear, and the gime wasn't always being re-initialized correctly after an 
IRQ was serviced.  The fix was incorporated in all the edition 9 clock modules, 
and has never been a problem since.  The only other thing that is related to 
the ACIA and IRQ's in general is that the slot selector logic in the MPI's will 
block an IRQ from an unselected slot until such time as that slot becomes 
selected, which if the IRQ doesn't get through, might be never.

The fix for that is to jumper all 4 slots together at pin 8, and remove 3 of the 
4 IRQ pullup resistors along the front edge of the MPI's PCB.  *S9 can handle 
the rest, and other than those who might keep games multiple game carts in the 
MPI, I can't think of a scenario where that would effect an rsdos program.

-- 
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)
"You don't go out and kick a mad dog.  If you have a mad dog with rabies, you
take a gun and shoot him."
-- Pat Robertson, TV Evangelist, about Muammar Kadhafy