2024-03-02: The wiki ran out of disk space, so things were not working. This has been resolved by adding another 5GB of quota ;-) Thanks to Tim Lindner for reporting the issues. 2020-05-17: If a page gives you an error about some revision not being found, just EDIT the page and the old page should appear in the editor. If it does, just SAVE that and the page should be restored. OS-9 Al (talk) 12:22, 17 May 2020 (CDT)

Multi-Pak Interface

From CoCopedia - The Tandy/Radio Shack Color Computer Wiki
Revision as of 23:29, 27 March 2024 by Carney (talk | contribs) (Carney moved page Multi-Pak to Multi-Pak Interface: full / proper name)
(diff) ← Older revision | Latest revision (diff) | Newer revision → (diff)
Jump to navigation Jump to search
Looking for CoCo help? If you are trying to do something with your old Color Computer, read this quick reference. Want to contribute to this wiki? Be sure to read this first. This CoCo wiki project was started on October 29, 2004. --OS-9 Al

See Recent Changes. | About this site. | Join the E-Mail List or Facebook Group. | Contact me with updates/questions.

This page was last updated on 03/27/2024. Total Pages: 730. Total Files: 993.

Home / Hardware - Multi-Pak Interface

Multi-pak 26-3024 Grey
Multi-pak 26-3024 Grey
Multi-pak 26-3024
Multi-pak 26-3024 White
Multi-pak 26-3124
Multi-pak 26-3124 White

The MULTI-PAK is a peripheral that plugs into the expansion slot (cartridge port) of the Color Computer and expands it to handle up to 4 cartridges interchangeable and can be used one at a time without having to put out one another. This exchange of the 4 slot can be done without shutting down the computer, although sometimes a reset is required. You can even do some things with several at once.

The following models exist:

  • 26-3024 Grey
  • 26-3024 White
  • 26-3124 White
  • 26-3124A White

There are also custom made MULTIPAK and 8 Slot MULTIPAK (archived)

To use the MULTI-PAK smoothly with Color Computer 3, use this:

Upgrading 26-3024 MPIs typically replaces the existing PAL chip with a PAL/GAL chip programmed for the CoCo 3's addressing pattern, or redirect a pin on the PAL to a 74SL10 to limit the addressing.

Upgrading the 26-3124 involves trace cutting and wiring in a 74LS10 chip to change the addresses.

(From Cloud9's website): Here's a simple test that will determine if your Mulit-Pak has already been upgraded to work with a CoCo 3. From BASIC's OK prompt, type PRINT PEEK(&HFF90) and press ENTER. If 126 is returned then the Multi-Pak has been upgraded. If it returns 255 then it has NOT been upgraded.

To make a 20-3024 Multi-Pak Interface work with both a CoCo 1/2 and a CoCo 3 requires a piggybacked PAL/GAL with a switch to activate one or the other. I'm sure someone can figure out some circuitry to switch the 20-3124 type Multi-Pak Interface.

Neither setup is stable with the other CoCos. That is, once you upgrade to the CoCo 3 address set, your CoCo 1/2 will be unreliable with that Multi-Pak Interface.

26-3124 Multi-Pak Interface CoCo 3 Upgrade #1 (add in a 74SL10 chip to limit the address range)
26-3124 Multi-Pak Interface CoCo 3 Upgrade #2 (program and add in a new GAL chip to replace the logic of the PAL)
26-3024 Multi-Pak Interface CoCo 3 upgrade By Robin W. Drake (add in an 74SL10 chip to limit the address range)

Besides the two that provides Cloud-9 hardware Upgrade PAL Multi-Pak, but you have to send the MULTI-PAK.

The disk controller must be used in slot 4, and while you can use two disk controllers in the Multi-Pak Interface, problems exist as their addressing may conflict. This may be worked-around in some software.




A 74SL10 chip is used to provide 3 NAND gates that when combined as described limit addressing to not include the overlapping regions of memory. The 74LS10 can be mounted on top of another chip to provide provide power and ground, attaching pins 7 & 14 with pins 7 & 14 of the mounted chip. Bend out the other pins to not touch the underlying chip and run wires to the appropriate points to provide the logic needed, with one pin of the PAL redirected from its normal path. The points differ for the 26-3024 and 26-3124; both modifications outlined here (and in above links):

MPI Mod for coco3

Detail for 26-3024:

Detail for 26-3124:

MPI Mod for coco3 diagram