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PG Designs made several ram expansion kits for Model 100 that ranged from 32K to 224K.
These kits added extra ram to a Model 100 in the form of 32K "banks", where each bank was essentially a whole separate computer. You use the extra ram by switching from one bank to another, and while in one bank you generally only have access to the files in that bank. Unlike some other ram expansion kits, the PG Designs ram did not disable or replace the built-in 32K. So, if you install the 224K kit, you have a total of 256K available, in the form of 8 banks, where bank 1 is your original built-in ram.

Pgdesigns1.jpg Pgdesigns2.jpg Pgdesigns3.jpg Pgdesigns4.jpg


Installing the bank-switch utility

  1. Back up any files you care about currently on the M100.
  2. Hard reset the M100 (wipe the ram): Hold down all 3 keys SHIFT+CTRL+BREAK and press RESET next to the serial port.
  3. Install teeny* on the M100. *(or any TPDD Client, aka DOS)
  4. Use teeny & dlplus* to copy "" to the M100. You can't transfer this file with TELCOM. *(or any TPDD Server)
  5. Run
    You will answer some questions.
    You will see "saving and moving program".
    Ignore the “FC error in 4” error.
    It will then delete the first 5 lines of itself and rerun itself.
    The program is now in lowmem.
    It will also remove the next 5 lines of itself.

At this point the program IS installed, though you can't see it.
It is an invisible program called 0MENU. (number zero, not letter oh)

Type 0MENU at the main menu and hit enter.

You should now see a new menu, and you can switch to another bank.

0MENU is only installed in bank 1 at this point.

When you switch to another bank, 0MENU won’t exist there, and so you can't use it to switch back.

To get back to bank 1, or get to any other bank, you can:

  • Power off and back on, which puts you back in bank 1. And since bank 1 has 0menu, you can go from there to any other.


  • Repeat the install procedure in every bank, so you have 0MENU in every bank.


0MENU also allows you to copy files from any bank that has 0MENU to any other bank that has 0MENU.

You can use INVISO.BA to make the program visible (MENU.BA), or invisible again (0MENU).


Find or create an mp3 cassette version of 0menu.

Create a 0menu injector similar to the teeny or floppy installers?

Credits / References

Thanks to Stephen Adolph for documenting the install and usage procedures and providing a pdf scan of the manual to an early 32k (single bank) model.



Lib-13-Reviews/BIGRAM.REV (see floppyco.txt from the here) 0menu v1.3 0menu v2.01 (from Richard Hanson below) See the RICHARD HANSON section

PG Design Data Transfer Utility v2.01 for 32K - 224K RAM Expansion units.
Please note: The MENU.BA file is not in ASCII due to embeded machine language code. You must download with xmodem or greater. The INVISO.BA file in ASCII.

Apparently these were also sold under the name Enterprise Systems.

Compatibility issue, and work-around, with the stock Tandy dos for TPDD and TPDD-2: