Introducing the MultiPET

[AndyG]

Introducing the Commodore MultiPET

I recently took my 40/80 column switchable motherboard (using the Comspec clone from Steve G) and modified it with the following capability
(why you may ask - well why not )

(1) standard 4032 with a SuperSoft HR-40 high resolution graphics card. Changeable character rom (change is software selectable via programming the user port) so can play the HAL games etc.

(2) standard 8032 (changeable character rom)

(3) SuperPet using the graphics keyboard (excluding the APL) working in both 80 column and also 40 column modes

• Needed to create custom edit roms for the 4032/8032 so it could switch between 40-col and 80-col displays, whilst still being able to use the high res board.
• New character roms to include the superpet rom. The Supersoft HR board works with inverse logic so all the bits in the character rom had to be inverted.
• Modify the SuperPET rom (D) so the keyboard mapping would work with the graphics keyboard (excl APL)
• Modify the SuperPET roms (C & D) so they can switch between 80 and 40 column modes
• I left the APL keyboard mapping alone as this is quite involved for little return (I have not used the APL code on the SP)
• Modify the Waterloo languages to work in 40 column mode (not fully tested)
• Added a reset switch so you can change modes easily.
• I used Steve G’s multirom board to select different character roms
• I used Jim B (Retro Innovation) 23xx adapters for a switchable editor rom and also switchable ROMs C and D for the SuperPET (40/80 col)

Hi res photos can be found on my flickr page

https://www.flickr.com/photos/138413...57719645686589

i haven’t uploaded pics here as there is a file size limit.

 

[dave_m]

Wow, this is amazing. So there is a SuperPet board in there somewhere?

 

[AndyG]

Yep it’s the original two board version (Computhink)

 

[AndyG]

MULTI-PET Goes OS/9

The last thing to fall to the Multi-PET was adding a MMU board (from RETRO Innovations) to the SuperPET configuration. This enables the PET to run Microware’s multi tasking operating system OS/9.

The history of OS/9 for the SuperPET can be found on Mike N’s webpage

http://mikenaberezny.com/hardware/superpet/super-os9-mmu/

I had to change the boot loader so it works with the Graphics keyboard layout but it works fine with DynaCalc (spreadsheet), Stylogrpah (word processor) etc.

Over time I have been given a number of application disks or have built up images using OS-9 disks for the trs-80 (posted on the internet). These include c-compiler, basic09, Pascal, Dynsastar….
For Those who have a SuperPET, it’s a simple modification to add the MMU board which opens up a different world of curiosity for the PET.

 

[AndyG]

I would add, OS/9 works best with the single add-on board SuperPET version. I have played with both variants and the two board add-on version (with the Computhink 64k add-on RAM board) can be troublesome. Mine has relatively 'fresh' TMS4116-15 RAM chips but if I put ITT 4116 RAM in there it does work so well. No issues with the Combo board variant.