Thomson MO5 - remake the Motorola Gate array with an ATF1508

[sporniket]

2025-09-21--02-alive.jpg (110.33 KiB) Viewed 162 times

So, this summer, I made this adapter to use an ATF1508 CPLD as a replacement of the original Motorola Gate array at the heart of the Thomson MO5. I just did the hardware part, I got the VHDL from one of the guy who did the reverse engineering one or two decades ago.

This is my first time with soldering TQFP and 0603 packages, and it went well.

2025-07-26--1-ga-remake-topside.jpg (134.92 KiB) Viewed 162 times

2025-07-26--0-ga-remake-underside.jpg (135.54 KiB) Viewed 162 times

There are two projects :

• The adapter project : https://github.com/sporniket/thomson-mo ... w--atf1508 there is an SVF file in the fusemap folder, to program the CPLD.
• A custom development board to program and verify : https://github.com/sporniket/thomson-mo ... ment-board this is a convenient rig to hold the remake, the USB-dongle of a FT232H, and an optionnal DC-DC 5V->12V converter to optionnaly force JTAG functionnality by feeding Vpp on the dedicated pin of the CPLD (you may need this when you buy from alternative sources instead of mouser/lcsc/rs/etc...). The "verify" part is just a witness LED that will blink at 1Hz when the CPLD generates the 1MHz clock signal.

I did not shot the assembly -seeing the top of my head for an substancial time would not be that interesting imho-, but I did shot the final stage of programming, installing the remake and switching the computer on :

[Icky]

Love it. The more we can replace / remake these custom chips in these old computers the better to keep them going.

Going to TQFP was interesting for me and I think that was my limit with my shaky hands. I never got the hang of the small BGA formats hence getting them assembled at the PCB manufacturer is now my option.

Nice work @sporniket

[tOriman]

Good job!
Another revived device running...

Thanx @sporniket

tOri

[HigashiJun]

Nice and neat.

Well done @sporniket !

[sporniket]

Thank you all.

I never got the hang of the small BGA formats hence getting them assembled at the PCB manufacturer is now my option.

Also with bga and qfn with exposed pads underneath, assessing a correct soldering jobs cannot be done visually anymore. And servicing would bé a pita for bga with the reballing step.