I just received this Thomson TO8D that I bought on a classifieds site online:
These computers were pretty popular in France in the 1980ies and did not get exported much…
Hence you can find a lot of information in French but not much in English. So I’m writing this in English so that the rest of the world who may be interested (all 6 of you) can have some easily digestible information too ;)
I got this one to replace the TO7/70 that I had when I was a kid. The TO8D is compatible but much nicer. It’s basically the “end of the line” for the Thomson TO computers… (The TO9+ is also nice but more rare and more expensive).
- The TO7/70 was sold between 1984 and 1986
- The TO8D was sold between 1987 and 1989
Replacing the Fuse
This TO8D did turn on the first time I tried. Then I turned it off… and on again. Only this time I had inserted a disk in the drive… and apparently that triggered the floppy drive to try and turn at boot up and that… used a bit too much current… I heard a little pop and then nothing…
It was the fuse. It’s pretty difficult to remove the top cover completely because of very short ribbon cables attaching to the keyboard but it’s possible to access the fuse just by sliding the top cover to the right a bit.
This is the (new and replaced) fuse:
NOTE: it is very important to replace with the exact same fuse (0.315A 250V L ; L meaning “SLOW trigger”). There are slow and fast fuses. In this case it was a slow one which took a bit a research to find the same one to order online.
Now, before blowing my replacement fuse, I should probably go check the drive a little…
Opening the case
To further open the case, you need to disconnect those rather short ribbon cables connecting the keyboard to the motherboard:
It’s easier if you have a pair of pretty long pliers:
After that you also need to disconnect this – barely longer – cable for the top LEDs:
Then you can finally see the whole inside:
It’s interesting to notice that the power supply on on a totally separate board (brown) from the motherboard of the computer (greeen). That makes it easier to replace if needed. Nice :)
The floppy drive has an even shorter ribbon cable than the keyboard had:
After disconnecting the cables, there is only one screw to remove and then you can pull up the supports:
Motherboard components
Here is an unobstructed view of the whole board:
Because of the ST Micro processor (see below) and the “COM88” sticker, I am guessing this motherboard revision is no the first one from 1987 but a more recent one, perhaps from 1988.
What you find on the main board:
- The large bottom right chip should be a Motorola MC 6809E CPU. But it is an ST Micro “8809 9”. The second line says “EF6809EP” which is more like the 6809E reference that I expected… Searching Google, I found that Thomson Semiconducteurs themselves already manufactured these before ST Microelectronics was created in 1987.
The other interesting detail is that at this time it was not called ST Micro yet. Instead it was called “SGS Thomson” (merger of the Italian SGS and French Thomson Semiconducteurs). Yet, it already had the same “ST” logo as is used today in 2024…
Thomson EF6809E DataSheet: It seems the P at the end means “Plastic” package. - The ROMs in slots IW15 and IW17.
- 8 x KM41256AP-12 : 256K x 1Bit Dynamic RAM (so with 8 chips, this gives us a total of 256 kB of RAM).KM41256A Datahsheet: Clock timing requirements are noncritical, and power supply tolerance is very wide. Al inputs and output are TL compatible.
- 2 x MC6821P : Motorola Peripheral Interface Adapter (PIA) : MC6821 Datasheet : The MC6821 Peripheral Interface Adapter provides the universal neans of interfacing peripheral equipment to the M6800 family of microprocessors. This device is capable of interfacing the MPU to peripherals through two 8-bit bidirectional peripheral data buses and four control lines.
- Quite a few more ST Micro chips
- A few Thomson chips which may or may not have been designed specifically for the Thomson TO/MO computers (Thomson did a lot of different things besides computers…)
- A big cartridge adapter in the middle (which I’ll probably never need to use, since the TO8D has oboard ROMs)
And the under side of the top cover:
For reference, this is where the floppy drive goes:
Floppy Disk Drive
The floppy disk drive is a standard 3"1/2 double density double sided drive:
WIth a standard 34-pin Shugart interface:
However, it does not seem to have any jumpers to set a drive ID. So this particular drive can only be used as drive ID 0.
The top covers unclips like this:
This is the inside:
And here we can see it’s relatively easy to lift the top read/write head:
This makes it easy to cleen the heads with isopropyl alcohol.
After that I connected the drive to a greaseweazle on my mac and it worked absolutely flawlessly. I don’t understand wht having a disk a boot time would blow the fuse.
Anyways, I decided to put everything back together and proceed with testing…
Testing
The TO8D, like all Thomson computers, connects to a TV set of the time (and Thomson was a huge manufacturer of TVs) through a SCART connector which was absolutely standard and ubiquitous at the time in all of Europe. In France we also called in “Péritel” which is odd because SCART was already a French acronym (well maybe “SCART” actually sounds weird in French while it’s sounds “normal” in English…).
SCART allows for separate R, B and B signals. It blows anything else of that era out of the water…
This is what SCART looks like:
And this if the SCART plug on a “more modern” Samsung TV I got at the recycling center:
And it works:
Note how the SCART RVB signal allows for a nice an clean picture. Try that on a Commodore 64…
Yes I know there are stains on the picture. That is the LCD screen that suffered injuries at the recycling center. Don’t those guys have any respect, eh?
And finally testing the disk drive with a DIR and a LOAD:
yes, of course I had to do a SAVE and even format a disk with DSKINI before I could do that… but I was too excited at the time and forgot to take pictures! ;)
TODO
- Clean the whole thing
- The major issue I noticed during this initial test is that the “CAPS LOCK” key is stuck in CAPS… I’ll have to take apart the keyboard…
- Try on a CRT with a light pen (if I can find one…)