AVM T1 Hacking
It was inevitable... the biggest system AVM built was the "T1", a 30 channel ISDN controller in a sleek 1U 19 inch case of which nothing more than the above marketing picture seems to exist.
One fine day I had to had one - and today is the day!
I was able to find a T1 on ePay which was not very well advertised so I had no "professional competition". Even I didn't spent a fortune it was a bit of gambling because I didn't knew what to expect.
Besides AVMs own T1 PDF manual there's next to nothing available in the Web - So this section is yet another WWW-exclusive brought to you by geekdot.com ;-)
Still, the docs said "a Transputer network with 9MB RAM" so I couldn't go completely wrong. That said, I was expecting SMD T400s at AVMs usual sluggish speed...
First look
When the box arrived first thing was getting out good ol' screwdriver and open the case...
...and I was very surprised:
- A socketed T425 - so that's another easy upgrade then.
- An external power supply (48V)! That's strange but also neat - no noise and next to no heat in the case itself
- Also, the board is very small... lot's of room left in the case.
That's done by intention as you could buy the T1-B, where "B" stands for the "Booster Board", yet another board with 4 more Transputers and another 8MB of RAM giving a total of 7 Transputers and 17 Megs of memory. Quite a setup for just an ISDN controller.
Sniffing around
Ok, this beast has to do something better than handling 30 boring B-Channels... Mandelbrot for example ;-) So let's see how this thing is/was supposed to speak to the outside world.
The manual is talking about an ISA or PCI controller-card which will be connected to a 9-pin Sub-D connector. Having a closer look to the mainboard where that connector is seated I discovered some other old friends: AM26C31 and AM26C32.
Aaaaalrighty, RS422 time... that's the same way my Tower of Power is transmitting its data. So I can use my TTL-to-RS422-converter I've built for the Gerlach card.
Out goes the multimeter and after a while I figured out the the traces on the board. For a better understanding, here's the "map":
Marked by the red arrows are the three Transputers: T1, a T425-25, is the "application processor" while T2 and T3 are more simple T400-20 handling the ISDN subsystem.
The yellow arrows mark the four links of the T425 - which is probably the reason why AVM used a 425 vs. their usual T400: this time they really needed 4 links.
Link0 is connected to the 9-pin sub-D connector (via the RS-422 transmitters/receiver) for interfacing to the PC.
Link1 and Link2 are directly connected to the T400s.
Link3 goes to the connector on the lower edge of the board. I bet this is where the "booster board" would be connected... not a hard bet, I admit.
The pinout for the 9-pin sub-D connector (female) is:
1 Link0-IN -
2 N/C
3 Reset-IN +
4 N/C
5 Link0-OUT +
6 Link0-IN +
7 Reset-IN -
8 GND
9 Link0-OUT -
As Link0-IN and Reset-IN are routed through two separate 26c32 I assume there might be more differential signals available. If time allows I'll dig deeper on this matter.
Do something Gromit!
Well then... a cable was built in a couple of minutes - some cursing and swearing about the differential polarity and then the exciting moment came: Let's see if it's really so easy again!
It is! And here's the ispy output for the T1 (connected to the "Gerlach card"):
Using 150 ispy 3.23 | mtest 3.22
# Part rate Link# [ Link0 Link1 Link2 Link3 ] RAM,cycle
0 T800d-25 288k 0 [ HOST ... ... 1:0 ] 4K,1 1024K,3;
1 T425c-20 1.6M 0 [ 0:3 2:0 3:0 ... ] 4K,1 4092K,3.
2 T400c-20 1.7M 0 [ 1:1 ... ... ... ] 2K,1 1022K,3.
3 T400c-20 1.8M 0 [ 1:2 ... ... ... ] 2K,1 4094K,3.
Some remarks about this:
- 9 MB is true. The "application processor" (T1) got 4MB while the two T400s got 1 (T2) and 4 MB (T3, obviously connected to the SIEMENS Munich32 Über-ISDN controller).
- While the built-in T425 is spec'ed for 25Mhz it's just running at 20MHz... what a waste of bang... and what an opportunity for improvement :->
- The linkspeed is at maximum... which one would expect with directly connected links. But with AVM you'll never know ;-)
- The RAM-speed is pretty good (compared to what they did to the B1) - even they just used 70ns RAM.
Next up: Having fun with Mandelbrot! Having just T4xx Transputers it can only use the integer algorithms (i.e. no floating point) but who cares for a quick start?!
It's working and showed another nice gadget: LEDs! Each Transputer has a tiny SMD-LED connected to it's Link-Out.
So having the T1 underneath the table I have quite a nice light-show while the three are working their a** off ;-)
Here's a video of Transputer-driven-Blinkenlights:
If you happen to have no access to a RS422 converter: Never say die!
Like said above, there's still Link3 available - normally meant for the booster-board - and it's pure TTL. All you need is a somewhat non-standard plug to this connector. Be creative but don't forget that unbuffered link connections only allow a distance of a couple of inches/centimeters!
The pin-out (so far) is, counting from left to right:
1 - 5V VCC
2 - Link3 OUT
3 - Link3 IN
4 - RESET
5 - ??
6 - ??
7 - GND
TODO:
- Change the T425
- Make the 30 front-panel LEDs blink
- Figure out for what the female 15pin sub-d connector is good for (not mentioned in the manual)
Previous page: The external Connector
Next page: Das Transputerbuch