Tag Archives: hack


This is a hack which is very similar to the DesperRAM. It was borne out of pure despair, so it’s neither elegant nor very clever – but it works and that’s what counts.

During the “BOZO resurrection“, I had one specific PAL under suspicion to not working correctly any more. That PAL was soldered (i.e. not socketed) onto the board in a very tight spot, so I wasn’t able to cut the pins as close as possible down on the board.
I know, there are special pliers which can somewhat around corners, but my trustworthy Knipex (The pliers maker in the world, full stop.) can’t. So I had to cut the pins right at the PALs package – easy and quick.

The downside is that this method leaves you with a leg-less IC… and if you then decide it might be useful to read-out that IC (like I did) it’s time to slap your forehead :-/
But not so fast, young Padawan. Despair has the advantage that it normally can’t get worse, so nothing to lose. Even you cut the legs off you still can spot the tiny remains leading into the package. So why not trying to replace the amputated legs with artificial limbs!?

My initial thought was soldering new pins to the package, but the remaining connection is way too small to allow anything to be soldered to it but a human hair.
So I used a socket, turned upside-down, slightly bent the legs inward, squeezed the PAL between the sockets legs and carefully soldered the pins to the case-connectors. Finally I put small bits of wire into the sockets empty holes to create new pins to connect the whole thing to my GAL-programmer. Voilá: FrankenPAL


Yes, it looks horrible and I was quite sure that this doesn’t work but it just costed me 10 minutes, so what the heck, let’s try read-out that beast.

What should I say? It worked right on the first try… So never despair as long as you have a working solder iron 😉

Dissection time!

Ok, as I’m probably the last person on this planet fiddling around with the NumberSmasher i860, it was either “help yourself” or bust.

Given the fact that there’s an INMOS C012 on the card I tried my luck with the standard address of 0x150 and checked it with DOS’ crappy old ‘debug’. To my surprise I was able to talk to the C012, so it was very worth to investigate further.
So out went the good ol’ EPROM programmer and the EPROM of the card was dumped into a file.
I have 3 of those boards, two having a label on the EPROM saying “v1.1” and “BOOT_B2”. Both are identical… if you happen to own a NumberSmasher with a different label, get the dumpfile here for comparison.

That was easy, now the harder part: Disassembly. I had to revive my i860 machine language skills again, so it took me 2 days (on and off) to get a full understanding, what’s happening in there.
For those i860 assembly geeks among you, here‘s the fully commented code.

This “BIOS” is actually pretty simple. It’s just what I’d call a “PeekPokeStarter”. The main loop is waiting for a ‘command’ coming in by the way of the C012. This command can be either “0” or “1” as mentioned in the article on the previous page.

“0” means POKE (ie. write) and expects 4 bytes for the address and 4 bytes of data to be written (Both LSB first, Intel-style). So the full command reads: 0 00 00 00 20 78 56 34 12 or “write to address 0x20000000 the value 0x12345678”

So in consequence “1” means PEEK (ie. read) which just needs 4 bytes for the address to be read. The command would then be 1 00 00 00 20 or “read from 0x20000000”. The “BIOS” will then put 4 bytes to the C012 port at 0x150, which requires 4 reads from the PC side getting “78”, “56”, “34” and “12”.

Pretty simple, huh? But how can I start a program after it’s been painstakingly poked into the NumberSmashers RAM? Here’s the trick:

Poking to address 0x00000000 means start from the address given as data. E.g. “write to address 0x00000000 the value 0x20000000” is actually “start from 0x20000000”, or as command-chain: 0 00 00 00 00 00 00 00 20 – so beware of poking to 0!
Also, starting a program seems to disable the EPROM, so communication to the C012 is cut off if the running program isn’t handling this itself.

That’s about it. Nothing more in the “BIOS”… that’s why only 495 bytes(!) of the 8K EPROM are actually used. This simplicity leads to a very simple memory-map:

Base =  0xF8000000
C012-InData = [base] + 0x07
C012-OutData = [base] + 0x0F
C012-InStatus = [base] + 0x17
C012-OutStatus = [base] + 0x1F

Next task: Get a program running on the NumberSmasher.

[11/11/10] Great News…again! It was easier than expected… the first program running on the NumberSmasher-860! So read on in the next post…

Hacking the AVM T1


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 AVM 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 😉 (Ok since 2009 others discovered this page and also this cheap entry into the wonderful world of multi Transputing)
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:

  1. A socketed T425 – so that’s another easy upgrade then.
  2. An external power supply (48V)! That’s strange but also neat – no noise and next to no heat in the case itself
  3. 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 - T1 Link3 OUT
 3 - T1 Link3 IN
 4 - RESET
 5 - T3 Link1 OUT
 6 - T3 Link1 IN
 7 - GND

[UPDATE 11/14/10] Again, with some ePay-Luck I got another T1… and it again was some kind of lottery… and I had luck! This time it’s a T1-B!! This means, the “booster board” is installed. So opening the case, it looks like this. On the right the normal T1-board, to the left, “da mighty booster board” 😉 I’ll call it “BB” from here…T1-Booster-Full

As expected, it’s connected via Link-3 of the T1 Board. On the lower edge of the picture you can spot the power-supply “module”. It’s longer than in the T1 configuration and provides 3.3V/GND to the BB, i.e. the BB is 3.3v only!!

Here’s the BB alone:


All in all the BB is more modern than the T1-board. Very suspicious are the JTAG connector on the lower left having its lines connected to a EEPROM (AT28V256, right edge of the BB board, above the row of RAMs). Further up, left to the CPU nearby is a pad with the lable “Boot from ROM/Link”. I wonder what the default is and what’s inside that EEPROM – will investigate later.

Most importantly the BB board features 4 ST20450 processors, which aren’t INMOS products anymore. They were designed by ST after they bought INMOS. For short, the ST20450 is a T425 on steroids. More on-chip RAM (16K), higher clocking (40MHz) and some more instructions.
Each ST20450 has its own 2MB of RAM and a GAL handling the memory etc.. Here’s a close-up of a single ST20450 “module”:


Mind the careful markings/labels on the board. The CPUs are numbered (“Processor 3”) and there are pads for Links etc.

Finally, I currently have no tools to check/use ST20450 processors. ispy finds the Transputers on the T1 board but freaks-out when it pings the ST20s.

Here’s another new addition: A picture of the official T1-PCI interface. It contains a PCI-controller (the big IC) and a XILINX FPGA… probably containing a synthesized C011.



Jonathan Schilling also playsplayed around with a AVM T1 including the original ISA controller card… and he‘s making made very good progress! Check out his page over here (German)!
[2015, Jonathan quit ‘the scene’ and handed over all his equipment]


  • 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)

Here’s how to access the LEDs at the front – thanks to Michael Brüstles research:

typedef unsigned long int u32;

 *  wr                               0-01    __ EN __ __-__ __ __ SY
 *  wr                               0-10    08 07 06 05-04 03 02 01
 *  wr                               0-11    16 15 14 13-12 11 10 09
 *  wr                               1-00    24 23 22 21-20 19 18 17
 *  wr                               1-01    SC ST 30 29-28 27 26 25
 *  rd                               0-01    readable ... content unknown

int main( void ) {

    u32 *p = (u32*)0x80700000UL;

    p[ 1 ] = 0x40;  /* enable all leds 0x40 & Sync 0x01 */
    p[ 2 ] = 0x05;  /* Led01-Led08 */
    p[ 3 ] = 0x00;  /* Led09-Led16 */
    p[ 4 ] = 0x3F;  /* Led17-Led24 */
    p[ 5 ] = 0x92;  /* Led25-Led30, System, S-channel */

    return 0;

Fixing scratched traces

This is the price you have to pay if you’re into real men’s hardware:

Being (falsely) identified as “old crap”, some cool things end up in the dumpsters… or worse. Being tossed around in some storage for years, probably stacked with other cards and boards, it might happen that some traces on the outer layers got badly scratched, thus making the board/card non-working. Here’s how I try to fix scartched traces… and most of the times it works:

First make sure that the circuit path (trace) is really broken – I just may look like, but isn’t.
To do this you need a volt-meter. Follow the suspected trace in both directions until you find a pin or through-hole it is connected to. Use these two points to test if the trace is still connected.

Ok, damn, it’s broken 🙁 You need three things:

  1. A sharp knife or scalpel
  2. Adhesive tape (Scotch, Tesa or whatever it’s called in your corner of the world)
  3. Conductive (silver) lacquer

Conductive-what? Conductive lacquer is actually a cool thing to play with… but be prepared: It’s not cheap (about 9-10 Euros). It comes in tiny bottles or as a pen, which is even more expensive (20+ Euros). The bottles look like this (lacquer and diluter):


Ok, the process is quite simple:

  1. Use the knife to scratch-off some of the coating lacquer on both ends where the trace was “cut” until you see some copper shining through.
  2. Check with your volt-meter that you actually have contact with one end and e.g. a pin on the other end of the trace. Do this for both “halves” of the cut trace.
  3. Mask the place you’re going to ‘heal’ with your adhesive tape – this prevents the conductive lacquer to run all over your board.
  4. Apply the conductive silver lacquer onto the spot you’ve just masked and let it dry (read the manual that came with the lacquer – yeah it’s unmanly but nobody will see you ;-))
  5. Using your volt-meter, check again. This time from both ends of the complete trace.

If you’ve done everything right, the  trace should work again – and so does your card/board! Yay!

Here’s how my badly scatched MiroHIGHRISC looks like in certain places – can you spot the little silver dot?


Final hit: Some lacquers are quite thin on silver (blame the manufacturer) so after some days the spot you just fixed might become unreliable. In this case you might repeat the procedure to get more silver to that spot.

Removing pin rows

Removing pin rows…doh! It took me quite some time to figure out a working solution for this problem, so I thought it might be useful to you some day, too.

Some idio^h^h^h^h not so clever person cut off all the pins on one of my DSM860 RAM boards – I probably will never figure out why (may a lightning hit him!). Besides 8 of the pins all other 74 (!) where cut, rendering the ram card non-functional (it’s the memory bus connector).

Here’s a (blurry enlarged) picture of the mess:


I started to desolder some pins from the back-side of the card but soon found out that the solder was too old to be removed the classic way (desolder pump & wick). Also, that pin-row (41×2) was one piece, so I would have to completely remove all the solder before I would be able to pull the part from the card.

After some thinking I came to this solution, which worked quite good:

First you need to cut away the plastic part from the top of the board. I used a very fine and sharp  caliper to cut away one pin after the other (i.e. like a single jumper).
While doing so be careful not to cut into the board!
Then pull or push the plastic pieces from the pins, again one after the other – I used a thin knife pushed under the plastic an gently wiggling it over the pin.

When done, it should look like this:


You may spot that some pins are missing already – that’s because my previous desolder tries sometimes seemed to work. Still, I couldn’t avoid that some pins got bent. This is the time for my secret repair tools: Syringe needles!

Second, get two kind of needles:  Gauge 18 and 20, that is 0.9mm and 1.2mm, color code yellow and pink. Cut off the tip of the needles and use a rasp to make the edge straight and clean. They should look like this then:


The bigger needle (G20) is just perfect to be completely pushed over a pin which then can be bent into any position without the risk of breaking it off – it works like this:

(This is just a showcase picture with a different board, the needle needs to be pushed all the way down over the pin)

So straighten all the pins into an upright position. This will be important for the next step!

Now put your board into a vertical position (e.g. fixed by a bench vise or clamped between your inner thighs ;-)), get out your solder iron and the G18 needle – this needle should be just small enough to fit through a pin-hole.

This is the third and last step. Place the G18 needle over the pin you like to desolder on the back-side of the board like showed here:


From the other side you’re touching the base of the pin with your solder iron. As soon as the solder starts to melt gently push the needle onto the pin.
If everything works like it did for me, you will push the needle through the board, including the solder and the pin you’ve planned to remove!

The great thing with this is that the needle (being made of steel) does not stick to the solder. As soon as the needle got a bit colder, you can easily remove the pin as well as the excess solder from the needle with your fingers!
Now carefully pull back the needle through the board and you should have a nice and clean through-hole in the board. If not, a final cleaning with a desolder-pump or wick should do it.

This needle-trick also works brilliantly with empty pin-holes which got filled with solder. Just place the needle on the pin-hole on one side of the board, heat up the solder on the other side while pushing the needle. Pop! There goes the solder!

As said, this technique worked great for me. All 82 pins got removed, a new pin-row was soldered into place and the card is now working like a charm.

Still, do this at your own risk!
I’m not going to be taken liable for any damage to your board or your health!
If your unsure if you are able to perform this stunt, don’t do it!
Practice with an old scrap board/card before you fiddle with the “real thing”!


You might have been in the same situation: Some piece of old hardware could be upgraded (aka pimped) with more RAM, but there’s no place in the world to get that type of RAM needed.

In my case it was 1Mx4 DRAM in a DIL packaging. It’s hard to come by those in a ZIP packaging – sometimes used on AMIGA RAM cards – but DIL is next to impossible.

Well, when 1Mbit RAM chips were introduced, the industry switched to SIMMs anyway… and that’s where you find those. For the DespeRAM, SOJ packaging is what you want. SOJ (sometimes also called J-Lead) means there are short pins on the IC but they’re bend inwards under the chip… pretty much like PLCC pins.

What you need for this stunt:

  • Desperation. Lots of it.
  • A hot-gun (for getting the SOJ chips off the SIMM module)
  • A fine tip on your solder-iron. Very thin solder led (e.g. 0.5mm)
  • DIL sockets for your desired piece of crap^h^h^h^h vintage hardware
  • Wire, also thin (I used 0.6mm)


Clean desk. Good lighting. A steady hand (no coffee or drugs – I assure you, it won’t work. I tried it ;))

Ok, so first of all get out the hot-gun and carefully get the ICs off the module. Here’s a single chip and the socket it should be mated to


Bend the pins and straighten them. I used a needle to pry the pins upwards a bit and did the rest with tweezers. Now you have the exact spacing of the pins on your chip. Use that for building a “pin aligning tool”. I’ve used a piece of plastic and a fine saw to cut 10 grooves into it. When done, it looked like this:


Now find something on which you can fixate the chip to (still being movable). I used a block of wood and a rubber band. This worked quite well. This way, you can always adjust the position of the chip when needed.
It’s time to cut some pins. For the start I went for about an inch long – place them into your self-made tool and fix them with a piece of self-adhesive tape (Scotch in USA, Tesa over here ;)).
Now put some solder on the chip’s pins as well as on the freshly cut DIY-pins.
Carefully position your tool so that the pins do have good contact.

If you did everything right, a short contact with the solder iron tip should be enough to solder the new long pin to the original one. When you’re done with all pins it should look like this


As you can see, I did already start to bend the new pins to fit into the socket. It’s a bit try-and-error to get the right angle. Be careful to avoid the pins touching each other or even break when being bent. Re-fitting a single pin can be a major pain in the a**!
Now you need to cut the pins into a reasonable length. First bend them into position – constantly checking against the socket. When all pins are ok – start cutting from one side to the other, bit for bit until you got the perfect length (Use the first chip as a model for others which might follow).

The seating is a bit difficult as you can’t use maximum force to push them into the socket. I used a fine caliper to actually pull the chip into the socket.

Due to the angle needed, the chip will hover quite a bit above the socket. I guess you can go lower if you go for a 90° bending – I didn’t have the patience.
Double check all connections from the original pin to the one on the socket. Also check for shorts!


Here you have it, the ugly Franken-Chip. But hey, it didn’t cost me a dime!
That said, after soldering 160 pins, bending them and carefully pulling them into their sockets… I guess I won’t do it again 😉

Das Transputerbuch

There was one major german book about transputers called “Das Transputerbuch”, written by Uwe Gerlach (ISBN 3-87791-019-X).DasTransputerbuch
What made this book special was that it included an unpopulated 8-bit ISA card for a transputer and 1MB RAM, fully B004 compatible.
Additionally, there were schematics provided to build a host-adapter for several homecomputers of that time (C64, Apple II, ATARI ST and Commodore Amiga).

I was able to get one book off ePay which was still includung the printed circut board and a 360k floppy containing some sample sources and a rudimentary assembler.
So I’ve polpulated it, found some mistakes Gerlach made and made it somehow run.

This is how the card looks


It’s design is pretty simple – at least compared to the efforts been taken with the i860 cards on this page. The simple design is also because the Transputer has nearly everything included… so what you see is:

  • The right half is the ISA-bus and link interface. The rightmost and longest IC is a C012 connecting the 8-Bit ISA bus to link0 of the Transputer. Everything else are buffers & drivers.
  • The left half is -besides the Transputer itself- just 1MB RAM and some address-logic. The card would also work without having this side populated using the internal 2 or 4k of the Transputer.

C’est ca. As said, prety simple.

The mentioned bugs of the card are:

  1. The orientation of U11 and U12 are wrong on the print on the PCB and in the book, check the photo for them.
  2. There are no holes for the capacitor near to U28, you will have to solder it to the corresponding pins on the back of the PCB.
  3. The crystal oscillator U12 has its pin-1 not-connected, but it is connected to ground on the board. My crystal oscillator didn’t generate a clock signal, when pin 1 was connected to GND, although it normally shouldn’t matter.

Still, there was a persistent problem with the external 1MB RAM. It was detected by mtest but depending on the Transputer-type used and some randomnes, it never was checked as being ok.
Thanks to Michael Brüstle and his skills it’s working now – he replaced some capacitors and strenghtened some ground traces but it’s still not clear what the real reason was.

Here’s the back of the card – looking like a snake-pit now 😉


AVM B1 hacking


Transputers were created to control everything. They were not just CPUs… they could do the video output, control interfaces or even storage devices. So no wonder there were ISDN and SCSI controllers available using transputers.

One of those transputer-sporting controllers was the AVM B1 active ISDN card. Back in the PC-AT days, handling the ISDN protocol and traffic could easily bring down your super-cool 80386/25 without a problem, especially if this machine should also fulfill server tasks.
So active (vs. passive) ISDN cards were the cure to that issue. They featured a CPU of their own with some RAM to buffer the data coming in at the maximum ultra-fast rate of 128kbps 😉

In case of the the AVM B1 the CPU was a transputer (T400) and that had reign over a whopping 1MB of RAM! When the card was installed and the DOS driver booted, it actually loaded the transputer code onto the card like any normal transputer card would be fed with code – behaving like an Inmos B004 card and even using the same port addresses.
So in fact, the AVM B1 is a transputer card featuring an ISDN-part connected to one of the transputers links.

Using the usual tools for finding and checking a B004 compatible card shows this

> ispy | mtest Using 150 ispy 3.21 | mtest 3.21
# Part rate Link# [ Link0 Link1 Link2 Link3 ] RAM,cycle
0 T400b-20 43k 0 [ HOST ... ... ... ] 2K,1 1022K,6.

Weapon of choice

Ok, cool – so where do I get this card?

Well, AVM is still very alive-and-kicking but they’re not building these cards (using transputers) anymore… even if they wanted to, Inmos/SGS killed the transputer back in 1993. So eBay is your friend.

Anything to watch out for?

Yes! AVM build(s) 4 major versions of the B1: V1 to V4.
V1.x – Available as ISA and MCA version. The perfect choice! Everything important is socketed, no SMD parts.
V2.x – ISA version only. CPU & RAM is SMD. Ready to play with but not much to mod.
V3.x – ISA & PCI version. Updated version, same features like V2.x
V4.x – PCI version only. No transputer anymore. “StrongT” Controller… might hint towards a StrongARM based thingy.

Again: If you want to do all the hacks described here you have to get a Version 1.x card!

Enhance it! This is the easy part…

Ok, so I assume you fought hard to get a V1.x B1… it should look like this:
(If you acquired an V2.0 card which is smaller and has lots of SMD parts on it, check out Jonathan Schillings page (German), who did all the mods described here with a V2.0 card)


If you have your card in front of you, you might spot some differences. These are the first two and most obvious “mods”:

  • Change the T400 CPU (e.g. to a T425 or even T800)
  • Add more RAM

The T400 is OK to begin playing with this card, but it only offers 2K internal RAM (vs. 4k in the T425/800) as well as it has only 2 links: One connected to the C012 (and this going to the ISA interface) and one is available. I was under the impression, that AVM might use the other link to interface to the ISDN part, but that seems to be memory-mapped.
Changing to a T425 gives you more internal RAM (=speed) and the possibility to use 3 external links to talk to more connected transputers.
A T800 would be the top-of-the-hill, featuring an FPU which will speed up your Mandelbrot tremendously.

So here’s my T425 which replaced the stock T400. At about 8-10 Euros you should be able to get one at ePay…


Next up, the RAM. Albeit the standard 1MB are plenty enough for nearly all fooling-around you might plan, there’s another Axel-Law to be followed: “If there’s an empty socket, fill it!”.
Also if you’re going serious and think about running the Helios OS on this card, you’ll better have 2MB!
You need to get eight 256Kx4 chips – they’re pretty common. They should be faster than 100ns… you’ll read later why.


The eagle-eyed reader might spot the different makers of the RAM chips. That’s because I’ve salvaged 2 old ISA-VGA cards (each 512k) for the chips. All are spec’ed at 80ns.

Another run of the transputer find/check-tools now shows this

> ispy | mtest

Using 150 ispy 3.21 | mtest 3.21
# Part rate Link# [ Link0 Link1 Link2 Link3 ] RAM,cycle
0 T425b-20 43k 0 [ HOST ... ... ... ] 4K,1 2044K,6.

Not bad, huh? But there’s room for improvement… the RAM is accessed extremely slow, set to 6 clock cycles which is very conservative, even for 100ns RAM parts.

Faster RAM – The not-so-easy part…

Ok, up to here it was a piece of cake, wasn’t it? Now we’re switching to hard-core mode 😉

RAM-Access speed-up

For this you’ll need

  • Some soldering know-how – and a solder-iron of course
  • A calm hand
  • A continuity-tester or multimeter
  • A thin cutter
  • the pinout of a transputer (available in the data sheet (PDF))

As said before, the RAM access is very slow. It’s set to 6 clock cycles which is recommended for 150ns parts even at 20MHz. So for a start we should be safe going down to 5 cycles even with the standard 100ns RAM chips…
The RAM is controlled by the transputer itself – something the Intel-World introduced with the AMD Opteron years later!

When booting, the transputer checks how his “MemConfig” pin (position C8) is connected to the MemAD[3-7] pins to determine the RAM speed. The AVM B1 has its “MemConfig” connected to MemAD7 (position K10) which we want to change to MemAD6 (J8) in the first step.
The AVM B1 is a 4-Layer card and unfortunately the wire connecting those two pins is running in the 2nd layer from the back.

To find the trace we have to cut, hold the card in front of you looking at the component-side – like the first picture on this page. Now flip it vertically. You’re looking at the solder-side, the external connectors pointing to the left.
A closer look at the transputer pins shows you where to cut and the wire connecting “MemConfig” with “MemAD6” – Pin A1 is in the upper left corner, counting down[123456789,10], letters right [ABCDEFGHJK]!


The cutting is a delicate thing to do. So be very careful not to cut too deep. I did it by cutting carefully once or twice and then checking with a continuity-tester if MemConfig and MemAD7 are still connected. Repeat until the connection is broken.
If everything went fine solder a wire between the two pins. Don’t make the wire too short, so we can change/move it anytime later. Another test shows this now:

Using 150 ispy 3.23 | mtest 3.22
# Part rate Link# [ Link0 Link1 Link2 Link3 ] RAM,cycle
0 T425b-20 43k 0 [ HOST ... ... ... ] 4K,1 2044K,5.

Yay! RAM’s accessed a bit faster now.

If that works and you’re like me (squeezing out the last drip of everything) you can try connecting to MemAD5 (J9). It worked for me.

Faster Link Speed – Not for the fearsome!

The next thing being rather sub-optimal is the link-speed… 43k/s is dran slow.

Using 150 ispy 3.23 | mtest 3.22
# Part rate Link# [ Link0 Link1 Link2 Link3 ] RAM,cycle
0 T425b-20 43k 0 [ HOST ... ... ... ] 4K,1 2044K,5.

That’s because it’s locked to 10Mbit/s by AVMs design even 20Mbit/s would be possible. Again, the transputer gets its configuration during boot-time via special pins. In this case LinkSpecial(A2), Link0Special(B4) and Link123Special(A4).

Not a big deal, but in case of the AVM B1 it’s not solvable by simply putting those pins high or low. That damn card is -again- a multilayer card and one of those layers is a ground-layer. No way in cutting a trace here.
The only solution is an in-between socket… a calm hand and pincers >:-)

socket_topOk, first you have to get another 84-pin socket. It’s not so easy anymore to find those… luckly, I had one spare collecting dust.

You might find an alternative socket meant for a Motorola 68881/2 FPU – but make sure it also has the inner pin-rows connected. Normally the 68881/2 has 8 pins less!
Another possibillity would be making a socket by glueing 10×1 pin-rows together. Not pretty but should do the job.

For the second step, you’ll need a caliper and (again) the transputer pinout. Orientate the socket so that pin-1 is in the upper left corner (the picture above shows this by the angled-corner in the center of the socket).
Now identify the pins LinkSpecial(A2), Link123Special(A4) and Link0Special(B4) as well as one VCC-Pin of your choice (I went for C2). We need to connect those 4 pins, pulling all Link[n]Specials high… which gives us 20Mbit/s link speed!

Note: If you plan to use the B1’s external links, you might consider not to change the external link-speed – read more about this in the next chapter.
In this case do not change Link123Special(A4).

So carefully cut the thin part of the pins A2, A4 (see note above!) and B4. Use a rasp/file to shorten the pin down to the thicker base (so the remaining part can’t connect to the original socket).
This is how it looks already having A4 & B4 cut off, A2’s still due (all marked red) – Do not cut the VCC-pin (C2, marked blue)! :


When everything’s nicely cut, use a wire to connect them together – it’s a bit tricky to solder between the pins, so use a fine tip.
When you’re done, the socket should look like this:


Now double check the modded pins for shorts to their neighbours!! Not doing so might kill your transputer/card!!

Cool! Were half done. For the third step we need to adjust the other side of the link accordingly. “The other side” is the Inmos C012 link-adaptor sitting in the lower right corner of the card -close to the ISA connector- labeled “IMSC012-P20S”.
Identify pin-15 and use a thin caliper to cut its leg as close to the board as space allows it. Bend the remaining leg up and check that there’s no connection to the card anymore.
Now solder a wire going from pin-15 to some VCC source. I’ve chosen Pin-20 of the 74ALS245 next to the C012. This is how it looks on my card:


[Note: Make your wire long enough so you can reach some GND pin with it. So you can reverse the mod easily.]

We’re nearly there! For the forth and last step, plug your transputer into your in-between socket and the whole thing into the original socket on the card like this:


Done! If everything was done right the usual tools should give you some serious number (well, it’s still far away from the theoretical 1.7Mbit/s, but at least 8.8 times faster than before):

Using 150 ispy 3.23 | mtest 3.22
# Part rate Link# [ Link0 Link1 Link2 Link3 ] RAM,cycle
0 T425b-20 378k 0 [ HOST ... ... ... ] 4K,1 2044K,5.

378k/s is faster than my crappy Gerlach-card (@239k), even the AVM is also just using 8 data-lines of the ISA bus (being a 16-bit card it only uses 4 lines from the AT bus… for IRQs 10-13).

So… what else can be done?

The external Connector

The AVM B1 v1.x cards feature a mysterious (green) connector:


It’s undocumented… up to now 😉 I just started tracing all the connections, but I’m happy to say that even AVM did everything possible to cripple the B1 card, they did not dumb it down completely:

Link[123] & Reset (not inverted!) are brought to the outside!! Error and Analyse are hold to GND, though.

Note: That said, AVM wouldn’t been AVM if they didn’t save a dime… the external links are buffered (at least) by a comparably slow 74BCT541 octal buffer.
This offers a signal propagation delay of ~9ns while INMOS recommended to use “F” type buffers, which offer a speed of about 3-4ns. So 20mbps are too fast for this chip. 10mbps should work though.

Here are my findings so far: [work in progress]

I started counting pins from the transputer, zig-zag, downwards. Interesting things coloured green.

1 2
o o
reset o o
o o
o o
o o
o o
o o (to its pin 10)
Link3Out o o
Link2Out o o
Link1Out o o
Link3In o o
Link2In o o
Link1In o o
GND o o
o o
GND o o
o o
33  34