The AM-B404

Here it is, my latest baby, the goal I was aiming for since years (4 to be exact) – not only to get more TRAMs for my systems but also to break the insane price spiral developing in the last years on ePay and other places. >300$ for a TRAM is crazy. Do not pay that amount! Even $100 is too much.

Update: Final version finished! Click here or scroll down for more.
Update 2: You can buy one, if you like…


My first CPU TRAM called AM-B404 in reminiscence to the IMS-B404 which comes closest to its specs:

  • Size-1 TRAM
  • 2MB low-power SRAM
  • 2 LEDs showing the Transputers status (running and error)

Well, the original Inmos B404 had 2MB DRAM, too (and additional 32k SRAM) but was a Size-2 TRAM and LEDs weren’t available on any Inmos TRAM… and we all know how important LEDs are! 😉 Contrary to the IMS-B404, the AM-B404 is low-profile, SRAM-only, so the whole RAM is accessed at 3-cycles vs. the IMS-B404 4-cycle DRAM.
Using a 6-layer PCB and all-modern SMD parts (well, as modern as 5V parts can get) the power consumption is a bit lower, too. I’d say about 100mA for the whole Board (no Transputer of course). Finally, there’s an easy access solder-bridge on the backside to set the CPU clock (20/25MHz).


This is just the 1st prototype. After thorough testing, I will optimize its layout a tiny bit and give it the proper shape of a TRAM. When that’s done, we’ll see how I can make you a realistic price offer.


From Shenzen with love. The final PCB designes arrived and the first test went perfectly fine.


And here are the first 4 PCBs waiting to be finished with the Trough-Hole parts (i.e. Transputer Socket and TRAM Pins)… 100 solder-points in total… per TRAM. That’s quite a bit to solder :-/



Finally, here’s a short video showing the prototype AM-B404 in action (running Helios on my Inmos B020). The “exciting” thing is the blinking green LED which shows the CPUs activity. There’s even some brief red LED access (error) during boot-up which is triggered by Helios scanning the Transputer network.
The bright blue LED to the left is the T2i2c TRAM, so all TRAMs on the B020 are built by me now 😉

Want one?

If you hate the greedy ePay prices like I do, drop me a mail. I might have some AM-B404 left… even with T425/T800 Transputers.

Can I have the schematics?

No, not yet. Sorry. I have to break-even on this first…
Since people discovered there’s serious money in the retro-scene, some ‘smart guys’ started to clone every PCB they can get their hands on and thereby steal the initial investment which the original creators made.

I sell them a bit over the price they cost me to produce. And trust me, you won’t be able to go lower than me:
It’s a 6 layer PCB. ENIG Gold.
Sadly SRAM did not get cheaper, really. Especially the (obsolete) 5V 512kx8 I’m using were lately discovered by other projects to be very convenient and so the battle for SRAM was on. If you’re lucky you might get one for 4€… and you need 4 of them.
The 16 pins used to connect the TRAM to its carrier are very special. You have to buy them by the 1000s – 0.15€ a pop… you do the math.

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