PicoRAM Ultimate

Description

PicoRAM Ultimate is the ultimate storage solution for single board computers (SBCs) / CPU trainers from the 70s and 80s.

It emulates:
- up to 4 2112 SRAM chips: it replaces the 512 bytes of stock SRAM in the Heathkit ET-3400; alternatively,
- a 2 KB memory expansion for the Heathkit ET-3400 (with expansion header installed),
- a single 6116 2 KB SRAM (e.g., for the Multitech Microprofessor MPF-1 / 1B / 1P),
- up to 4 2114 SRAM chips (e.g., for the Lab-Volt 6502 and Philips MasterLab MC6400 CPU trainers).

Using the built-in SD card interface, PicoRAM Ultimate allows you to save and load full memory dumps (including programs and data) to and from SD card, hence, rendering the cassette interfaces of these SBCs obsolete (if they even came with one; i.e., the ET-3400 required an extra memory expansion + IO box for the cassette interface, and the Lab-Volt 6502 doesn't come with one either).

Details

Supported

Supported machines (as of June 2025):

Multitech Microprofessor MPF-1, -1B, -1P (Z80)
Heathkit ET-3400 (MC6800)
Lab-Volt 6502 Trainer (6502)
Philips MasterLab MC6400 (SC/MP III = INS8070)
Busch Microtronic (well, kind of - this is really a bigger beast, see PicoRAM 2090)

2112 Emulation for the stock, unexpanded Heathkit ET-3400 (4x 2112 SRAMs = 512 bytes):

Heathkit ET-3400 Memory Expansion Mode (2 KBs of 2112 memory; requires extra GAL 16V8 as an address decoder):

6116 Emulation (Microprofessor MPF-1B with 2 KBs of 6116 SRAMs; also see PicoRAM 6116):

2114 Emulation (Lab-Volt 6502 CPU Trainer with 2x 2114 SRAMs, 1 KB):

Last supported machine - the Philips MasterLab MC6400 (2x 2114 SRAM, 1 KB), a SC/MP III (INS8070) trainer from ~1985:

Project Logs

Collapse

PicoRAM Ultimate 2nd PCB Revision Working!
Michael Wessel • 2 days ago • 0 comments

It just arrived yesterday evening, and I got up early this morning to check it out. It takes about one hour to assemble. A good stability test is the clock program for the microprofessor; if this runs stable for minutes, then everything is good wrt. timing and such. Passed!
Another Game on the Philips MC6400 - Guess the Number!
Michael Wessel • 2 days ago • 0 comments

Surprisingly interesting:
Load the NIM Game from SD Card
Michael Wessel • 6 days ago • 0 comments

I own the MC6400 for a while by now, but never did anything serious with it. Yesterday I typed in the NIM Game from the manual; given that that takes 20+ minutes I never dared to do that before given the lack of reliable storage. This has changed with PicoRAM now. The program is also on the program audio cassette that came with the machine, but I wasn’t able to load any of the programs from the 40+ year cassette. Really enjoying it now.
PicoRAM Ultimate and the Philips MasterLab MC6400
Michael Wessel • 06/05/2025 at 14:57 • 0 comments

PicoRAM Ultimate replaces the 1 KB (2x 2114) of SRAM in this SC/MP III (INS8070)-based machine from ~1985. PicoRAM facilitates dump and restore of full memory dumps to and from SD card. We are loading - and running - a simple 1digit hex counter demo program from the manual here.
Final PCB in production...
Michael Wessel • 06/04/2025 at 03:22 • 0 comments
Lab-Volt 6502 and PicoRAM Ultimate
Michael Wessel • 06/02/2025 at 16:48 • 0 comments

... we are getting there. 2x 2114 (1 KB) on this 6502-based Lab-Volt trainer. 6502 RAM timing is quite a bit more delicate and aggressive I must say! Challenging to get this right, took me a while. Now, basic RAM emulation is working, but I currently cannot fire up the second core for the UI (and reading the UI button and such) without causing "glitches" in the matrix umm RAM emulation. Still need to figure something out there. But, overall - it works!
6116 Emulation is back!
Michael Wessel • 06/01/2025 at 14:07 • 0 comments

Just a quick test that PicoRAM Ultimate can also replace the PicoRAM 6116 - check:
PicoRAM and ET-3400s without the expansion header
Michael Wessel • 05/31/2025 at 14:06 • 0 comments

Have an ET-3400 without the expansion header installed, and you prefer to leave the historic machine in original condition? Still, PicoRAM can be used on such a machine - simply use ribbon cables with connectors and plug PicoRAM into the ET-3400's 2114 SRAM sockets (two are sufficient; use IC14 and IC17), as shown in this video:
PicoRAM as a memory expansion (2 KBs)
Michael Wessel • 05/30/2025 at 15:41 • 0 comments

And now - 4 times the amount of RAM compared to the original stock system! Woohoo!
First PCB revision with minor flaws
Michael Wessel • 05/29/2025 at 15:50 • 0 comments

Well, I needed to cut a trace... but it's coming along: