Michael Wessel's PicoRAM Ultimate Vintage SBC Expansion Doubles Its RAM Emulation to a Generous 4kB
Fancy tricking out your 6502 or MC6400 trainer, Micro-Professor, or Heathkit? Here's the board for you.
Vintage computing enthusiast Michael Wessel has launched a second revision of the PicoRAM memory and storage emulator for vintage computing systems — and the PicoRAM Ultimate Rev. 2 increases its RAM emulation capabilities to a generous-by-contemporaneous-standards 4kB.
"PicoRAM Ultimate Version 2 […] fixes the PCB RE signal flaw on the IO header, routes more address lines into the decoder for more fine-grained control over the PicoRAM address range, and bumps it up to 4kBs," Wessel explains of the changes in the latest revision. "More isn't possible because of the GPIO [General-Purpose Input/Output] shortage on the [Raspberry Pi] Pico, and the address bus is already multiplexed. I need the other GPIOs to drive the other functions (databus, SD card, display…)"
The PicoRAM Ultimate builds on Wessel's earlier PicoRAM project, which was designed to turn a low-cost Raspberry Pi Pico RP2040 microcontroller development board into an SD card storage interface plus 2kB RAM expansion for the Micro-Professor MPF-1B. The Ultimate, as befits its name, expands the scope to additional systems and increases the emulated RAM to 4kB where possible — offering emulation of a single 6166 SRAM chip for the MPF-1 family, up to four 2114 SRAM chips for the Lab-Volt 6502 and Philips MasterLab MC6400 trainers, and up to 4 2112 SRAM chips for the Heathkit ET-3400A.
The board is also capable of ROM emulation, and includes — as did its predecessor — SD card storage. "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," Wessel explains, "hence rendering the cassette interfaces of these SBCs [Single-Board Computers] 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 does not come with one either.) It can also act as an IO extension and provide text and graphics for some machines."
The project is documented on Hackaday.io, with hardware design and production files plus source code available on GitHub under the reciprocal GNU General Public License 3.