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Tuesday, December 19, 2023

Michael Wessel’s Raspberry Pi Pico-Powered 6116 SRAM Emulator Provides Classic SBCs a Main Overhaul

Classic computing fanatic Michael Wessel has turned a Raspberry Pi Pico into static RAM (SRAM) emulator and SD card storage interface for the Multitech Micro-Professor MPF-1B — bringing with it some severe quality-of-life bonuses.

“Give your Micro-Professor MPF-1B (and different machines) a flexible SD card interface — no extra cassettes,” Wessel writes of his creation. “Emulate 2kBs of 6116 SRAM with a Raspberry Pi Pico and use an SD card for storing and loading full reminiscence dumps! Its first use case is to emulate the U8 2kB system RAM from 0x1800 to 0x1FFF on the Micro-Professor MPF-1B. You will not want the cassette interface any longer — simply use the SD card.”

In the event you’ve a classic pc constructed round 6116 SRAM chips, this Raspberry Pi Pico-powered add-on is strictly what you want. (📹: Michael Wessel)

Launched in 1981 by Multitech, which nonetheless makes computer systems at the moment underneath the extra recognizable title Acer, the Micro-Professor MPF-I used to be a Zilog Z80-based single-board pc which aimed to show the core ideas of programming for the chip. The system’s output was proven on a six-digit seven-segment show, whereas applications might be saved — slowly — to cassette tape.

It is this gradual storage medium Wessel’s creation replaces, bypassing the machine’s personal storage system as a way to load and save on to RAM near-instantaneously — by utilizing a Raspberry Pi Pico’s RP2040 microcontroller to emulate the machine’s unique 2kB RAM chip.

“The primary problem was a scarcity of GPIO [General-Purpose Input/Output] pins on the Pico,” Wessel writes of the undertaking. “The 6116 [SRAM chip demands] a whooping eight bits of knowledge IO, 11 bits for the tackle bus, plus OE [Output Enable] and WE [Write Enable] — 21 GPIOs of the max. 26 that the Pico presents.”

On condition that Wessel additionally needed to supply a person interface with an OLED show, and storage on an SD card slot, further GPIO pins have been required — which have been offered by way of multiplexing the tackle bus utilizing two 74LS373 eight-bit latches. “The 2 latches are principally simply used for his or her tri-state/Excessive-Z capability,” Wessel explains, “I’m not even utilizing them as latches.”

This is not the primary system Wessel has constructed from a Raspberry Pi Pico as a way to supply quality-of-life enhancements for classic computer systems. Again in September he unveiled an add-on for the Busch 2090 Microtronic Pc System, the PicoRAM 2090, which aimed to work across the system’s painfully gradual 14-baud cassette interface with microSD storage.

The ultimate system works completely on an actual Multitech Micro-Professor MPF-1B — even pulling its energy from the host system immediately — and, Wessel notes, must also work “with different 6116-based computer systems.” Extra info on the undertaking is obtainable on Wessel’s Hackaday.io web page.

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