An in-system updateable MegaROM for the BBC Master 128

for bbc micro/electron hardware, peripherals & programming issues (NOT emulators!)
User avatar
Posts: 204
Joined: Tue Apr 26, 2016 9:17 pm
Location: San Francisco, CA, USA

An in-system updateable MegaROM for the BBC Master 128

Postby myelin » Fri Nov 10, 2017 10:31 pm

Another batch of Acorn hardware projects incoming... here's the first: the updateable master megarom, a replacement for the Master 128's MOS ROM, that can be reprogrammed by an attached microcontroller while the machine is running. The idea here is to make it easy to use and update ROM software in a Master 128, without having to use cartridges for everything. Especially convenient if you work on software like MMFS that cross-compiles from a different machine, as it'll allow you to flash your code into the chip directly from the machine you're building on.

The board has a CPLD and a 128KB-512KB flash chip (SST39SF010/020/040), and goes in the Master 128's MOS ROM socket. It has a header that can connect to a microcontroller for flash programming, and a header to go to a pair of switches, if you want to be able to switch operating systems on the fly, like with one of RetroClinic's DualOS/MultiOS boards.

The PCBs just arrived in the mail, and I should have all tested sometime in the next couple of weeks. Watch this space :)


It's open source (Apache 2.0 license) like all my other Acorn hardware, and the latest designs live on GitHub here: ... le_megarom
SW/EE from New Zealand, now in San Francisco, making BBC/Electron hardware projects for fun.
So far: fast serial port, 32k flash cart, USB cart interface, 3-cart expansion, Elk PiTubeDirect.

User avatar
Posts: 5364
Joined: Thu Oct 02, 2008 4:51 pm
Location: Manchester

Re: An in-system updateable MegaROM for the BBC Master 128

Postby danielj » Sat Nov 11, 2017 5:00 am

That is fab! Loving your work :D


User avatar
Posts: 2799
Joined: Thu Dec 13, 2012 8:46 pm
Location: Derbyshire

Re: An in-system updateable MegaROM for the BBC Master 128

Postby flaxcottage » Sat Nov 11, 2017 9:03 am

Wonderful idea.
- John

Currently running Level 4 Econet with BBC B, BBC B+ 128K, Master 128K, 4Mb A3000, 4Mb A3020, 4Mb A4000, 4Mb A5000 dual FDD; UK101; HP41CX setup; Psion 3a, 3mx and 5mx; Z88; TI-58c, TI-59 and printer, HP-16C programmer's calculator

Return to “hardware”

Who is online

Users browsing this forum: 1024MAK and 10 guests