Friday 6 October 2023

A SuperPAK Coreboard

A bit of a discussion on the Microbee forum got me thinking it'd be nice to do a simple ROM coreboard. No flash, no CF, no SD, just lots of straightforward biggish EPROMs. Then load games in, write a shell, and play.

I had a look at what was available around the time the Bee was still selling, and you could get 27512 EPROMs (64K x 8 in a 28 pin package) and skinny 6264s (which the Microbee premium baseboard uses). As it happens I have a whole pile of both.

So a few days work in KiCAD yeilds plunder:

One has to be considered in using round the tracks in KiCAD. Each time you run it it seems to take about twice as long as the last time, so if you do it too much the board becomes impossible to edit.

Edit: Yay, boards have arrived!

And assembled using parts I had to hand. Note no battery backup as yet, plus I didn't have a 74C or 74HC14, so have substituted a 74HC04 (not schmidt trigger). As a result reset is really hit and miss.

In amy case, it boots, both on non-premium and premium baseboards, and I can run Emu Joust and access PAK. I shall order the remaining parts through the week.

An adaptor board to simplify software development - this allows us to plug a single 32 pin EEPROM in in place of four 28 pin EPROMS, and can be assembled with a zif socket.