Cyberspice @cyberspice@oldbytes.space

Been thinking about how to bodge shadow graphics memory on to the memory expansion for the BBC I designed. I have 4 boards left so it should be easy to cit a few tracks and add a board with a static RAM and PAL for the additional address decoding. A few bodge wires and cut tracks will be the rest. If it works I’ll layout a new board!

And it seem to be working perfectly. 4 extra ROM slots. One can have a 32K part being two ROMs in one. That socket also supports flash via a couple of jumpers. You also still have the 4 ROM sockets on the BBC motherboard. And it also has 128K byte RAM for slots 4-7 and 12-15.

Test 2. The on board latch works! This means the IO address selection and R/W decode is working well enough to produce the correct rising pulse to latch the latch. (I routed D6 and D7 to the two spare latches as test points).

It passed the first test. Memory expansion plugged in to CPU socket and CPU plugged in to the memory expander!

Next up test the latch and on motherboard ROM select decode. If that is okay then we override the on motherboard latch.

Finally swallowed hard, bit my lip, and pulled out my two Acorn A3000s to look at the battery damage. One of them is one I has had since new in 1989. The other is one I have acquired and looks newer. Anyway there was some damage but nothing really bad. Both are having the white vinegar treatment. Here’s my original after some vinegar treatment. At least they wont get worse. Gives me time to fix sort them out properly.

So progress is slow. Bleeping out shows there are no shorts and all the connections go to the right place. However I seem to have run out of turned pinned headers (needed for the stacking connector) and 16 and 28 pin IC sockets. So I have ordered a bunch of parts. However looking at it so far it should at least work for sideways rom provided I got driving the clock pin on the latch right! (Its latched on a rising pulse and the data lines are held beyond the end of the 6502’ high clock which means data is still valid when the not write goes high! Not write is inverted read not write NANDed with the clock)

My latest project, memory expansion for the BBC micro. Got to bleep it out to see where I screwed up!

So I’ve designed a replacement for the BBC micro memory expansion board I posted a little whole ago. Its somewhat simplified as it uses a single static RAM chip. It does not currently support shadow screen memory which the original one did. But that will be in the second version.

Here’s the github project!

https://github.com/CyberspiceHardware/Solidisk2Meg128K

Reverse engineering a memory add on for the old BBC Micro. It seems they cut a lot of corners!

Testing flash cartridges with my #Acorn #Electron Excuse the untidy desk!

RIFA madness!

Acorn Electron user port cartridge that will slot in to the Electron Plus 1 and similar.

https://github.com/CyberspiceHardware/ElectronUserPort

#acorn #electron #acornelectron

Decided my previous #introduction was a little brief. So here's a less brief one. Became interested in electronics as a child thanks to an uncle. Moved from that to coding in the very late 70s. Got my first computer, a BBC Micro in the early 80s and I still have it. Went off to uni and studied physics and astronomy. Had a brief sojourn in accountancy. Returned to uni and studied computing and electronic engineering. Three years as a post doc research assistant working on a gravitation wave detector. Created a distro of ARM Linux in the late 90s. Then industry developing embedded software. I'm now a tech lead. Photography, roller derby, knitting, and old computers as hobbies. Develop software and hardware for old acorn machines. #coder #EmbeddedSoftware #6502 #acorn #bbcmicro #arm #acornelectron #acornarchimedes #opensourcehardware #retrocomputing #rollerderby #astrophysics #knitting #lgbtia

Hello all. After twatter’s purchase by an evil genius billionaire and its inevitable descent further in to cess-pittery it has been suggested I come here so here I am. Leftie LGBTQ+ techy, mostly software at all levels, some hardware (generally older school), biker, knitter, model maker, roller derby player. #introduction #introductions