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.

Cyberspice boosted

> On Thursday, NHTSA said it had discovered in 16 separate instances when this occurred that Autopilot “aborted vehicle control less than one second prior to the first impact,” suggesting the driver was not prepared to assume full control over the vehicle.

> CEO Elon Musk has often claimed that accidents cannot be the fault of the company, as data it extracted invariably showed Autopilot was not active in the moment of the collision.

Sigh. 🤦‍♀️

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)

Show thread
Cyberspice boosted

RT @Public_Citizen
Pride corporate sponsors bankrolling anti-LGBTQ politicians:

Toyota: $601,500

AT&T: $297,990

Comcast: $121,350

State Farm: $79,550

Fedex: $67,000

Amazon: $62,500

General Motors: $48,500

Budweiser: $42,250

Enterprise: $41,300

Walmart: $24,500

Corporate Pride is a sham.

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

Cyberspice boosted

US billionaires buy up Hawaii while most of us Hawaiians don't "own" a single acre of our US-illegally occupied home. Mark Zuckerberg forced us from his 1200 acre ranch on Kaua'i. Elon's buddy Larry Ellison owns an entire island, while we remain homeless.

Cyberspice boosted

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.

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

Cyberspice boosted

Sure would suck if you spent $44,000,000,000 on a website thinking that people would keep looking at that website and then people stopped looking at that website and went and looked at a different website instead

Decided my previous 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. #6502

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.

Show older
OldBytes Space - Mastodon

The social network of the future: No ads, no corporate surveillance, ethical design, and decentralization! Own your data with Mastodon!