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RobC wrote: ↑

Fri Jan 11, 2019 10:06 pm

I think the two halves of an 8MB SIMM have separate RAS signals

Yes, that's what I understood was the case for 8mb SIMMs as they are dual-ranked...but I will be reading up a bit more thoroughly on the subject before making any plans

RobC wrote: ↑

Fri Jan 11, 2019 4:08 pm

I believe that the 4MB upgrade in my A3000 might well be the SIMM type so I could possibly put in an 8MB SIMM and just wire across the extra address line

I'm thinking of trying exactly the same, once can work out the required signals needed to patch across. Will keep you posted.

Makes sense...so there should only be a handful of signals needed between the 8mb RAM and twin MEMC board? In which case, if you could replace the 4mb RAM in the A3000's 4mb upgrade with 8mb, then wire across the necessary signals (including the extra address line) to a twin MEMC board, you could av...

Well, looking at an A3000 last night, there is actually more height clearance under the keyboard than I thought there was. So I think you could get enough height, either but directly mounting the converter pcb to the motherboard or the 4-8mb ROM card to the converter. However I'm now thinking it's t...

Still need to desolder the original MEMC1A from the A3000 PCB and fit a socket but I managed to remove the ARM2 and add an ARM3 upgrade. Also need to consider the clearance - you'll need to fit the A5000 expansion under the A3000 keyboard, and it'll have to avoid other components. Might just be pos...

Great work!

Brilliant! I look forward to reading more as/when you wrote up

Can't help with a spare mobo unfortunately, but interested how you cleaned up the battery damage - looks like you've take the tracks back to copper? And nice closeup picture - what's that taken with? My mezzanine A3010 has terrible battery damage, but after manually rewiring about 15 tracks, it boot...

Never managed it, but not tried much. RISC OS 2 doesn't support IDE without external hardware, so I assumed no support for HDD under RO2 - unless there is a podule emulation of IDE, or ST506 HDD emulation?

myelin wrote: ↑

Tue Jan 08, 2019 1:46 am

so I now have all the classic OS images working

Great! Does RO3.19 work ok too? (No reason it shouldn't, but it is a but different, and the final official RISC OS release that ran pre-RiscPC)

Another option would be to see if I can allow the host machine to switch banks, so it can access the whole 16MB (maybe with a fixed 1-2MB and a paging area above that). I like the sound of this, especially if you could do a keyboard scan at startup and respond to say f1, f2, f3, f4 pressed, by sele...

WOW! Well done! =D> Really great to see how you have developed this. How does the ROM switching work (or is this work in progress?). For Arthur, I found 0.3 to be the most challenging to get working, because as you've noticed, it doesn't support >1mb. For Arthur 1.2, as I recall, this worked in my A...

Thanks for the recommendations, I'll definitely go for lead solder then! Arc would have been leaded. CPC sell multicore 60-40 still, that's what I've found to be the best? I have a US brand too which doesn't wet as well... I use no-clean liquid flux The multicore 60-40, 0.7mm from CPC looks good and...

I'm almost out of solder and wondering what people recommend for retro-computer work. My last 100g reel of lead-free came from my local Maplin store, so I need alternatives... I'm planning to do some SMD removal (to replace dead IOC from my A4 and a dead VIDC from my old A5000) and some extensive re...

Not replaced the socket yet, but after (accidentally) leaving the computer running all day today, while I was at work - I noticed the glitch is not restricted to MODEs 4 and 6! Seems all >2 colour modes are affected except MODE 7. Selecting background COLOUR 129 in MODE 1 or MODE 5, then typing CLS ...

I'm sharing a few of my hardware drivers for some of the rarer hardware. In return, I'd dearly love a driver to add to the collection for the soundcard Ace RiscBlaster that I've recently purchased from ebay. Great effort Paul, thanks for sharing these - it highlights that we definitely need an arch...

Update - still not solved but continued incremental improvements. This weekend I de-soldered all PCB power connectors, removed, cleaned and refitted. I spotted that the central 0v connector had a hairline fracture so I replaced this. I also re-soldered the ULA socket in case of dry joints, but I did...

Has anyone else observed this, or better still, fixed this? Something looks wrong there with the amount of flex in your key... My A310 keyboard (next to me at the moment) doesn't behave quite like this - the left shift does flex slightly, but even when pressed at the far right of the left key, it s...

91 ohms! :shock: Humm... re-measured and I get 18 ohms. Can't figure out how I previously measured 91... but that's what I'd noted down. IIRC, issue 3 and earlier boards did not link the three different +5V/Vcc supply networks together, while issue 4 and issue 7 boards do link them. Seems correct, ...

The resistor is the big one next to the video ULA. As in the biggest resistor on that part of the PCB. Dooh! Typical. I overlook the most enormous resistor... Anyhow, it measures a nice round 18.0 ohms. :) Voltage measured at pin 15 is 2.04v. Resistance from pin 15 to the power connector is 91 ohms...

Well it's not solved yet but as of today, I can run Elite happily for hours with no interference present, providing the lid is off the computer (this was not the case when I started this thread). However, shortly after placing the lid back over the computer, the interference begins to appear as the ...

Is the video ULA socket the original or has it been replaced? As well as the item/points raised above, also check / test the following: S26 link and it’s connections, R114 (18 ohms), diodes D16, D17 and D18, C47 (10uF), Plus all their connections. And the voltage at ULA pin 15. Is the 16MHz clock w...

I finally re-found this excellent Xmas music mix for the Beeb from 1990, which I vividly recall annoying my parents with by playing repeatedly BITD. Since coming back to the beeb a few years ago I'd searched on and off for this demo, but had no idea what it was called or how/where I came across it, ...

Although I've tracked the glitch down to the ULA, I haven't solved the problem yet... After fitting a modern heatsink to the ULA, using a sensible amount of thermal paste, the computer runs Elite nicely for a good 20 minutes with the lid on...but then the interference still appears! :( Even with the...

Good advice Mark. For modern components designed to use heatsink you only need the thinnest amount of thermal paste to cover any microscopic imperfections on the IC surface and heatsink surface (on a modern CPU and heatsink this will typically be < 0.1mm film of paste) to avoid the paste becoming a ...

After a break, I've come back to my beeb with the graphics glitch, and tonight I think I've pinpointed the cause of the glitch... In your case, I wonder if the Video ULA is over-heating as well. Is the heatsink loose? Although I'd refitted the heatsink, using new thermal compound and confirmed the h...

RISC OS on RPi does exactly this on a SD card, by having a DOSFS image drive present in the ADFS map (inside the !Boot directory), which is physically mapped to a real DOS partition. So if you wrote the 2Gb RISC OS 5 SD image to a CF card this would probably achieve what you want, providing you were...

You'll be fitting it, to a BBC I presume? I'll be fitting this to my main beeb over Christmas, providing I can fix the ongoing interference issue with the beeb... @steve3000 could you post a ROM dump and scan of the manual please [-o< Certainly can. Will be in a week or so as away from home now. :)

That turned out to be the confluence of three things: 1 - slightly loose motherboard power spade connectors 2 - poor connection to Video ULA 3 - lowish power supply voltage (~4.65V) As Ed mentioned earlier, the fix was to clean/tighten the spade connectors (which helped a bit) and then fit a turned...

Wow! That's wonderful to see on the beeb!