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steve3000

My guess would be IC14. Oh, I hope you're right... because I suspected IC14 was dodgy back in 2016, when the computer wouldn't start up at all. So I socketed it at the time, but swapping it made no difference (turned out to be a memory fault in lower 16kb), so I think I placed the original back in!...

steve3000

cmorley wrote: ↑
Wed Nov 21, 2018 12:01 am
I have something similar on a B. Mode 7 is perfect so I assume it is the ULA... I haven't investgated it yet.

I thought the ULA too and it was first thing I swapped... Now I'm scratching my head over what circuitry could possibly be specific to MODE4 and MODE6. Something timing related perhaps?

steve3000

I have a graphics glitch problem on my Issue 3 beeb. It's very odd, and very specific to two screen modes only - MODE 4 and MODE 6. I get red or sometimes green dots (never blue) all over the background. The dots are not static - they rapidly appear/disappear all the time. I never see a mix of both ...

steve3000

Without a circuit diagram it's going to be difficult to know for sure unless you try. Until mine stopped working, I'd been working on the assumption the US beeb is part-way between an issue 7 beeb and a B+... Still no circuit diagram, but I have found some interesting documentation about the US bee...

steve3000

Still not fixed my US Beeb... However, I was recently forwarded some scans of a 9-page document about how to prepare re-imported US spec BBC computers back to UK spec. Great to see some original documentation mentioning some of the differences between the UK and US spec. Shame there is no circuit di...

steve3000

Does anyone know the specs of the original fan Acorn put in, such as CFM? The base A310 did not come with a fan, but it was part of the harddisc upgrade (along with backplane and hdd podule). I don't know what the CFM was, but the MFM HDD pumped out a lot of heat, so needed the fan... as I recall t...

steve3000

On a 0.1" grid, the pins from one chip occupy the same space as another row of pins from another rom. True... but is there a way round this by careful design, because are not all pins are required from each ROM? E.g. the data lines are needed for all ROMs but address lines could just be taken from ...

steve3000

This sounds like a great project! Could the bare PCB be designed with holes positioned for either A5000 or other Archies? So you just need to design one PCB and keep option for A5000 users to fit the header pins to the correct holes...

steve3000

This demo was not so good as Chock Away. The plane image was rather crude but it was animated so it looked fantastic in 1991. Maybe I should rephrase my question. Can anybody recall a demo like this which was on discs supplied with a computer? I remember we used an Archimedes without HDD and 8 MHz ...

steve3000

It works fine on RISC OS 2 and MEMC1A, I still use it occasionally on my A3000. :) The problem was with RISC OS 3, not MEMC1A. The ROM chips that RISC OS 3 was supplied on typically could not operate at the faster speed, so the machine crashed when old RO2 developed BASIC programmes called this unde...

steve3000

Try https://uk.rs-online.com/web/p/heatsinks/1899025/ Or https://uk.farnell.com/fischer-elektronik/ick-24-b/heat-sink-dip-glue-on-13-c-w/dp/4620914 Mark I have some of those that Mark has linked to. They work fine :) Paul Brilliant find, thanks guys! I'll be passing an RS trade counter later this w...

steve3000

Ok, I'm a bit stuck. For various reasons (mainly repairs and pcb cleaning) I've had my main beeb in bits for the past couple of months, but finally got round to putting it all back together today. However, somewhere along the line I've misplaced the Video ULA heatsink... Looked everywhere but I can'...

steve3000

sirbod wrote: ↑
Sun Oct 28, 2018 11:50 am
You can't do that as it would change the code from:

Quite right Jon, sounded good as a concept, but the problem is clear when you see the code written out...

I like your idea!

steve3000

It was pointed out to me offline, by another eagle eyed coder, that you can save another instruction if you remove "add r8,r7,r7" and reverse the two compares, using shifted r7. E.g. for the first use: "cmp r4,r7,lsl#1" then reverse the conditions for the next instructions... "addlt r7,r7,r4" etc. A...

steve3000

litwr wrote: ↑
Sat Oct 27, 2018 7:51 pm
However I can't figure out how to improve dx>0 and dy >0 tests.

Replace

Code: Select all

adds r3,r3,0   ;dx > 0
mvnmi r9,-1    ;sx = -1
movpl r9,1     ;sx = 1
rsbmi r3,r3,0  ;dx = abs(dx)

With

Code: Select all

movs r9,r3,asr 32
movpl r9,1
rsbmi r3,r3,0

Think that'll do it?

steve3000

The Acorn Archimedes line unfortunately never seems to have made it into Germany Welcome! The Archimedes did make it to Germany - I recall there was a German version of the A3000 and possibly A3020? The German version of the operating system, RISC OS 3.19, was also sold as an upgrade for all Archim...

steve3000

An extension of Daniel's option 1 above: if the games are not available on JASPP, you could use !ADFFS to image your original discs yourself, and then use !ADFFS to run the images from your HDD.

steve3000

Interesting, and certainly some optimizations possible in the ARM code (straight off: replace "BEQ exit" by "LDMEQFD R13!..." and I suspect the dx>0 and dy>0 tests can be improved by 1 instruction each with a bit of tinkering). But isn't this missing the point? Each ARM instruction is 32bit, so will...

steve3000

You're probably fine if you're using a recent version of FPE, but as long as the FPEmulator doesn't have an 'E' in its version number (*help fpemulator) then it should support hardware FPA. You will also need to turn on the FPA test in !Si, if that's what you're using, or it will not even look for i...

steve3000

AndyMc1280 wrote: ↑
Wed Sep 26, 2018 11:55 am
Haven't had chance to use it in anger as there's no battery. My "jet plane" comment was regarding the noise of the Fan and HDD

Lol! It is fast too though

steve3000

The Alpha variant of the A5000 had, IIRC, a 16 MHz system bus (and hence memory) clock. It needed "special" MEMC1a that worked at that speed, and I think I remember a lot of discussions about "matched" MEMC1a to get it working reliably. On the other hand, Chris' Acorn tells me that the Alpha varian...

steve3000

Dead (or not) MEMC should be easy to test if you have a chip extractor tool and A5000a with MEMC socket... that said, they can be a pain to remove unless the tool is fully engaged. I'd test these first as the logic is going to be tougher to test.

steve3000

Dear God it is like a jet plane. :shock: Silent fan mod and CF card in its future.... Nine one Andy, they are fast aren't they! The 66mhz oscillator is socketed too, and they overclock nicely ;) 8mb boards are fiddly in the A5000, if anything isn't pushed in fully or is a bit loose, it'll drop back...

steve3000

Would that same type of fan work on an A310 as well? Thanks I think I posted on here about my A540 silent fan conversion (but struggle to find this thread from my phone). The A540 has two fans, these are each the same size as the A5000's fan, and I can recommend the fans I used (which look awfully ...

steve3000

So, inspired by this thread, I started checking the power on reset circuitry. For me, C68 was saying 'no capacitance' when I tested with my capacitor tester. Ahhh, thanks for sharing! I've still not got back to my dead A5000, but it sounds like you had exactly the same symptoms! I had even looked a...

steve3000

This Archimedes classic recently appeared on Android:

https://play.google.com/store/apps/deta ... Cataclysmm

steve3000

As Rob says, RISC OS 3.7 and later require a mode definition file installed in your !Boot sequence to provide anything other than the minimal VGA compatible screen modes such as 640x480. The mode definition file provides RISC OS with the video timings for each screen mode resolution supported by you...

steve3000

I suspect many "US converted back to UK" beebs are actually just German ones. Not sure this is correct, although the differences are small between these. US beeb PCBs were always fully populated and included the US speech chips, whereas German beebs were not typically sold fully populated and didn'...

steve3000

Nice pictures :) but just a bit too dark to see all the links, any chance next time you have it open, you could take a photo of the whole PCB with all the links visible? I'm struggling to find anywhere with a picture of a US beeb PCB that clearly show the link settings... My US beeb kind-of works bu...

steve3000

Hi, I'm trying to find a copy of Xenon 2 hopefully in ADF format. I've scoured the net to no avail. Does anyone know where I can obtain it please? I've not looked for this, but would have thought it should be readily available, at least the 1997 re-release, as this was given away on an Acorn User c...

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Search found 1903 matches

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Re: Puzzling graphics glitch on my Beeb

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