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Ian has done a bunch of testing and the results have convinced me to order the issue 3 PCBs. They should be here early December.

I shouldn't have changed the buffer part between the prototype and issue 2. I wanted to make them easier to make.

The black stuff is carbon. It will stick to that & make a connection. WHere you've worn through to bare plastic you can roughen the surface a little to help the paint stick. It is fragile after application so you may need to re-apply if you insert/remove the flexi. I have one of these: https://uk.rs...

IanS has my original buffered test board with 11 individual buffers. I redrew the board (again) to match this test board which runs on my A3000 fine. This is the last option I am going to try...

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Yes please, full weekend.
Chris

Nickel paint, patience and great care.

Is there any chance this could be caused by old decoupling capacitors on the MEMC or on RamFVCC, and it's not really your boards' fault but more that Ian's computer needs some new capacitors? There must be a bit of variance between Ian's and my A3000 but his machine works with other expansions. The...

The curse continues. I built some boards and brought them to ABUG but they don't work in Ian's computer.

I have one idea left... if that doesn't work on Ian's computer then I don't know what else to do really.

Gosh, no interest in a twin drive? I'll put it on eBay at some point then or I might keep this one.

Hey gang, unfortunately not going to be able to make this now :( Hopefully someone else can use my space. Real world obligations need attention! :( Shame, I was going to quiz you about setting up a couple of gotek's, I guess I'll have to put in a bit of effort and read the web pages. I have goteks ...

No chance of building these up. After 3 days Mouser still haven't shipped my order for the buffer ICs. No idea why.

Update: PCBs are here :) I'll build some up this weekend to test. Appeal: I will bring some to the ABUG 9-12th Nov. If anyone who is coming to that has an A3000 and prepared to run some tests that would be appreciated - especially if you have a different model than issue 3. Both Ian and I have issue...

Update: I got a message from the PCB company. Batch 1 take #2 are in the post!

It is a capacitor. 33nF.

The S is the tolerance -20%/+50%.

For any Diptrace users on here... the title says it all really!

I've installed it and played a little. The new routing features aren't a killer but the number of formats for schematic and board it imports have increased greatly. v3.2 was a good step & v3.3 is worth installing I think.

Chris

Issue 2 sent off for manufacture. Wow this has been a time vacuum for something which should have been straight forward! This one has buffers on all the MEMC lines (optional ones on the 4xCAS which I don't need). So if this doesn't work check the For Sale forum for an A3000 with boot prints on. :lol...

RAS, A0-9 are all out of TTL spec on my machine. The four CAS look better. So basically almost everything that comes from the MEMC is dodgy! RAS, A3 & A8 were the worst IIRC - out of spec with no memory card fitted i.e. stock machine. It is all high frequncy synchronous rubbish - if you turn on BW l...

There is good news and bad news. The good news is my experiments have yielded success and I can tame the out of spec TTL DRAM signals in the A3000. The test card has the most sensitive RAM on I've found and works fine it seems. The bad news is this means a redesign of the board to add a load of schm...

I grafted the Wiki CRC (with a minor change to preserve the Y register) and 76800 is reliable to the Beeb with full CRC calculated between byte receives. 7.5kB/s or so using the original B hardware & an FTDI RS232 adapter. I think that is pretty good! I wonder though & perhaps JGH knows... I used th...

Ian and I have been running a lot of tests and the cap mod seems to have fixed the issue. The cap mod just acts as a low pass filter & filters out some of the runt pulses coming from the A3000. We have repeatability between my and Ian's A3000s so the test results are genuine. My test copies 190MB an...

Yes the SRAM is 32K and forms the lower priority 2 slots and the socket on top is the higher priority 2 slots when the 4 ghost slots are decoded. The left most socket in a BBC is the lowest priority ROM 12 The right most is the highest priority ROM 15 So fully decoded: left most socket is 0 4 8 12, ...

Hmm... there doesn't seem to be a way to get my Boobib SWR to ever be higher priority than the DFS ROM. I've got it in the furthest right socket, but DFS still takes priority. Wonder if this is due to the "ghost" ROMs being higher up? The ROMs are enumerated from 15 down to 0. So it is really the l...

I don't think that is possible in BBC BASIC. I think it whacks the state (FOR stack etc) if you STOP or END. I'd be fascinated to know if there is a work around (or my memory is false!). Variables remain intact.

Endnote: Jonathan's 'Recover' program was started at around 13:30, yesterday. It was still running this morning - I was warned! It looks like it searches for Directory entries - sector by sector. Last time I looked it was on sector 9Dxxx :shock: I'll probbly stop this later this morning . . . Is th...

Progress! I am very confident I've found the root cause of the occasional errors that IanS discovered. I've also tested a fix which I am confident has cured it. I will modify a board and send that to IanS for further testing as I only have a sample size of one A3000. It took me a while to find with ...

Does that mean that add-in boards implement the address decoding fully - for example, the Boobip RAM appears at slots 2 and 6, with no ghosting? Yes. On my RAM the small chip underneath does the decoding logic and the large chip is the RAM chip. The socket is decoded too so you could fit a 32KB ROM...

Exactly what Martin said. RTool locks the RAM, so it can't be corrupted, by default when programming. MMFS SRAM version needs to be able to write to itself - so make sure you use the unlock command in RTool. It will then list as "SRAM U" for unlocked. Some ROMs try to detect if they are running in R...

Investigations are still ongoing. I'll post when I have an update. I need to solder wires and take lots of measurements with the scope. :S

Sorry for the delay everyone but I really want to get to the root cause before I take payments and post out boards. My dev board works flawlessly! :S

The test that threw up some errors was a large file IDE->IDE copy using the desktop with NEXT slid to max. Comparing the results was sloow so I managed to get C working on arculator and wrote a noddy compare tool (attached). Works on RiscOS 3.11 - dunno about other versions. Attachment is an ADF dis...

I investigated the problem and reflowed the RAM on those boards and now they work fully. I don't think I failed to solder any pins (lead free solder :-& ) but instead think maybe I hadn't baked them properly after cleaning and there was moisture trapped under the chips on some of the boards. Either ...

IanS has a board and is testing it. He's experiencing an issue I can't replicate here. Edit: I may have replicated it Another tester would be helpful - someone who is a bit of an expert, has an IanS IDE interface and knows their way around the system, doing an md5 etc. Voulunteer? Please PM me. Once...