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Interesting. I’ll take a look and see if maybe I can add a second row of headers for those address signals. The BGA parts are an interesting tradeoff. They’re easier for me to assemble than hundreds of 0.5mm pitch TQFP pins (wider pitch and easier reflow) but less easily sourced and harder for other...

Could you add some pins to the top end of ROM 4 (e.g. Pins 1-4), just for mechanical support, as the usb connector will be near there? Updated images (and design files) are up at https://github.com/google/myelin-acorn-electron-hardware/tree/master/a3000_rom_emulator -- see anything else obviously m...

DutchAcorn wrote: ↑

Wed Dec 05, 2018 10:34 pm

myelin wrote: ↑

Wed Dec 05, 2018 9:01 pm

I'm interested in a Risc PC!

Sorry myelin, markdryan was first to claim!

Hehe... I could only try!

IanS wrote: ↑

Wed Dec 05, 2018 7:40 pm

Could you add some pins to the top end of ROM 4 (e.g. Pins 1-4), just for mechanical support, as the usb connector will be near there?

Good idea! I'll do that.

I'm interested in a Risc PC!

Making some progress here! This is the most complicated board I've designed, by quite a long way. I managed to use all 117 signals on the CPLD, and daisy chaining 25 address/control lines through two BGA flash chips was an interesting process! Hopefully this will solder OK :) Here are some renders o...

You'll need a terminator somewhere in the circuit. Technically you should have one at each end, but for a short cable run (a few metres) it won't matter. The Econet terminator also biases the circuit, so it sits in the reset (data=1) state. Without one, I believe you'll end up with a 'line jammed' e...

I'm interested in one 8-bit V3b with DOM (as long as it'll work in an A3000), shipped to Mountain View, CA.

I could possibly handle the A5000/A3000 pin overlap by using a few more pins on the CPLD and making it redefine them as appropriate... I’ll figure that out when I do the PCB layout. That said, it looks like there might be enough interest in an A5000 version that I could just make another PCB with pi...

Those pics are perfect; thank you Ian! Looks like I’ll need to consider component clearance for the A3xx and A4xx when working out the board shape here. I need to look more carefully, but it looks like the podule backplane might block off the side of the board that was where I was planning on puttin...

The spacing of the roms on the A5000 is definately different to the A3000, from online pics, it looks like the A3xx spacing is similar to the A3000. I can't find any good close up top-down shots of A5000 motherboards, but it looks like they're a bit closer together than those on the A3000 - is that...

The fitting instructions for the carrier board show you need to pick up LA18, LA19, and LA20 from IC28. Odd... Looks like the A310 has LA18 connected; LK12 lets you connect it to pin 2 or pin 24 of the ROMs, like LK17+LK18 on the A3000: http://www.drobe.co.uk/archives/ftp.acorn.com/documents/CIRCUI...

It would be nice to make the connections a bit configurable, so it could be fitted to an A3xx without ROM carrier board (the carrier board picks up a few address lines that aren't available as standard on the rom sockets). Ah, excellent... glad I asked for feedback, because I'd completely overlooke...

I've finally figured out a design I'm happy with for this -- posting here to see if anyone else would be interested in one. This will be a board that plugs in to the four ROM sockets on an A3000, and act like a DualOS/MultiOS board, plus let you flash new versions of RISC OS (or old versions... so y...

After acquiring my first Electron less than a month ago I set out to design a bit of hardware to bung in the back of it. Working on the old principle of walking before you run, I decided on a very simple one-socket sideways ROM card. At the weekend I got the board up and running and was pleased to ...

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?

Excellent... I think I can make this work. I'm trying to do it with a single 16-bit wide flash chip, and do two accesses per host access. Luckily the flash chip I'm looking at (S29GL064N) has a compatible page mode; the first access takes 90ns and subsequent accesses within a 16-byte page take 25ns....

It looks like MEMC has a single-cycle ROM access mode for sequential accesses, "200ns with 60ns nibble-mode", configured by setting bits 7:6 (for high ROM) or 5:4 (for low ROM) of the MEMC Control Register to '11'. This is documented in section 6.5 of the MEMC datasheet (0460,019, 1986). This has be...

I’m looking to capture 96 channels at 8MHz; will these options work for that? Most of my concept is the front end: plugging into the A3000 board and multiplexing 96 channels down to 16 is all the custom part of it does. If the BBB can receive 16 bit data at 48MHz and send it out over Ethernet, it wo...

Yep! I haven't watched the video yet, but will almost certainly want to use his libcyprio code if it can work in isochronous mode or provide buffers for me to write into. It looks like the Domesday Duplicator buffers a bit of data in the FPGA , which I won't be able to do with a CPLD, so I may not b...

I've been trying to bring three A3000 motherboards to life, with no luck so far. One is still in need of some capacitors, and the other two were severely battery damaged (ROM sockets missing half their pins -- that sort of thing!). For the battery damaged two, I've replaced the ROM sockets and CMOS ...

Looks like I never made a bill of materials for this project! C1-3 are 100nF, C4-5 are 1uF. The regulator is an MCP1700T-3302E/MB. I buy everything from Digi-Key here in the US; with any luck they’re reasonably available where you are! Let me know if you need any more info. Programming the CPLD will...

If that's how you choose to interpret it, then I guess it's up to you. Seems you read the first two sentences you quoted but not the third - which clearly (I thought) explained that it was a different focus. I think that wasn't as clear from your last post. I took your "retro OS" comment from one o...

This thread! I keep half-writing comments and then going away, only to return to find someone else has made my point much more eloquently! I'm really glad that there are people who think RISC OS has enough value that they're prepared to put their time and money into tracking down and buying out righ...

Permissive vs copyleft debate aside, can I just say how awesome it is that they've actually gone back and relicensed everything right from the beginning of time in the repository? Terrible source control faux pas, but legally it's amazing: it probably means we can build an open source RISC OS 3.60 R...

This looks amazing and I would love to give it a try! However, something seems to be wrong with maemagel.com; it's just serving a blank homepage and 404 for all the links here.

Progress update: it now reads frames from the Econet, verifies the CRC, and dumps them to the USB serial port. Time to start seeing if I can integrate Gareth's ArduinoFilestore.

You don't hndle scout frames, you handle scout... um... transactions. See Econet over IP and [url=http://beebwiki.mdfs.net/Econet_packet]Econet packet[url]. I see... so if one were to build an Econet-to-AUN bridge, the trick would be to immediately acknowledge every scout frame coming in from the E...

As far as GPL vs Apache goes, my take is that they're more interested in making RISC OS super convenient to embed and aren't too bothered by the idea of closed-source forks. There's plenty of examples out there of successful projects with healthy ecosystems and lots of contributors that are under BS...

Indeed... it would be amazing to get the source code to Arthur or RISC OS 2/3, but having at least one version under an open source license makes me happy

They're apparently talking to 3QD as well, so more free stuff may be forthcoming, fingers crossed!