*** M E M O R U M ***

And it's a highly recommended read, too, Dave.

Strangely, I've been looking forward to the nights drawing in. It's been a year since I got my MTX 512 and I'm hoping now things in my home life are getting more settled, I'll be able to spend some more time with it.

Dave wrote: ↑18 Oct 2021 17:49 My take on the history of Memotech http://primrosebank.net/computers/memotech.htm, release of the MTX http://primrosebank.net/computers/mtx/mtxabout.htm and the Russian sales bid http://primrosebank.net/computers/mtx/m ... an_bid.htm can be found via the links attached

Absolutely fascinating, thank you. I've read the first two articles. Haven't time for the Russian one right now, but I'll come back to it later with great interest.

Very commendable site you've put together. Again, I'll read it all in much more detail when I have time.

RichardHallas wrote: ↑18 Oct 2021 12:14 By the way, Martin Allcorn… I don't know him personally, but his is certainly a name I've encountered in the Acorn world, and I was interested to see a familiar RISC OS icon on your page! (Indeed, I'm one of those "very few" people who'd be able to assemble your original RISC OS-based firmware code…!) I wonder if he ever subscribed to RISC User…

He did! I rcognised your name and wondered....

But it was Acorn User that published a couple of my programs.

The MTX emulator on RiscOs is, I think, on the Acorn User 200 CD, and there was a space invaders clone in 1K before that. Invaders eventually got re-written in Z80 on the MTX as Memofest Invaders, which is of course avaiable on Dave's site!

The "easy" way to get files onto the MTX is to build your own network adaptor and use FTP.http://primrosebank.net/computers/mtx/p ... fx/nfx.htm and viewtopic.php?f=17&t=478
It's all prototype stuff at the moment, but a proper board etc is on the to-do list we've given to Dave

Martin A wrote: ↑20 Oct 2021 09:43

RichardHallas wrote: ↑18 Oct 2021 12:14 By the way, Martin Allcorn… I don't know him personally, but his is certainly a name I've encountered in the Acorn world, and I was interested to see a familiar RISC OS icon on your page! (Indeed, I'm one of those "very few" people who'd be able to assemble your original RISC OS-based firmware code…!) I wonder if he ever subscribed to RISC User…

He did! I recognised your name and wondered....

Heh! Very good. Man of taste.

And yes, it's me. I'm just an amateur tinkerer again, now.

Martin A wrote: ↑20 Oct 2021 09:43 But it was Acorn User that published a couple of my programs.

You should have submitted things to the RISC User Disk. OK, the distribution would have been much smaller compared with Acorn User, but the pay was probably a fair bit better, and the disks remained available after the magazines had been published, unlike regular magazine disks that only lasted for a month.

I too had some things published by Acorn User. I wonder if you remember OmniDesk, a sort of modular desktop utility…? The nicest thing about that, for me, is that – some time later – someone at Acorn told me that it had impressed people in Acorn, and had actually inspired the new plug-in-based version of Configure that arrived with RISC OS 4.

I was always rather disappointed that no-one else ever wrote any plug-ins for OmniDesk, though, as it could have become a lot more useful with more utilities integrated. A couple of people did say they'd write plug-ins, but nothing ever happened. I subsequently slightly regretted giving it to Acorn User, because I think it suffered too much from the limited-time exposure of the monthly magazine disk.

I know BEEBUG Ltd said they wished I'd given it to them instead, and with hindsight I probably should have done. I think they'd probably have made more/better use of it. But never mind. One lives and learns.

Martin A wrote: ↑20 Oct 2021 09:43 The MTX emulator on RiscOs is, I think, on the Acorn User 200 CD, and there was a space invaders clone in 1K before that. Invaders eventually got re-written in Z80 on the MTX as Memofest Invaders, which is of course avaiable on Dave's site!

Oh, wow, you wrote that MTX emulator?! Most impressive. I hadn't realised - that'd be one reason why your name was familiar, I suppose. (Further investigation suggests you wrote other emulators too, such as ZX81 and Spectrum.)

Funnily enough, I have a copy of your emulator to hand: it's right here on my Mac, accessible under RPCEmu. (It's not long since I went looking for it and found it somewhere online.) Actually, I used to be really into emulators on RISC OS, and drew realistic-looking icons for many of them. (E.g. I created all the BBC and Spectrum icons used by 6502Em and Z80Em and associated utilities, the ones used by Speccy, a nice ZX81 for Mark Rison's emulator, an Atari ST for STem, various C64 ones for Frodo, Colecovision for ColEm, MSX for fMSX, and probably various others that I've forgotten.) Your MTX is one of the few emulated (on RISC OS) platforms that I didn't draw icons for. To be fair, I do quite like your existing icon, but if you'd wanted a fairly realistic rendition of the MTX512 as a RISC OS desktop icon in the 16-colour Wimp palette, I used to specialise in those! I'd have been happy to do one for you (still would if you wanted it). I used to take pride in getting the details accurate even in a small space; e.g. most of my icons have the correct number of keys on their keyboards…!

Anyway… unfortunately, I haven't yet got your MTX working under RPCEmu. Admittedly I haven't tried that hard, and it looks to be nearly there. It does appear to start up OK if I run it under Aemulor (so, an emulator running under 26-bit emulation on an emulator…!), but it looks as though it's attempting to use a custom screen mode when it starts up, as I get a 2×2 grid of fragmented images, rather than a single coherent screen.

I have MTX version 1.43; is there anything newer? Looking at the version history in your !RunImage, I see that it claims to use MODE 9; but MODE 9 works OK for me in RPCEmu, whereas the emulator displays a corrupted image, so I'm not sure what the problem is. I'd wondered if it needed a custom mode definition, but seemingly not… Actually, I wonder if it's something to do with Aemulor…? Unfortunately, MTX just aborts if I try to run it natively without Aemulor (unsurprisingly), so I can't see what happens to the screen 'normally'. (I just briefly tried running your Spectrum emulator under Aemulor, too, and its emulated screen was split into two half-detail copies, positioned side by side.)

By the way, I've just tried to download the copy of MTX off the primrosebank.net site to find out what version that is, but the link's broken.

Anyway, if MTX can be made to run successfully under RISC OS 5.2x on RPCEmu, I'd be very interested in having access to it…

Martin A wrote: ↑20 Oct 2021 09:43 The "easy" way to get files onto the MTX is to build your own network adaptor and use FTP.http://primrosebank.net/computers/mtx/p ... fx/nfx.htm and viewtopic.php?f=17&t=478
It's all prototype stuff at the moment, but a proper board etc is on the to-do list we've given to Dave

Well, unfortunately I have no personal experience in electronics and no suitable equipment, so I wouldn't be in a position to build one myself. (Actually, this is an area I'd like to learn about… but whether I ever have time is another question, and if I did, I'd be starting from absolute basics. And I'm not even sure where to start. So… no realistic prospect of my building anything in the foreseeable future!)

On the other hand, if you, Dave or anyone else could offer to sell me a prebuilt interface, I'd be more than happy to buy one.

!MTX is very much a 26 bit app, having started life getting the absolute maximum performance out of the ARM 2 in my old Archimedes 310. Its not at all well behaved. It did well getting as far as it did!

None of the sound modules are 32 bitted and the main emulator is very much tied to the combined PC/Flags R15. So RiscOS 4 is the end of the line without a total re-write.

There was a minor upgrade about 8 years ago to fix a load/save bug (1.44), my builds here say 1.45 but I can't for the life of remember what the difference is.

It does use mode 9, entered via VDU 22,9 and it makes no checks to see if the OS really came up with mode 9. On the Arc that was never an issue as all of them had mode 9. So if the OS provides say mode 12 or mode 15 instead it's going to produce garbage. Intollerant doesn't begin to describe it.

Andy Key's Memu and the MemiPi builds being so good, !MTX is really just a bit of history now.

OK, next question…

After initially being sent the wrong part, I've finally acquired a little ‘BNC male to Phono female’ adapter to plug into the monitor port at the back of the MTX512, as advised earlier.

However, I have to say that I'm not happy about this connector at all, simply because of the ridiculous tightness of it within the small square plastic well surrounding the BNC connector on the back of the machine. Now that I've inserted it, I can't get it out again. Hopefully that won't matter, but I don't like that situation.

Problem is, every single BNC male plug I've found (whether it's an adapter or the end of a cable) has a bayonet attachment that you have to turn and lock into position. And once it's in there and locked, there's so little room to physically grip it that it's all but impossible to remove it again.

Am I missing something? What was Memotech's original monitor cable like (assuming they used to supply one)? Is there a version with a longer 'sleeve' that protrudes further from the back, and can thus be turned to be unlocked more easily? I've had a good hunt around online and all the BNC connectors that I can find appear to have an identical design: i.e. they're all very short, and will vanish entirely within the plastic well, such that once attached they'll be all but impossible to remove again.

I'd like to be able to get an adaptor, or appropriate cable, that I can attach and subsequently remove without an excess of difficulty. Any advice?

Yes, the BNC connector is too far recessed in the plastic trim to be user friendly, but, now that you have the BNC to phono adapter fitted, why would you need to remove it? Your video cable should have a phono plug, so if you want to disconnect the cable, you'd surely just unplug the phono connector?

I struggle to get the adapters removed once fitted, so I don't even try

regards
Dave

I have a BBC Monitor lead from Maplin in the late 80s like all the others its a pain to get in and out. Since the lead had to be shared with a BBC Master I eventually settled on modding the MTX.

As the hole in the case is too big to just replace the BNC with a phono socket, I settled for piggybacking a phono socket mounted in one of the RS232 blanking plates.

With a custom internal CFX normally connected inside the MTX, it's never going to have an RS232 board fitted so that was the logical place to fit it. Plus drilling plastic is a lot easier than drilling the metal end plate.
Maybe not something you'de want to do on a "pristine" MTX? But that MTX is anything but, since over the years it's had about 1/3 of the big components replaced, but is is convenient.

Hi,

Interesting solution, Martin. I'm not sure whether that's something I'd want to do or not, but maybe – rather than damaging the plastic blanking plate – an alternative answer might be possible, such as a custom mount to locate there instead, maybe made out of wood and painted.

Anyway, it's too late now – unless I can get the adapter out again – as I didn't realise the problem until it was too late and the adapter was fitted.

Dave, I agree, it's not the end of the world by any means. However, I just don't like doing things that are irreversible, especially when they're "stupidly irreversible", like this. I don't think there's any really negative consequence to adding one of these adaptors, unless it makes it extra-difficult to disassemble the machine.

I haven't yet looked inside the MTX – just haven't had time to do anything with it yet – but I do intend to examine its internals, and although I can't imagine why I'd want to take the motherboard out of the base, if that ever proved necessary for some reason, I'm not sure what consequences the presence of the adapter might have. If the BNC socket should in theory unscrew from the case on the inside, and then withdraw backwards through the hole in the plastic… well, the presence of the adapter is presumably going to prevent that from happening, so it'd need to be unsoldered, I imagine. Maybe I'm imagining difficulties that either don't exist or will never arise, but… as I say, I just don't like things that can be put in but never be taken out again.

I have to say, I really wonder what Memotech was thinking here – especially in such an otherwise beautifully designed machine. Why fit a connector that's impossible to disconnect?! The choice seems to be either to do what we've done, and insert an adapter that permanently changes the socket from BNC to phono, or plug in an actual BNC cable and then discover – too late! – that it's attached to the machine for all time! If only Memotech had designed the machine to use a phono plug in the first place – or, at least, found a way to make the BNC socket stick out further, so that the bayonet part wasn't recessed beyond where you can reach it – this whole situation could have been avoided.

Taking the system, apart won't be affected by the adaptor.

Once the end plates are removed the Keyboard cable can be unplugged and the top half slides off. That's probably the worst part of the process over with, the cable isn't the strongest thing in the world and at 2 inches wide the connector can be a bit stiff.

The motherboard should then be held in by one bolt from the bottom of the case to one of the regulators. The PCB and plasic moulding then slide out. The PCB sits in a slot at the front and on a lip at the back. He moulding has lugs that fit in the same hole as the lower rear endplate screws, as that runs full length.

The grey 4 way cable in the photo plugs onto the video board, for a non RS232 MTX that connection will be the only thing left connecting the mouding to the motherboard. If you've got an RS232 there will be 2 more connections to unplug. The video BNC and Audio phono don't need removing.

With everything separated it you feel the need to remove BNC adaptor it sould be easy(ish) as you'll have access from the bottom, the plastic only forms 3 sides of the "box". Not quite as simple as a RiscPc to disassemble, but close. One screwdriver and one allen key are the only tools needed.