[MAME] Emulating the MTX

Pernod
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Re: [MAME] Emulating the MTX

Post by Pernod »

Martin A wrote: 16 May 2022 23:52 Not masses you can do with it, but yes Fuzix will boot to the VDP
Looks like it was detecting a CFX-II by reading 00 from port 60, now fixed to read FF from unmapped ports.
0011.png
0011.png (3.71 KiB) Viewed 338 times
- Nigel

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Bill B
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Re: [MAME] Emulating the MTX

Post by Bill B »

In practice. reading an unimplemented port usually returns whatever value was last on the data bus.

If the port read is using an IN A,(ADDR) instruction, then that is the second byte of the opcode, i.e. the address of the port to read.

There are a few places in the CFX-II ROM which rely upon this behaviour. Possibly also other code.
Pernod
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Re: [MAME] Emulating the MTX

Post by Pernod »

Bill B wrote: 17 May 2022 09:13 In practice. reading an unimplemented port usually returns whatever value was last on the data bus.

If the port read is using an IN A,(ADDR) instruction, then that is the second byte of the opcode, i.e. the address of the port to read.

There are a few places in the CFX-II ROM which rely upon this behaviour. Possibly also other code.
Thanks, good to know.
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Pernod
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Re: [MAME] Emulating the MTX

Post by Pernod »

Martin A wrote: 16 May 2022 23:52 Not masses you can do with it, but yes Fuzix will boot to the VDP
Interesting to see you have 784K RAM in there, and is reported correctly by Fuzix. What does CFX report on real hardware with 784K? My emulation reports only 32K.

If I run with something like 512K then CFX reports the correct amount, but Fuzix loses 16K reporting 496K.

Are these discrepancies expected or do I have a mapping issue?
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Martin A
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Re: [MAME] Emulating the MTX

Post by Martin A »

CFX just reports a value based on LTSPG in the system variables, so it's whatever the boot memory check finds.

The ram board that's usually in my MTX has 2 x 512k chips on it. Limitations in the MTX's paging system mean that parts of that are not available.

The mapper makes 15 full 32k pages available in basic, plus the 16k half page, and the 16k fixed for 512k so that's what CFX reports. That's probably the same in MAME.

In CPM mode the pages are 48k in size (as there's no rom) and the mapper makes 16 of them available, add the 16k fixed and that's 784k.

I'd hazard a guess that Fuzix reports (or needs) full 48k pages. 512k total ram might well mean MAME sets up CPM mode as 10 full and 1 part page, plus the 16k fixed.

Ignoring the part page, 10 x 48k + 16k would explain the 496k reported
Pernod
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Re: [MAME] Emulating the MTX

Post by Pernod »

Martin A wrote: 19 May 2022 14:00 Ignoring the part page, 10 x 48k + 16k would explain the 496k reported
Thanks, makes sense.

I think I'm done with this round of MTX improvements, they'll be available in next week's MAME release.

I'll probably take a look at the CFX-II in the coming weeks, for the 80 column functionality.

There's still the question of why the Videowall ROMs at http://www.primrosebank.net/computers/m ... 12roms.htm are password protected, someone must know? If I can get them in MAME at least they won't be lost, and can implement what is currently known about the hardware.
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Dave
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Re: [MAME] Emulating the MTX

Post by Dave »

There is little point in emulating the MTX control ROMs, the MTX computer was just an interface to a really complex piece of non-computer hardware, making extensive use of analogue and digital electronics for video frame capture and manipulation. Unless you are going to emulate that, there is no point in doing the MTX VW ROMs. You could emulate the control software "demo" mode, but I really see little benefit in doing that.

http://primrosebank.net/computers/mtx/v ... l_ddfs.htm

(The ROMs are password protected because I made them so, if you were desperate to know why, you could have emailed me vie the webmaster address. I saw little point in publishing the MTX VideoWall ROMs without also publishing the FrameStore ROMs. The VideoWall hardware was market leading at the time, and whilst now obsolete, I suspect that the original copyright owner would be reluctant to release it into the public domain. I **may** open the archive at some point in the future, but that would depend on my getting permission from Geoff.)
Pernod
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Re: [MAME] Emulating the MTX

Post by Pernod »

Dave wrote: 19 May 2022 15:12 There is little point in emulating the MTX control ROMs, the MTX computer was just an interface to a really complex piece of non-computer hardware, making extensive use of analogue and digital electronics for video frame capture and manipulation. Unless you are going to emulate that, there is no point in doing the MTX VW ROMs. You could emulate the control software "demo" mode, but I really see little benefit in doing that.
MAME already emulates various capture devices such as scanners and video digitisers, by feeding the emulation JPG or AVI files, so there's little reason why something useful couldn't be emulated with this. We also easily manage multiple video outputs that can be arranged as a wall. So would be great to try to bring this obscure hardware back to life via emulation at some point.
Dave wrote: 19 May 2022 15:12 (The ROMs are password protected because I made them so, if you were desperate to know why, you could have emailed me vie the webmaster address.
Sorry, didn't even consider the email option as I knew you were here.
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Martin A
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Re: [MAME] Emulating the MTX

Post by Martin A »

Pernod wrote: 19 May 2022 16:19 MAME already emulates various capture devices such as scanners and video digitisers, by feeding the emulation JPG or AVI files, so there's little reason why something useful couldn't be emulated with this. We also easily manage multiple video outputs that can be arranged as a wall. So would be great to try to bring this obscure hardware back to life via emulation at some point.
Andy has some info here http://www.nyangau.org/vgavw/vgavw.htm on the video wall. The MTX was only a tiny part of the videowall hardware.
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