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The Memotech MTX Series


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Memofest 2016 was hosted at my home in Aberdeen on 29th/30th October

(The Memofest 2016 preparation page is archived here)

Despite my initial worries that people would find making the trip to Aberdeen a bit too much to contemplate, the turnout was surprisingly good, with most of "the usual suspects" (Andy, Bill, Claus, Mark & Paul), as well as Martin, making the trip - thanks everyone for making the effort! Jim joined us by Skype for most of the afternoon session too (before the iPad battery gave out).

Although I had tried to plan some structure for the day and developed a tentative schedule for the activities, unsurprisingly, the day turned out to be pretty much "free form", the main activities are described below.

Andy has also written up the event on his webpage and supplied most of the photos that I have used here (thanks Andy)

Mark has also written up some notes on Memorum (the Memotech Forum)

Exhibits on display 

A selection of my original Memotech hardware was on display, including :-

  •  MTX512S2 attached to the "New" style SDX with integral single 3.5" disk drive
  • "Old" style SDX with modified PC HD 3.5" disk drives, reconfigured as Memotech Type 07
  • MTX512 attached to an FDX with modified PC HD 3.5" disk drives, reconfigured as Memotech Type 07
  • MTX2000 (disconnected from Video Wall system)
  • MTX512S2 attached to a 4x4 Video Wall system (driving a single TV monitor)
  • Various other MTX500/512 computers
  • Various other Video Wall hardware
A selection of my modern day, MTX related, hardware was on display, including :-  
  • MTX512 attached to MAGROM, CFX, or REMEMOrizer
  • MTX PI (a Raspberry Pi running MEMU inside an original MTX case
  • MTXPlus+ Prototype

On his page, Andy has referred to my place as being "basically a Memotech lab" which made me smile - Nicola (my wife) has other ways of referring to my Memotech stuff though :-)

Somewhere under the kit you see below lies what used to be the dining room table!

Some of my Memotech kit that was on display for the event.
My 4x4 Video Wall hardware, connected to the MTX512S2 that came with the hotchpotch of Video Wall kit that I obtained in 2013.

In this photo you can also see the prototype Video board and Z180 CPU board from MTXPlus+ as well as one of the replacement PSUs that Mark had built for Claus and I.

(Photo courtesy of Andy)
In this photo you can see the video upscaler and switch box that I use to display the 80 column TTL RGB output from my FDX or SDX on a VGA monitor.

They are sat on the MTX2000 system unit with its associated keyboard in front. In the foreground is my MTX512S2 and "new" style SDX disk drive.

(Photo courtesy of Andy)
To the right of those is my original FDX, upgraded with replacement 3.5" disk drives and a PC power supply

A second FDX is buried under the two MTX PSUs, "old" style SDX disk controller with a pair of 3.5" floppy drives and a collection 3.5" SDX/FDX diskettes.

(Photo courtesy of Andy)
Andy demoed his REMEMOTECH r2, upgraded to include enhanced floating point support to allow it to outperform a 25Mhz Z180 MTXPlus+ when plotting the Mandelbrot set - achieving a time of 82s!

In "real world" applications, the Z180 MTXPlus+ still wins though :-)

Here you can see the startup screen after REMEMOTECH has booted CP/M from the SD card.

Further details of the REMEMOTECH demo on Andy's site
Andy's REMEMOTECH in close up.

(Photo courtesy of Andy) 
Bill demoed his new hardware add-on for the MTX. Bill had been a fan of CFX, but not of the 56 column screen limitation (based on Andy's SCPM ROM) imposed on it by the MTX Video hardware. 

Bill has designed and built an 80 column board that emulates (and exceeds the capabilities of) the original Memotech 80 column board and built his own prototype PCB.

(Photo courtesy of Andy) 
Solder side of Bill's home etched PCB.

The main components (Parallax Propeller, serial EEPROM, voltage regulator) are available for around 10. See here for the technical details of Bill's board.

(Photo courtesy of Andy) 
Sample output from Bill's 80 column board, mimicking the fonts of the original 80 column board and showing the improved range of 64 colours available with Bill's board.

(Photo courtesy of Andy) 
Another sample of the output from Bill's 80 column board - the photos do not do the board justice, the quality of the output is really very good. Everyone was most impressed by Bill's efforts and agreed that it would be an ideal companion to CFX.

(Martin and Dave are likely to "borrow" Bill's work (with permission) and look to add the functionality to an improved CFX board.)

(Photo courtesy of Andy) 
Martin and I demoed MTXPlus+, our MTX compatible "super computer".

The setup you see here includes the first versions of the "production PCBs for the backplane and video board, along with the prototype Z80 CPU, I/O and 6502 co-processor boards.

(Photo courtesy of Andy) 
Martin demoed the 6502 co-processor running BBC 6502 BASIC.

More details about the 6502 co-processor board

(Photo courtesy of Andy) 
The demo included showing MTXPlus+ displaying a number of the loading screens from Sinclair ZX Spectrum games.

Tony Brewer is helping us to implement a much enhanced version of Speculator on the system. This is currently a "work in progress", but I think that we (well, Tony really) are almost there.
Andy demoed his new game for MTX - HEX-TRAIN, a Train Simulator - with a difference.

The "game has animated 3D solid graphics at 192x128, in 15 colours, at 16 frames per second" - all done on a 4Mhz Z80 !

Read the full details of how this is possible on Andy's dedicated page. - go on, read it - you will be in awe !
Of course, the Memotech community must take credit for "encouraging" Andy to improve the 3D graphics he offered with Turbo - HEX-TRAIN is obviously the result of that - albeit that it has taken 30+ years to get there !   
Seriously though, needless to say, everyone was very impressed with the performance of the game and the huge amount of work that Andy has put in to the developing the "engine" that makes this impressive performance possible.
Here you can see the "magic" behind the demo - I am talking about Andy's magic coding fingers - rather than the game engine!

After the game demo, Andy tried to explain the complexities of HEX-TRAIN to the mere mortals in the room by showing us the internal workings of the 3d model and the "difference engine" used to allow such complex graphics to be drawn by a 4MHz Z80 CPU!
The HEX-TRAIN world!

Every possible route through the system is modeled and stored in the game data file
Part of the 3d model inside HEX-TRAIN

My brief notes here do not come anywhere close to doing justice to this great piece of work - as I said  - get over to Andy's page and read the full details.
I was a little disappointed to find that HEX-TRAIN has problems on MTXPlus+. I would like to understand why that is, and hopefully, do something about it.

HEX-TRAIN is optimised for the TMS-9929 VDP and there may be subtle differences in the V9958 timing that are enough to break the program - further investigation required.
As is usual on these occasions, a Memotech themed cake was provided - this year's offering is shown here.  

(Photo courtesy of Andy) 
Despite the attractions of the cake - you can see that the majority of the attendees are engrossed in Andy's explanation of the inner workings of HEX-TRAIN. However, I can confirm that little persuasion was required to drag them into the kitchen to attack the cake!

Andy further demonstrated his extensive range of skills by ably wielding the cake knife and the group then proceeded to regale Nicola and Julie with MTX related anecdotes over tea & cake. (I will let you make your own mind up on whether the "regaling" was appreciated or not!). Some time was also taken to provide counseling to Andy to help him cope with his return to Southampton's answer to Imelda Marcos on Sunday morning.
Having made short work of his cake . . . . .

Bill then demoed the enhancements that he has made to MEMU, including the ability to load games from .wav files.

(Photo courtesy of Andy) 

After CakeFest, Paul demoed the latest version of his MTX game development engine, showing off some of the impressive sound and graphics capabilities that the tool allows to be integrated into games for the MTX.

(Photo courtesy of Andy)  

It would be really interesting to see and hear a game for the MTX that took full advantage of these impressive tools.

The group is looking forward to seeing and hearing such a game from Paul at Memofest 2017!

Paul - make it so please :-)

(Photo courtesy of Andy)
Claus demoed his "new" game conversion  - C-So!, originally released by Sega for the SG-1000 video game console in 1985.

The title screen from C-So!, complete with Memofest 2016 banner ! 
C-So! is a platform type game - with SeeSaws   
Claus demonstrating his gaming skills on C-So!

The MTX keyboard that Claus is using to play the game is attached to my  MTXPlus+ prototype that is running the game.
Unfortunately, Bill had already left when I found time to demo MEMU-Pi, a Raspberry Pi running inside a real MTX case running a version of MEMU that Bill had modified for me.

The MTX keyboard is wired to the Pi GPIO pins and Bill has patched the keyboard routines in MEMU to read the MTX keyboard through the GPIO pins.
I have made a small, reversible, change to the keyboard to allow the two unmarked keys to be separately sensed.

The unmarked key on the right hand side is used to invoke the MEMU-Pi menu.
The usual "Memotech Hospital" was planned, but there was little call on its services. The only patient booked in in advance was the video board from Paul's MTX.

Paul couldn't bring the whole MTX to Aberdeen, so brought the Video daughter board on the basis that it had failed previously (but had already been repaired by Mark). However, testing showed that the Video board was fine and there must be another fault on the machine now. 
Despite only having one monitor connected to the output, and a problem with the MTX512S2 that was connected to it (see below), I, or rather Andy, was able to demonstrate operation of the Video Wall hardware.

In this photo, the Video Wall prompt monitor output is being fed to the Decoder/Distribution Amplifier (DDA) input.
The MTX512S2 that we were using to control the Video Wall electronics came from my other collection of Video Wall hardware.

It appears that the DDFS units in the Video Wall are of an older vintage than the S2 and do not support some of the features, e.g., Colour Wash, configured in the S2 software. Despite this, Andy was able to show the system running some of the video sequences stored in the S2 ROM.
With the TV/monitor plugged into the appropriate DDFS output, you can see that this is the top left corner of the input signal being magnified by the DDFS and output to the (very small) Video Wall.

(Photo courtesy of Andy)
The prompt monitor display when a Video Wall sequence is running   
Another section of the tiled display   
Another section of the tiled display    
Another section of the tiled display    
I was aware of a problem with the MTX512S2 attached to my Video Wall system, after about 20 minutes, the picture would lose colour, then a little later, would break up completely. The machine was running very hot - particularly around the power input capacitor and I suspected that one of the voltage regulators was faulty, but I had not had time to find/fix the problem before Memofest.

During the Video Wall demo, using copious amounts of freezer spray (ably applied by Mark), were were able to narrow the problem down to the LM7812 (+12VDC regulator).
A wider angle view of Mark delving inside the Video Wall MTX512S2

As you can see, working on retro computers can be thirsty work! 
The die-hards (Mark, Martin & I) resumed on Sunday morning, refreshed after the extra hour in bed courtesy of the DST change, we were able to spend another whole day on geek speak!

Claus and Andy were both flying back home on Sunday morning, but they met for breakfast out at their airport hotel before they flew. To help Claus get his body clock back in sync, it was very considerate of Andy to forgo the extra hour in bed and join Claus for breakfast at Swedish time :-)
A selection of my other Memotech computers were on display, including the 4 you see here. (The one missing its keyboard on top of the toolbox is my original MTX512 - the keyboard is currently being used on MTXPlus+ ).

On Sunday, we proved that the other three you see here are all working fine, including the MTX-500 with the German keyboard that I received from Manfred Flume recently and modified to use a Cisco DC only power supply.
Mark obviously enjoyed his visit to Scotland and took the opportunity to see a little more of the UK on his way home to Bristol!   
As in previous years, despite the intention of having a game High Score competition, we got sidetracked and didn't actually manage to fit in enough time for the competition - maybe next time . . . . . .  




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