Memotech MTX Series 3 for next years Memofest ?????

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lezanderson
Posts: 186
Joined: 14 Aug 2012 15:31

Memotech MTX Series 3 for next years Memofest ?????

Post by lezanderson »

Lets be more forward looking....

How about desiging a NEW Memotech ... MTX S3 or RS128 PLUS !! Something for next years MEMOFEST !

I was recently looking at doing a feasability study for what it would cost ICs etc to build a Memotech MTX S3 or RS128 +. This was the conclusions

Outline: Must be SBC Single Board Computer :Must use easily sourced ICs, must be cheap, must be relatively easy to build, :

Draft Spec:

HD64180 or Z80 CPU ?
128K fast SRAM
512K NVSRAM Silicon Disc ?
128K/256 EEPROM
Z80 DART RS232 ? HD64180 has serial ports build into chip
Z80 CTC
GAL PLD memory decoder
EPM7128SLC84 Glue logic
V9958+DRAMs Video
YM2149 + SN76489 Sound
8255 for CF Card
MCU to read keyboard
etc etc ..

ICs should cost abouit $30 (£20) So ideally it could be made for £50 per unit ????

It won't obviously be 100% compatible with the original but that would be very hard to achieve.

I could supply the ICs for free plus other bits and bobs to keep costs down.. enough to make TEN prototypes... We could even send one to Geoff Boyd ??....but who would like to design and build it ??


Well it's just a though.... sort of Brainstorming !!

Lez
Martin A
Posts: 799
Joined: 09 Nov 2013 21:03

Re: Memotech MTX Series 3 for next years Memofest ?????

Post by Martin A »

Dave and I have been looking at something similar:

Essentially get the MTX+ working on the backplane over 3 or 4 boards. Then once that's working then maybe try and compress everything on to one board for the "MTY".

The PCB starts getting relatively expensive though once you move up to 200 x 160, which should fit the rails in the MTX case and be around 2/3 of the size of the MTX board. That's $99.00 plus taxes and delivery for 5, 2 layer boards at Itead's current rate. Fitting the components onto anything much smaller would be a chore on a 2 layer board (150x160 would be $80+)

It's seems do-able, and certainly for less than the £315 I paid for my first MTX.

For the MTX+ see Dave's site http://www.primrosebank.net/computers/m ... txplus.htm

So far we've got a working Video board, working real time clock access.

I've got a provisional design for 512k battery backed ram, though that needs a lot of work.

And of course we've started brainstorming the CPU board
lezanderson
Posts: 186
Joined: 14 Aug 2012 15:31

Re: Memotech MTX Series 3 for next years Memofest ?????

Post by lezanderson »

My Very Generic spec would be based on minimum chip count and costing :

the HD64180 : probably 8 or 10 MHz .. 6800 or Z80 BUS 'R or Z' ?? These are Cheap, which I like !

It has the following features:

Memory Management Unit (MMU) which supports 512k bytes of memory, and 64k bytes I/O space
12 new instructions were added
Two channel Direct Memory Access Controller (DMAC)
Programmable wait state generator
Programmable DRAM refresh
Two channel Asynchronous Serial Communication Interface (ASCI)
Two channel 16-bit Programmable Reload Timer (PRT)
1-channel Clocked Serial I/O Port (CSI/O)
Programmable Vectored Interrupt Controller

I believe it uses 3 clock cycles average per insctruction rather than 4 in the standard Z80

comes in DIP64 same as V9958

The R type: 6800 Bus could be easily interfaced to ICs like 6522,6821, 6850 ethernet etc ?? So very flexible..

This would need quite a few changes to the MTXs OS !!

As much Glue logic as humanly possible squeezed into a CPLD .. EPM7128 or EPM7160 again to reduce chip count !

Memory decoding using a GAL PLD and HD64180 memory managment unit ??
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