MTX512 reports only 32K RAM

About original Memotech hardware.
stephen_usher
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Joined: 27 Nov 2016 19:58

MTX512 reports only 32K RAM

Post by stephen_usher »

OK, now I have a working MTX512 but I discovered that it only thinks that it has 32K RAM after plugging in a CFX board.

This is a surprise given that all the links on the circuit board are correct for a 64K machine.

PRINT PEEK(64122) returns 0, so the machine certainly thinks that it's an MTX500.

Could the machine somehow have the wrong PAL fitted, or can some other fault make it think that it only has 32K RAM?
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Dave
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Re: MTX512 reports only 32K RAM

Post by Dave »

Has it definitely 64k of RAM fitted ?

Many "MTX512s" have only 32k on the system board and needed the other 32k to be on a RAM card.

The RAMs should be OKI 3764's for 64k

regards
Dave
stephen_usher
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Joined: 27 Nov 2016 19:58

Re: MTX512 reports only 32K RAM

Post by stephen_usher »

Bother! Only 3732s. :-(
lezanderson
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Joined: 14 Aug 2012 15:31

Re: MTX512 reports only 32K RAM

Post by lezanderson »

There's a section on Dave's Website on how to upgrade an MTX500 to 64K ...?

http://www.primrosebank.net/computers/m ... epairs.htm
stephen_usher
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Joined: 27 Nov 2016 19:58

Re: MTX512 reports only 32K RAM

Post by stephen_usher »

I've read that... scary amount of desoldering involved. (I've been talking to Dave via e-mail after buying the CFX from him.)
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1024MAK
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Location: Looking forward to summer, in Somerset, UK

Re: MTX512 reports only 32K RAM

Post by 1024MAK »

It's a must to visit Dave's site ;)
Andy may be able to sell you one of his modern RAM expansion boards (fully built), this uses a modern SRAM chip and plugs into the edge connector, so no soldering needed. If you need links, shout out.

If you do want to upgrade the on board RAM, because of the amount of desoldering, it's best to use a desoldering iron, or hot air. Some "DIY" electric paint stripper hot air "guns" work as well (it's what I use :D, if you want more details, ask).

Mark
:!: Standby alert :!:
“There are four lights!”
Step up to red alert. Sir, are you absolutely sure? It does mean changing the bulb :!:
Looking forward to summer in Somerset later in the year :D

Not as many MTXs as Dave! :lol:
stephen_usher
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Joined: 27 Nov 2016 19:58

Re: MTX512 reports only 32K RAM

Post by stephen_usher »

Dave's offered to get and modify one of Andy's boards to pass through the ROM select lines and add DIN 41612 connectors to daisy-chain the memory and CFX boards together so that they can both fit internally (with the CF card to IDE device will be external, on the end of a ribbon cable).

I've taken him up on his offer. It looks like a very neat solution to the problem.
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1024MAK
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Location: Looking forward to summer, in Somerset, UK

Re: MTX512 reports only 32K RAM

Post by 1024MAK »

Pictures once it's all fitted please ;)

Mark
:!: Standby alert :!:
“There are four lights!”
Step up to red alert. Sir, are you absolutely sure? It does mean changing the bulb :!:
Looking forward to summer in Somerset later in the year :D

Not as many MTXs as Dave! :lol:
stephen_usher
Posts: 325
Joined: 27 Nov 2016 19:58

Re: MTX512 reports only 32K RAM

Post by stephen_usher »

Well Dave's parcel arrived today, and...

Image

Thank-you Dave and Andy!

Here's Dave's page about this with more pictures: http://primrosebank.net/computers/mtx/p ... pecial.htm
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Dave
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Re: MTX512 reports only 32K RAM

Post by Dave »

And I'll be adding that picture to the page too . . . .

"I just love it when a plan comes together" :D
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