MTX512 reports only 32K RAM

stephen_usher · Post by **stephen_usher** » 23 Jan 2017 20:29

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?

Dave · Post by **Dave** » 23 Jan 2017 21:10

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 · Post by **stephen_usher** » 23 Jan 2017 21:21

Bother! Only 3732s.

lezanderson · Post by **lezanderson** » 27 Jan 2017 12:24

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 · Post by **stephen_usher** » 29 Jan 2017 11:55

I've read that... scary amount of desoldering involved. (I've been talking to Dave via e-mail after buying the CFX from him.)

1024MAK · Post by **1024MAK** » 29 Jan 2017 12:09

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

, if you want more details, ask).

Mark

stephen_usher · Post by **stephen_usher** » 29 Jan 2017 16:36

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.

1024MAK · Post by **1024MAK** » 29 Jan 2017 22:28

Pictures once it's all fitted please

Mark

stephen_usher · Post by **stephen_usher** » 16 Mar 2017 00:38

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

Thank-you Dave and Andy!

Here's Dave's page about this with more pictures: http://primrosebank.net/computers/mtx/p ... pecial.htm

Dave · Post by **Dave** » 16 Mar 2017 01:07

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

"I just love it when a plan comes together"

* M E M O R U M *

MTX512 reports only 32K RAM

MTX512 reports only 32K RAM

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