Panasonic MSX2+ internal ram upgrade

Rookie (18)

01-06-2019, 10:17

So I recently got my hands on a Panasonic FS-A1FX. What I hadn't noticed however was the low amount of Ram it featured so I figured I could upgrade it.

Sure enough, I didn't need to search for a long time in order to find two guides. https://www.oboroc.com/posts/2004/05/09/panasonic-msx2plus-c...
http://www.msxarchive.nl/pub/msx/docs/hwmodsetc/msxa1wsxmemo...

They are written by the same guy but do contain some minor differences. However that's not really the important part, but rather one particular description/instruction that I need a little bit of help with.

He describes the following:
"Look for the T9769 chip (MSX engine) of the other side of PCB. Next to it you will
find two jumpers: J3 and J2 (R140 and R141 for WSX PCB). Desolder resistor from
J2 (R140 on WSX). Short J3 (R141) with a small piece of wire to get +5V on T9769
pin 52. "

The jumpers he mention are easy to find, however on my computer J2 does not have a resistor. Instead there's just a trace between the points. Correct me if I'm wrong, but since I can't remove a non-existent resistor, the solution would just be to cut the trace in order to achieve the same result. If I ever need to reverse the modification it would be easy to add a jumper wire, just like I've already done with J3.

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Par RetroTechie

Paragon (1563)

01-06-2019, 20:06

Welcome here, Macross_VF1!

Macross_VF1 wrote:

Would think so too. Seems like you've got it under control, what is it you need help with?

Par Macross_VF1

Rookie (18)

01-06-2019, 20:23

RetroTechie wrote:

Welcome here, Macross_VF1!

Macross_VF1 wrote:

Would think so too. Seems like you've got it under control, what is it you need help with?

I just wanted confirmation that I wasn't about to reduce my computer to a pile of molten slag.

Par Macross_VF1

Rookie (18)

02-06-2019, 22:04

I can now completely confirm that the guide/s linked to above work perfectly with the small caveat that the trace between J2 should be cut, instead of a resistor removed.

Par sdsnatcher73

Prophet (3953)

03-06-2019, 06:26

Great job. The resistor may only be present on the later WSX model.

Par dhau

Paragon (1570)

05-06-2019, 00:54

Thanks for this info! I never seen an FX, but I got 2 WSX and one WX. If it's not too late, can you please share photos of your mod? Specifically the trace you cut.

Par Macross_VF1

Rookie (18)

05-06-2019, 18:44

dhau wrote:

Thanks for this info! I never seen an FX, but I got 2 WSX and one WX. If it's not too late, can you please share photos of your mod? Specifically the trace you cut.

Aw, now I have to open it up all again. Think of all the time I could have spent playing some games instead.

Seriously though, here are some pictures.

As you can see I've installed sockets for the chips while I was at it. As for cutting the trace, I just used a hobby knife and scored the trace until I no longer got a connection between the two points using a multimeter in continuity mode.

This was a rather easy mod. I suspect the most difficult part for most people will be removing the old chips, though if you have the proper tools, particularly a soldering iron with a vaccum pump, it's a piece of cake.

Par tvalenca

Paladin (747)

06-06-2019, 15:12

Actually, the most difficult on this mod is if you make it a 512k mod: You'll have to mess with 2 pins from T9769 MSX Engine and pull a wire from a third pin to connect the second 44256 bank. (And you may want to sold these UNDER the board, because piggybacking the RAM chips over the socket will most likely prevent keyboard going back to it's place.

EDIT: FOUND! It was like ***this*** on a A1WX that i used to have.

Par Grauw

Ascended (10768)

06-06-2019, 15:31

Macross_VF1 wrote:

Sure enough, I didn't need to search for a long time in order to find two guides.
https://www.oboroc.com/posts/2004/05/09/panasonic-msx2plus-c...

Adrian Oboroc wrote:

2. Clifer, a korean MSX fan, made similar mod using 1MByte DRAM chip from 72-pin PC SIMM. His instruction is more comprehensive, since it actually explains what the mod does, not just the steps on doing it. ~~http://myhome.naver.com/clifer98/menu2.html~~

If anyone’s interested, that struck through page in the update notes there can still be found on the Internet Archive’s Wayback Machine, though a few of the images are missing:

http://web.archive.org/web/20080224122956/http://myhome.nave...

Par shaneo

Supporter (5)

09-11-2020, 08:32

Just wondering does any sell these chips or can link me to these chips for a 512k ram upgrade