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FS-A1 RAM upgrade

By ApolloBoy

Expert (96)

ApolloBoy's picture

06-06-2013, 10:22

Is it possible to upgrade the main RAM in the FS-A1 to at least 128K? I'd like to use MSX-DOS2 and FAT16 partitions with my MegaFlashROM SCC+ SD but I can't use either with just 64K. I don't have my FS-A1 in front of me right now, but I'm fairly certain it has the S1985 chip which would help facilitate a RAM upgrade.

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By Jipe

Paragon (1631)

Jipe's picture

06-06-2013, 10:55

look at : http://usbsecretbase.michikusa.jp/

By luppie

Paladin (869)

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06-06-2013, 12:08

Add 2 x 41464 memory IC's on the place IC14 & IC16
Add 2 x 100nF ceramic capacitors on place C49 & C51

You're done Big smile

By msxholder

Champion (399)

msxholder's picture

06-06-2013, 17:29

There is a difference between A1,A1f and A1fm or A1 mark II

By Jipe

Paragon (1631)

Jipe's picture

06-06-2013, 19:11

A1FM http://usbsecretbase.michikusa.jp/a1fm/ram.html

A1F http://usbsecretbase.michikusa.jp/a1f/ram.html

By ApolloBoy

Expert (96)

ApolloBoy's picture

06-06-2013, 20:28

I have an original FS-A1 so none of those methods will work. I have it opened up in front of me right now and it does indeed have the S1985, so that's a start.

By msxholder

Champion (399)

msxholder's picture

06-06-2013, 20:52

Short and simple use the schematics of the hb9
two 74ls32 and one inverter 74ls04 for decoding
we and oe with ma16
Greetings
m6000a-0108fp-646102 gate array-
For combining slotselects subom ,mainrom etc

By ApolloBoy

Expert (96)

ApolloBoy's picture

06-06-2013, 21:27

msxholder wrote:

Short and simple use the schematics of the hb9
two 74ls32 and one inverter 74ls04 for decoding
we and oe with ma16
Greetings
m6000a-0108fp-646102 gate array-
For combining slotselects subom ,mainrom etc

???

By ApolloBoy

Expert (96)

ApolloBoy's picture

08-06-2013, 20:10

Anyone else care to chime in? If it's not that feasible to upgrade my FS-A1 I might just pick up an FS-A1WSX and upgrade that instead.

By syn

Prophet (2146)

syn's picture

10-06-2013, 13:23

msxholder wrote:

use the schematics of the hb9

Do you mean this? http://bas-ditta.info/verkoopenlinks/doehetzelf/geheugenuitb...

By RetroTechie

Paragon (1563)

RetroTechie's picture

18-01-2017, 01:05

ApolloBoy wrote:

I have it opened up in front of me right now and it does indeed have the S1985, so that's a start.

Forget 128 KB, this machine should be -relatively- easy to upgrade to 256 or 512KB using a single static RAM chip.

Main RAM would have to be removed, you'd have to find a ROM or empty ROM socket to put the SRAM onto, and may require soldering directly to some S1985 pins... Eek! Don't know if there's a ready-to-follow description out there.

But in my humble opinion: either you wouldn't need to ask this question, or it's a no-go.