>I collect home micros, and I recently acquired a Mac 128K. However, it's
>been quite heavily modified with contemporary third-party add-ons. It's
>been taken up to 1M RAM and it's had a SCSI interface installed.
Cool!
>The memory has been taken up to 512K by removing the 64K x 1 bit RAM chips
>and replacing them with 256K x 1 bit chips, plus adding a few discrete
>components (not hard, considering the 128K and 512K Macs shared the same PC
>board). It has then been taken up to 1M by adding a third-party 512K RAM
>expansion board, which plugs into one of the RAM sockets (the chip it
>displaces being installed onto the expansion board), and is connected to
>the address decoding by several flying leads.
A most interesting upgrade, I have several of those liittle add-on boards
to allow that upgrade. Not sure what to do with them, though. Just waiting
for a bunch of 128K's to come my way, I guess...
>The SCSI interface has been installed by removing the ROM chips, plugging a
>daughterboard into the empty ROM sockets, and plugging the ROM chips into
>the daughterboard. The SCSI socket replaces the cover over the battery in
>the back of the Mac.
Also very interesting. I've never quite figured them out.
>So, my question is, should I:
>1) Leave it as it is;
Definitley, unless(or until) it stops working, and then you have the fun
job of figuring out which one is bad...
>2) Remove the SCSI interface (easy, just remove the daughter board, take the
> ROM chips out of it and put them back into the motherboard's ROM sockets);
The SCSI is far too useful to remove unless broken...
>3) Remove the SCSI interface *and* the 512K RAM daughter board (not *too*
>hard,
> desolder the flying leads (taking note of where they go to, just in case I
> want to reinstall the board), remove the board from the RAM chip's socket,
> remove the RAM chip from the daughterboard and put it back in the
> motherboard's now-empty RAM socket);
Same as before for the SCSI part, and that extra RAM is very useful unless
you have some VERY old Mac software sitting around(getting a 512K running
isn't too hard, but the 128K in stock config is ALMOST useless)
>4) Take it back to original condition (quite difficult, as well as
> steps 1)and 2) it involves desoldering 16 256K x 1 bit RAM chips, (plus
> a few discrete components) and soldering in 16 64K x 1 bit RAM chips).
Too hard, and unless you have some very nice, expensive equipment to help,
it is more likely you will damage the board and/or chips. Don't forget to
remove the extra logic chip...
I have two or three 512K logic boards with similair upgrades, and I have
what seems like millions of flyback transformers, disposable 3M static
wrist straps and KillyClip(?? I don't remember what it's called. But I have
tons of parts for them... a buncha empty PCB's, a bunch of clips... no
complete ones, though) type stuff. Very strange collection of parts, all
stuffed away in boxes, still waiting to be sorted.
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Received on Thu Apr 02 1998 - 17:17:28 BST