To get the board to work (as 128K) you need to plug 74LS244s into the 2 big sockets, and resistor packs into RP2 and RP3. The resistor packs need to be 10 pins each with 5 individual 47 Ohm resistors. To make it work as 512K you will need one of the little decoder boards or piggyback a 74LS253 on one of the existing chips. I don't know if the MacMemory upgrade required cutting any traces on the mobo. If it did, they will have to be jumpered. You do have the original 64K ROMs, so that's why you're stuck at 512K.

As for restoring the board to original condition, I wouldn't attempt it. It's already been through one severe heat cycle to unsolder the original RAM, and doing it again without special equipment is very likely to lift traces or pull out plate-through connections. You're better off as suggested to keep an eye open for a 128K board that hasn't been messed with, though those are getting hard to find. Everybody upgraded their Macs because a Mac with only 128K of RAM is nearly useless. With 128K the OS is forced to swap out program segments to the 400K floppy, and it is SLOW! There is also a problem finding old RAM chips. You'll have to rob them from other old equipment, maybe a PC/AT RAM expansion card, if you can find one with the right chips in sockets.

You know the board has been upgraded, but it's hidden inside the box. Nobody else will know unless you tell them.

With 128K the OS is forced to swap out program segments to the 400K floppy, and it is SLOW!

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It's my understanding that the SegmentLoader only read program segments FROM the floppy disk, and didn't write them back to the disk. Is that true?

I have to say that it will be a lot of work to get that board back to original condition or at least functionally original. The missing chips will have to be found and if the RAM on the board is more than 128k and is soldered, then all those chips will have to be de-soldered and 64x1 chips soldered in their place. I found a place that has the chips for $1.20 each but they have a 25 chip minimum order.

All that being said, finding an unmolested 128k motherboard isn't all that easy either. If you just want a functional compact Mac, then you would be better to get a 512k or 512ke motherboard until you can manage to get your hands on a 128k motherboard. The 128k is a very hot model with collectors at the moment so competition for restoration and repair parts is high. I managed to get one recently that, fortunately, only needs minimal repair to get working again or else I'd need to spend more on parts than it's worth.

It's my understanding that the SegmentLoader only read program segments FROM the floppy disk, and didn't write them back to the disk. Is that true?

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Usually so. Program segments ought not to be modified, so are read-only. Data segments are written to disk as needed.

Have you ever gotten in the dread floppy-swappy cycle where you have to swap a couple of floppies in and out of the drive 20 or 30 times to get a program launched? Floppies are a last resort for virtual memory, but Macs often need more than 128K, -32K for display, -10K system heap, -stack space, = very little working room.

If you just want a functional compact Mac, then you would be better to get a 512k or 512ke motherboard until you can manage to get your hands on a 128k motherboard. The 128k is a very hot model with collectors at the moment so competition for restoration and repair parts is high.

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He already has 512K on the board. The chips he needs to replace are incredibly easy to come by. Read the associated posts. It may work as a 128K without a decoder in place at location E3, once he bridges any severed traces.

Besides It already works as a 512K with the expansion RAM board he already has, which obviously decodes the additional RAM, so no need to go looking for another one.

And I still don't understand all this "rare" and "hot model" stuff. It is neither. The 128K has always commanded prices from $150 to $1500 or more, depending on condition and accessories, for the last decade as long as I have been monitoring. The 128K will always command a premium because serious collectors and amateurs alike are like lemmings rushing toward the cliff face to throw their hard earned cash over for a shot at a sensationalized collectable.

Also, non-working boards show up all the time around the internet, on eBay, Craigslist, LowEnd Mac swap and sometimes here. All the parts he needs can be cannibalized from a non-working 512K board as well, which sell for considerably less (working or not). In fact, I have about a half-dozen non-functional 128K boards in storage for parts and to restore, I think I paid $15 for all of them. Patience is a virtue.

Anonymous Freak – check this out regarding 128K SIMMs.

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D-OH! :I

Obviously I was wrong on the capacity of the individual SIMMs, but I was also wrong on the number of said SIMMs, and on the unit involved.

I have a group of 8 (not 2) that are collectively labeled "128 MB for SE/30-IIci"

I knew for certain I had some 30-pin SIMMs labeled "128". I was just way off on the remembered meaning therein.