How do you know if its the orginal Macintosh M0001 model?

[H3NRY]

What is the possibility that the mobo RAM chips were not upgraded to 512K?

It is possible, but since it was much more common to upgrade the motherboard than to add a daughterboard, the mobo was nearly always upgraded first. The guys at MacMemory started out doing 512K upgrades, and later made a larger version of the Beck-Tech add-on that held 1MB. Note also that MacMemory made an attempt to accommodate 18-pin 1Mb RAM chips, which would have made the add-on hold 4MB. Unfortunately, I believe their guess as to the pinout of future 1Mb chips was wrong, so it never happened, and of course Apple's architecture limited RAM to 4MB max anyway. That didn't stop MacMemory from advertising "Upgrade to 4.5MB RAM!"

I can't remember whether 1.5MB RAM is one of Apple's configs supported in the Plus ROMs. I know they support powers of 2 (128K, 256K, 512K, 1MB, 2MB, 4MB). Anybody have an example of an odd memory config working?

 

[Anonymous Freak]

I recall the Plus supported 256KB SIMMs and 1 MB SIMMs, in any combination of pairs. So 2x256 (which would be strange, since it's lower than it shipped with,) 4x256, 2x1MB, 2x256+2x1MB, 4x1MB.

 

[H3NRY]

2x256+2x1MB,

Of course, that's 2.5MB! :I

 

[Anonymous Freak]

The SE/30, with its eight banks, could do 1.5 MB, as 4x256 and 4x128, although I don't think 128s were officially supported, and were exceedingly rare. (I think I have two of them, I suppose I could try them on my Plus or SE...)

 

[Mac128]

Agree with H3NRY. Almost all upgrade cards required 512K on the motherboard. However, correct me if I'm wrong H3NRY, a few bypassed the logic board altogether? It would be the exception if yours did this.

Anonymous Freak, are you saying you have 128K SIMMS? So you could have a Plus with only 256K RAM? Now that would be an experiment worth trying, eh Bunsen? I do seem to recall back there somewhere when I was looking to do this, being told that the Mac is not wired to support odd RAM configurations.

 

[Anonymous Freak]

I have no idea if the 128K SIMMs work with any Mac. I suppose I could try, though. At worst, it'll beep at me. (I could try it in pair with a couple known-size SIMMs, it would be funny to have a 768KB Plus. )

 

[giolicious]

...After you remove the RAM board, make sure you adjust the voltages which will fluctuate after removing the draw of the expansion board.

...

How do I adjust the voltages? sorry for asking im not that expert but i can do it if you let me know how.

 

[Mac128]

I believe this details the procedure:

http://68kmla.org/files/classicmac2.pdf

I have no idea if the 128K SIMMs work with any Mac.

Now if only you had 64K SIMMs. Then the Mac Plus could be every Compact Mac from the 128Ke, 512Ke through the Plus. There is some speculation that the 64K ROMs also work in the Plus. I believe it is Tom Lee who once reported he put 64K ROMs in a Plus and powered it on before he realized his mistake. So he did not confirm how well it ran in that condition. I have some spare 64K ROMs from dead boards, I should give it a go. Surely it couldn't damage anything?

 

[H3NRY]

I have some spare 64K ROMs from dead boards, I should give it a go. Surely it couldn't damage anything?

It ought to be safe. The 64K ROMs will only recognize 512K of RAM and won't initialize the SCSI port, but it should be safe, ie. no smoke. It was common to have Fat Macs with added RAM and SCSI upgrades, and they were essentially Plusses with 64K ROMs. The only fly in the ointment might be that the ROMs would be writing the screen at the wrong address, so you might not get video.

 

[giolicious]

Your Mac shows 512K because it has the original 64K ROMs most likely. You actually have 1.5MB of RAM installed, it looks like. The mobo RAM chips have probably been replaced upgrading it to 512K and there's 1 MB on the MacMemory upgrade board. If you can find the original software that came with the upgrade, it will let you set up a 1 MB RAMdisk and copy the system & Finder to it. Speeds things up nicely. The other option is to obtain a pair of ROMs from a Mac Plus or 512Ke and install them. They will let you directly address the whole amount of installed RAM. To check whether the mobo is upgraded, check the 16 identical chips under the front edge of the upgrade. If they are labeled something...4164...something, you have 128K. If they are ...41256... you have 512K on the mobo itself.
Apple's original 64K ROMs didn't support more than 512K of memory. The Plus ROMs support up to 4MB of RAM.

In any case, you have a pretty rare early Mac with an early upgrade. Congrats!

It looks like you're right H3NRY.

Here's the mobo after removing the MacMemory RAM board:

and here's the MacMemory RAM board:

Now as you can see from the pictures, there are two chips missing/removed from the mobo. My question is, can i still start(power on) this mac without the MacMemory RAM board?

Does anyone knows where can I get those missing chips and original 128k RAM chips? I hope to really restore this mac to its original components.

 

[Mac128]

Now as you can see from the pictures, there are two chips missing/removed from the mobo. My question is, can i still start(power on) this mac without the MacMemory RAM board? ... Does anyone knows where can I get those missing chips and original 128k RAM chips? I hope to really restore this mac to its original components.

More than two chips, I count four. And no the board will not power on with those chips missing. It won't hurt anything to try, but it is unlikely.

That's going to be a substantial job to restore the logic board, and it will never be original condition. Your best bet is to start looking for a new one. The really sad part is for those missing chips, they've placed sockets, but not for the new RAM. Very interesting RAM chips by the way - never seen any like them before.

The chips you are missing are easy to replace without any soldering as they will easily socket right in. I am a little concerned about those strange single and double pin sockets at D3, E3 & F3. Do they merely tap into the traces? Or have the traces been severed? The biggest repair you will have is the 7-pin socket at E3. This is where the mini-multiplexer was typically installed to upgrade 128K boards to 512K RAM. It required the board to be physically modified. Look underneath and you will see traces have been physically cut. Possibly at other locations on the board too considering some of the strange sockets. Otherwise, it is typically left empty for a 128K. G4 & F4 are simple resistor arrays like the one at E3. E12 & E13 are identical LS244 chips, which you will see mounted directly above the sockets on the RAM board. I wonder if these were actually removed from the Mac and used on the RAM board?

Note you have the aftermarket resistor array added to D15. This was added to the logicboard in any repair to the 128K to prevent a certain kind of lock-up. It is rare to fins a 128K without this added. And, it was mandatory in a 512K RAM upgrade. This might explain why the board was upgraded and the analogue board still has its upper heat sink fin. On the other hand, it could also be that the logic board is not original and one that had already been prepped for the RAM upgrade and merely swapped for the customers in a quick exchange. Anybody know how common that kind of thing was? The 68000 chip is typical of much later Macs, not one as early as this which would still have the the metal square on top.

There is some good news though. If you intend to merely operate the board as a 128K (not restore it), with the missing chips replaced, severed traces mended, and without any additional circuitry in the D3 location, I understand the additional RAM will not be recognized by the Mac, and the board even with 512K RAM installed, will operate normally as a 128K board. It has always been my intention to find a key connection in a 512K upgrade so install a switch that will simply engage or disengage the circuitry depending on how much RAM I want to use. There's a thread about that somewhere, including one about toggling between 64K & 128K ROMs too. Just never got around to investigating it and didn't want to risk damaging anything without more details.

I have no idea if the 128K SIMMs work with any Mac.

Anonymous Freak – check this out regarding 128K SIMMs.

 

[H3NRY]

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.

 

[Dog Cow]

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

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?

 

[Quadraman]

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.

 

[H3NRY]

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?

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.

 

[Mac128]

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.

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]

Anonymous Freak – check this out regarding 128K SIMMs.

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.