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Found a method of upgrading Macintosh 128k memory!

T-Squared

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It's probably already known by now, but I just discovered this yesterday:

https://macgui.com/news/article.php?t=466

I'm already working on it.

But, there is good news. I have preserved the original Apple-branded 128k chips, with one heat-gun treatment. :D (Hey, I'm not that cheap. I'm not going to clip and throw these away.)

I already have cleared one row, and I think I have most of the components that I need. The last one is coming tomorrow. (A multiplexer.)

At least this gives me a reason to use more of the good 256-kilobit memory chips that I got for my Sanyo's memory upgrade project.
 
I think the ultimate thing to do would be to obtain a 512k board to pop in there, that way you could just store the 128k board away without disturbing it. I was thinking about doing that when I was looking at a 128, but ended finding a nice 512 instead, which actually turned out to be a dealer upgraded 128, which I think is awesome.
 
Back in the day, my 128K Mac was upgraded in a dark room of a back office behind a non-descript door in a Pasadena alley. Opportunistic, guerrilla work to be sure.
 
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Congratulations for actually doing the right thing to a 128K Macintosh. ;)

(Although, yeah, you may regret it financially because there do seem to be a lot of bozos out there so obsessed with the idea of having an original, "virginal" 128K Mac, despite the fact that they're utterly useless, that you may have been able to swap your board to one of them for their already period-modified board plus significant cash on top.)
 
an original, "virginal" 128K Mac, despite the fact that they're utterly useless
I'm working on writing an email client, FTP, and Telnet that will work on the Mac 128K. A web browser and Usenet newsreader are also on the to-do list. ;-)
 
I'm working on writing an email client, FTP, and Telnet that will work on the Mac 128K. A web browser and Usenet newsreader are also on the to-do list. ;-)

What are you using for a TCP stack? How are you networking the Mac?

The web browser will be a challenge, everything else should be straightforward. TCP is simply expensive memorywise.
 
Welp, I was wrong. I DON'T have ANY of the passive components I need (except for the logic IC). I'll have to worry about that later.

Anyways, yeah. I got tired of having to worry about "Not Enough Memory!" when I started games like "A Mind Forever Voyaging"...

Also, I had plans, anyways, so I could use up the 256Kbit memory chips that I have.
 
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Ok, I got them. (Plus a replacement click switch for the mouse. The one I have seems very weak. Not enough tactile feeling.) Also, I'm close to completing this. :D One of the older frames I had from before fit perfectly. I mean that as in, the floppy drive was on the proper level, and didn't need anything to level it off. (One of the other frames I had prevented me from pushing in a floppy disk because it was ever-so-misaligned.) Although, it took some work to restore that frame, because it was mostly rusty, and wouldn't look good or be good for the motherboard inside.
 
Congratulations for actually doing the right thing to a 128K Macintosh. ;)

(Although, yeah, you may regret it financially because there do seem to be a lot of bozos out there so obsessed with the idea of having an original, "virginal" 128K Mac, despite the fact that they're utterly useless, that you may have been able to swap your board to one of them for their already period-modified board plus significant cash on top.)

The thing is, I don’t think most collectors are buying a 128 to actually use it, more for historical value. Kinda like the Apple 1, I don’t think those are terribly useful either. A completely untouched base model IBM 5150 REV A from 1981 would be quite useless too, but undeniably cool.

But yes, if you want to use your Mac (like me), you want that 512k.
 
Ok, got everything installed. Now I have a problem. Some memory seems to be bad. I get a short burst of static where the startup bell tone should be, and the image on the screen shows what would be a Sad Mac, except very chopped up and with random, but patterned garbage. I can see numbers (I know its the error code), but even that is very scrambled, and I can't even get a full number (Maybe a few zeroes, an F here and there, etc.)
 
Ok, I did try the 256-kilobit memory I had intended for my Sanyo MBC-775, but that seemed to be borked too. I have more chips on the way.

I'm guessing the system is working correctly if it at least displays an image (or attempts to), right?

The Sad Mac image and numbers are broken up (assuming because of the memory being bad), but the system turns on, and forms an image on the screen.
 
Well, I found one reason. I'm not getting continuity of Pin 6 or Pin 10 of any of the sockets. As in, there is no continuity on ANY pin 6 or pin 10 in the RAM array. I don't know what that signifies. I get continuity on the rest, though.
 
Okay, I bought some memory from Unicorn Electronics, but I keep getting an extremely-corrupted Sad Mac (with some pieces of the picture being repeated horizontally and vertically) and a staticky buzz every time I turn it on, instead of the bell tone it's supposed to produce on startup. The error code is also unreadable, but I'm guessing that this is no ordinary code, because the one letter "F" that I can read doesn't look like it's supposed to be there in relation to the Sad Mac icon. Like "000F0000". The rest is garbage or repeated segments.

My hunch is that a logic chip has failed, because it doesn't work even with multiple brands of chips. I have tested for appropriate continuity, though; memory-to-CPU and memory-to-memory. They seem fine.
 
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Dang it. Even after checking certain attributes to make sure they were working properly, and did some more replacements:

  • Continuity between all respective pins on the memory.
  • Checking to make sure the data lines were connected to the CPU. (And they are, plus the system actually starts up, so I'm assuming that the CPU is executing code)
  • Replaced the 253 Demuxers (just in case there was a problem with the memory select), also replaced more logic chips.
  • Replaced all capacitors on the analog/power board.
The system still starts with a Sad Mac and I have an even worse static-laden screen with a screech in place of the bong chime.

Unfortunately, none of the symptoms match any problems in "The Dead Mac Scrolls". I even adjusted the voltage on the analog board. (It did nothing to fix the problem)

At this point, I'm not sure what is wrong.
 
I would next throw some deoxit or electronics cleaner on the ram slot to rule out bad/tarnished connection.
 
Back in 1986 or so I had my original 128K upgraded with a Levco MonsterMac board. It was a board that added 1.5M, and (IIRC) installed into a socket on the motherboard that replaced the 68000. (You had to either be real good, or sacrifice the original 68K to do that!) For a few years, my main usage of this was to run a "huge" (probably all of the 1.5M!) RAM disk all day, since not much could actually use that much memory. It also attempted to re-use one that was there on reboot, and I never really had corruption problems.

But first, the guy who did it did the "hidden" 512K upgrade. There was a row of holes on the motherboard to install a small board with a multiplexer chip for 256Kbit DRAM, and to swap around the address lines appropriately. I think it was those seven vias at E3.

 
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