EEVblog #414 - Apple Macintosh SE Teardown

What's inside a vintage 1988 Apple Macintosh SE?

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[robertmahn]

I haven't heard those sounds in over 20 years. Sent a shiver down my spine.

[googletheMcLarens]

Oh the memories!
There was a plastic thingy that clipped onto to the case and stuck through to push the two "programmers" buttons on the board. I remember them being a hard reset and an interrupt button. Very handy while programming. At least if you programmed like I did.
I had one of these in college. I added a board that upgraded it to 16MB(?) and attached a "two page" black and white monitor. I wrote my thesis in MacWrite on it.
Thanks for a good tear down and some memories.

[Gracana]

Oh also, I don't know if anyone has mentioned, but those two tactile switches on the motherboard are a reset switch and a non maskable interrupt switch, aka the "programmer's button." Pressing it brings up a little debugger window, which could be replaced by a program called "macsbug" to give you some powerful debugging tools. If you needed to use those buttons often, you could get a small plastic widget that fit onto the side of the case and reached through the vents to actuate those buttons.

[PuchMaxi]

Hi Dave, the buttons you found is actually a programmer's key, or interrupt button an a reset button! For debugging purposes only, they are reachable from the outside using the programmer's switch.

[leehmz]

Yeah, the "20SC" in these old SEs is a MiniScribe 8425SA, made especially for Apple. The 8425 it's based on is an MFM drive, and so it's good for *maybe* 400 kB/s if you're lucky. One of the neat things about this is that it had timer auto-park...if you let it idle long enough, it'd park the heads by itself.

Someone further down had mentioned Rodime, and no, they didn't use those here, but Apple did use a Rodime with an odd proprietary interface in the old HD20 external drive (which attached to the floppy port and was very slow, as I understand it).

[brokenscart]

It amazes me that these still work, booting just like the did over two decades ago.

[drtbantha]

The reset and interrupt switches were on the side -- you snapped a plastic assembly onto the cooling slots on the side which enabled pressing the buttons through the case.

The interrupt button launched the built-in disassembler by default ( gave a ">" prompt in a dialog window) but you could install other alternative debug tools as well.

[MurrayPearson]

A few details from an old-skool Mac-head (now reformed; I use Ubuntu).

The keyboard reset switch had no function on the SE series but was used as a power switch on the Mac II series which had software-controlled latching power supplies. It took advantage of a spare pin in the ADB cables. Interesting note: you could use an S-video cable as a really long ADB cable if you needed.

The expansion slot was called NuBus. Adding the card did not require the user to get near the CRT as it fed through the horizontal slot in back. I never saw an SE series machine with a card, but NuBus cards were common in Mac II series machines. I used a Mac IIfx for a few years: its ADB controller chips were in fact two 6502 CPUs! I decided that IIfx meant "II f-ing expensive." It cost $20, 000 new with 4MB RAM and an 80MB SCSI hard disk, and a 50MHz 68030 CPU!

The two mystery buttons on the side of the mobo are the "programmer's switch". The front one (if memory serves) was a reset button and the other one issued an interrupt so developers could call up a debugger.

[video]

The two tactile switches are the reset and debug buttons. There's a special "programmer's switch" which is a piece of plastic that protrudes through the vents in the side of the case that allows programmers to use them. Theyre used to break into the debugger and reset the 68K.

[TheEphemeris]

Those circuit lines on the PCB are just beautiful. All parallel in mostly one direction, just so cool! Correct me if I'm wrong, but I don't feel like modern boards have quite that beautiful style.

[SuperHouseTV]

I still have a specially modified Torx driver in my tool drawer just for vintage Macs: about 20 years ago I cut a regular Torx driver in half and welded a little extension in the middle to make it easy to reach those screws inside the handle.

[ForViewingOnly]

THANKS DAVE. Being a vintage computer enthusiast I always enjoy a good teardown like this. In fact, I first found EEVblog 3 years ago when I stumbled on your Tandy 1000 teardown. All the best..

[ziginox]

Dave, I'm sure you've figured it out but that isn't the original keyboard. Also, the two tactile switches on the board are for reset and interrupt. There's normally a button panel that snaps onto the side of the machine with fingers that reach through the slots in the case to push them.

[mima]

The hard drive is a Miniscribe model 8425 (which also existed with the ST506/MFM interface), with stepper motor head actuator. It was a very common drive back in the days and quite a big number of these arrived at today still working or at least in a restorable state.
I suggest to desolder the old battery as a lot of them were prone to literally explode and spill acid all over the mainboard and even on the chassis! I saw some months ago a Mac SE/30 with what were the remainings of a Maxell battery, which exploded and its acids corroded badly the mainboard and even the metallic chassis over it until the point it became rusty! Do it as soon as you can to prevent this disaster, I personally put away all the batteries in my old Macs.

[bertblankenstein]

Worked on the Mac SE/30 back in the early 90s. The trick to taking the case off is to place your hands on the sides and yank it back. Next step was to remove the CRT yoke plate to protect the CRT. A common problem was that the hard drive would get stuck in the park position. This was easily cured by giving the right side of the unit a good slap with the hand, at the height of the floppy drive, and the system would boot up.

[ferchrissakes]

Dave, see if you can get your hands on a NeXT computer (no idea how easy that'll be Down Under - or anywhere, really). NeXT were really proud of their hardware and manufacturing (here's their detailed presentation of the motherboard production: watch?v=sT6aphdX0rI ). It's basically the exact same processes as today - just 25 years ago!
For the uninformed: NeXT was Steve Jobs's 2nd computer company after he got fired from Apple in 1985. They built advanced high-end UNIX-based workstations, and their OS is the basis for current day Mac OS X. An expensive niche computer to be sure, but lots of advanced stuff in there with tons of impact on current tech (not just Macs). Noteworthy: Tim Berners-Lee used a NeXT machine to create the World Wide Web. So yeah, big tip of the hat to NeXT!

[Reparaturkanal]

One thing I believe should have been mentioned, that the difference in the modem-port and the printer-port were only in the nomenclature. When you added any device to one of those two ports, you had to tell the computer into which port you plugged them in to. Usually you saw the same symbols on the software side as you saw on the back of the computer. I've been asked one too many times, why you couldn't connect a modem to the printer-port, yet YOU CAN ! Also, you could connect a printer to the modem-port, they are both exactly the same !

[BlackEpyon]

I've got a couple vintage computers that I still play on. One of them, a Tandy 1000HX is as old as I am (1987), and still works, with the exception of the RTC chip. Phillips used to make 24 pin packages that would plug in under the BIOS, with the BIOS piggybacking into that, since RTC clocks weren't really a standard feature on PCs at the time, and that's what this machine has. The battery on that chip JUST RECENTLY crapped out after 30 years, and they're rated to last for 10! That's a NASA warranty for you there! Had to dremel into the chip to cut the connections to the two button-cell batteries, and bodge some wires to connect another battery. It works again :D

I'm no Apple fanboi either, but I still find the vintage Macs fascinating.

[techtron]

24:45 for the startup! Awesome sounds of that Miniscribe! Gotta miss those stepper motor sounds!

[ChurchOfTheHolyMho]

This brings back memories... Thanks so much...
And reading the other comments about debugging - I'd forgotten about the "Even Better Mr Bus Error" extention... :) Those were the days..