There has been talk about the 68000 chips used in some Lisas and early 128K and 512k macs. These chips come from Motorola (not second sources) and have an SC prefix which was used instead of MC (consumer Motorola) to identify chips for specific customers or custom parts or preavailability parts. You can see one in this prototype mac labeled SC87839L. The Apple part number is 338-0001, I believe. The last line is a date code I believe.
There is information about these chips that was posted to me online
I have two 68000s from that time. While I interviewed with Apple in late 1984, I think I got both chips from the California Institute of Technology EE supply shop in the fall of 1984 for a project I did for my senior year, a VT100 like terminal based on a 68000. Here aree the two chips:
This one is in typical black plastic, and is the G version noted in the table above. I didn't use it (it was a backup) to the chip below I used.
Which is shown in my project on the wirewrap board. It's marked SCN68000, date code 1981. Again an SC chip although it appears this may be a Signetics fab rather than a Mototola fab part. Ceramic 64 pin DIP.
As Apple used these types of chips in early Lisa and Mac devices, perhaps in prototypes, I'm looking for more information. I appreciate any assistance the community may have.
I believe that the Signetics chip is in fact datecode 13th week of 1983. The last line is "C8I64" which is a continuation of the part code: the full part is SCN68000C8I64, indicating a commercial temperature range, 8 MHz bin, ceramic 64 pin package.
You can read the Signetics processor databook from 1986 here. (See page 2-227)
Hey @Anne68k, can we see a large photo of both sides of that Mac 128K prototype?
Would love to see... Thanks in advance.
They aren't my photos but here is the back
MAC Prototype with 68000 experimental chip back.jpg
MAC Prototype with 68000 experimental chip.jpg
That's awesome! Thanks!
Goes to show how much work they put into the project... and it paid off big-time! Thanks for posting.
OK, how many of you own a wire-wrap tool?
Not many.
How many have done a project like this? Few.
I have done some a LOOONG time ago but never like this. Obviously the clock speeds were WAY lower and you could get away with it but I enjoyed being able to prototype with ... just wire.
20250420_131917.jpg
20250420_131949.jpg
If that was a wirewrap prototype of the first 68000 Mac that is pretty cool, and just cool in any event.
I own a wire wrap tool and Vector Slit-N-Wrap wire wrap gun from those days. The hand tool is always reliable as long as your fingers don't start cramping after hours and hours. The gun eliminates this finger fatigue. The gun can be set from 3 to 9 turns, pull the trigger and zzzzzzz, done, next pin. The gun still works.
This is my wirewrap prototype of a 65C02, 32KB SDRAM, interrupt driven co-processor board from around 1984-85 used in my Apple IIe.
ALDC-Prototype-Top.jpg
Here is the bottom side:
ALDC-Prototype-Bottom.jpg
It was the proof of concept for a production run of around 20 of these:
2020 ALDC-1.jpg
Up to four of these co-processor quad DAC boards were used in the IIe along with the AE TimeMaster II H.O. and AE RAMWorks II cards, dual floppy and 80-col. mode for use in laser entertainment . The Apple IIe read TXT time-based command scripts and fed images and display commands to the co-processor boards. There's more to it but this is just about the ease and joy of doing wirewrap prototypes back in the day. I did some other simpler wirewrap prototypes back in 2018-19.
I also did a 6809-based speech synthesizer (phonemes in ROMs) with wire wrap. We also used wire wrap at the NASA JPL with prototypes at that time.
That's an incredible amount of work! I did wire wrapping back in the day but I moved to point to point using wire wrap wire. I found that there were fewer problems with the pins (legs?) getting bent and touching adjacent pins or other components but the build time was about 3X longer. That's a pretty impressive build, no doubt.
Thanks for sharing. I appreciate seeing works of art like this.