Posts: Cables

Serial console cable for an old Mac

I'm currently working on the NetBSD/mac68k kernel to migrate it from the old rcons framebuffer driver to a more modern one that supports colors, virtual terminals, custom fonts and all other assorted goodies that come with wscons. Unfortunately, I've found a very mysterious system hang-up with my code that I cannot easily debug from the machine itself because the console does not work at all. Hence, I needed to have a serial console for this machine, a Performa 630.

The problem is that old Macintoshes use a DIN-8 connector for their serial line, as opposed to the DE-9 (or DE-25) used in PCs. Fortunately it is possible to connect the two by properly wiring a conversion cable, and that's what I've done today. My first attempt failed because I built a DTE-DCE cable (used to connect to modems and other communications equipment), but in the end I got it, which resulted in a "null-modem" cable to connect the two machines.

Here is the scheme I used:

DIN-8 (DTE)	DC-9 (DCE)	DC-9 (DTE)
1	7	8
2	8	7
3	3	2
4	5	5
5	2	3
6	N/C	N/C
7	N/C	N/C
8	5	5

N/C stands for "Not connected". Use at your own risk.

September 5, 2007 · Tags: cables, mac
Continue reading (about 1 minute)