FYI: The sources to CDL are in the TUHS archives.   

On Fri, Feb 10, 2023 at 7:56 AM Douglas McIlroy <> wrote:
CDL was for designing wired circuit boards, not integrated circuits..
It was used to design the Datakit switch, the Belle chess machine and
other hardware.

I suspect the cited IC-design tool was one that Steve Johnson created
for use in a short course that Carver Mead taught at Bell Labs. I am
not aware that it saw use outside of that course.


On Fri, Feb 10, 2023 at 12:37 AM Christian Dreier via TUHS
<> wrote:
> Hello there,
> I recently watched an old Unix promotion video by AT&T on YouTube (AT&T
> Archives: The UNIX Operating System: and
> they mention a design tool for integrated circuits (apparently named
> L-Gen or lgen; timestamped link:
> Part of this software is a language implemented with YACC that appears
> to describe the behavior of digital logic, like modern hardware
> description languages, i.e. Verilog and VHDL.
> Does anyone have information about this, in particular:
> - Documentation
> - Which projects were realized with this?
> - Source code, if possible
> I asked this question on (see
> but so far there
> is no satisfying answer. A "Circuit Design Language" (CDL) is mentioned
> and there is some good information about it but it has another syntax
> (as shown in the video vs. the documentation about CDL) and apparently
> another purpose (description of board wiring vs. logic behavior).
> Best regards,
> Christian
Sent from a handheld expect more typos than usual