I was well aware of the comment in V6, but had no idea what it referred to. When Dennis and I were porting what became V7 to the Interdata 8/32, we spent about 10 frustrating days dealing with savu and retu. Dennis did his most productive work between 10pm and 4am, while I kept more normal hours. We would pore over the crash dumps (in hex, then a new thing for us--PDP-ll was all octal, all the time). I'd tinker with the compiler, he'd tinker with the code and we would get it to limp, flap its wings, and then crash. The problem was that the Interdata had many more registers than the PDP-11, so the compiler only saved the register variables across a call, where the PDP-11 saved all the registers. This was just fine inside a process, but between processes it was deadly. After we had tried everything we could think of, Dennis concluded that the fundamental architecture was broken. In a couple of days, he came up with the scheme that ended up in V7.

It was only several years later when I saw a T-shirt with savu and retu on it along with the famous comment that I realized what it had referred to, and enjoyed the irony that we hadn't understood it either...

Steve

----- Original Message -----
From:
"Brantley Coile" <brantleycoile@me.com>

To:
"Larry McVoy" <lm@mcvoy.com>
Cc:
<tuhs@tuhs.org>
Sent:
Mon, 16 Jan 2017 05:11:02 -0500
Subject:
Re: [TUHS] Article on 'not meant to understand this'