From mboxrd@z Thu Jan  1 00:00:00 1970
From: will.senn@gmail.com (Will Senn)
Date: Wed, 9 Dec 2015 12:06:04 -0600
Subject: [TUHS] v6tar from v7 on v6, too large?
In-Reply-To: <20151209175024.5180118C0C7@mercury.lcs.mit.edu>
References: <20151209175024.5180118C0C7@mercury.lcs.mit.edu>
Message-ID: <56686D8C.30705@gmail.com>

Noel,

Comments below:

On 12/9/15 11:50 AM, Noel Chiappa wrote:
>      > From: Will Senn
>
>      > my now handy-dandy PDP11/40 processor handbook
>
> That's good for the instruction set, but for the memory management hardware,
> etc you'll really want one of the {/44, /45, /70, /73, etc} group, since only
> those models support split I+D.
I have the pdf for the /70, but I just ordered a new paper copy on 
Amazon, call me old fashioned :).
>
>      > the 18 bits holding the word 000407
>
> You mean '16 bits', right? :-)
Yes you are correct, 5 octal digits, only 16 bits used for instructions.

>      > This means that branches are to 9th, 10th, 11th and 7th words,
>      > respectively. It'll be a while before I really understand what the
>      > ramifications are.
>
> Only the '407' is functional. (IIRC, in early UNIX versions, the OS didn't
> strip the header on loading a new program into memory, so the 407 was actually
> executed.)  The others are just magic numbers, inspired by the '407' - the
> code always starts at byte 020 in the file.
OK. This is up as my next investigation and it will be guided by 
Lions'... figuring out exactly how programs get loaded in v6 and 
secondarily v7.

Thanks,

Will