Subject: Re: Again: Booting a Vax-Server 3100 with NetBSD-1.4
To: None <email@example.com>
From: Andrew Phillips <firstname.lastname@example.org>
Date: 06/23/1999 16:45:03
>However, for whatever reason, the most significant word of a longword
>was stored first in memory; I don't remember if that was a software
>convention, or a hardware thing.
Funnily enough, I happen to have the RSX-11M 4.1 vol 5
i/o drivers development and ref manual on my desk. (Nov 1981)
A rather superficial skim of this yields,
Appendix A (development of the address double word) says;
"The addressing in a mapped system uses virtual addresses
and memory mapping hardware. I/O transfers, however, use
physical addresses 18 bits in length. Since a PDP word size
is 16 bits, some scheme is needed to represent an address
Section 184.108.40.206 (4-32) says
For NPR device drivers the layout is as follows.
bit 0 Go bit
bits 1-2 function code
bits 4-5 Memory extension bits
bits 6 interrupt enable
bits 7-15 MBZ
bits 0-15 The lower 16 bits of the address.
So, i/o hardware. Probably what happened is that they stuffed
the extra 2 address bits into the "setup word" that preceded it,
as a wild guess.
Don't know if that has anything to do with the price of tea in
china, but hope it helps :-).
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