Aucbvax.2945
fa.unix-wizards
utzoo!decvax!ucbvax!unix-wizards
Fri Sep 4 14:24:59 1981
[Jcp: Re: [decvax!pur-ee!p: UNIBUS problems on new processors]]
>From mike.bmd70@BRL Fri Sep 4 14:14:05 1981
----- Forwarded message # 1:
Date: 4 Sep 81 14:44:42-EDT (Fri)
From: Jcp at bmd70
To: Michael Muuss <MIKE@BMD70>
Subject: Re: [decvax!pur-ee!p: UNIBUS problems on new processors]
Mike:
From the drawings I have seen, (and the 11/24 I have seen), the
UNIBUS on both 11/24's and 11/44's goes thru a PAX (Program Address
Extension) Module if you are using more than 128Kw of memory. This
produces similar problems as the UNIBUS MAP on an 11/70, and the other
extended memory processors. In additon, on the 11/24, memory managment
is done by a VLSI chip, which incurs additional delay.
On an 11/70, the KT (mem. manager) introduces ~90nsec of delay
and the UNIBUS MAP is good for another 90.
My impression is that on the 11/24, the KT is good for ~100nsec
and the UNIBUS MAP for another ~100nsec, making the 11/24 UNIBUS
good for a little less than 1Mhz. (11/70 is 1Mhz).
Incidentally, the same is true for an 11/23 (Qbus), except that
there is no PAX for the 11/23, yet. (Yes, DEC is planning to
introduce one...)
You may want to relay this info.
-JCP-
----- End of forwarded messages
-----------------------------------------------------------------
gopher://quux.org/ conversion by John Goerzen <
[email protected]>
of
http://communication.ucsd.edu/A-News/
This Usenet Oldnews Archive
article may be copied and distributed freely, provided:
1. There is no money collected for the text(s) of the articles.
2. The following notice remains appended to each copy:
The Usenet Oldnews Archive: Compilation Copyright (C) 1981, 1996
Bruce Jones, Henry Spencer, David Wiseman.
