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 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 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.