Path: utzoo!utgpu!watmath!clyde!att!osu-cis!tut.cis.ohio-state.edu!rutgers!rochester!pt.cs.cmu.edu!andrew.cmu.edu!bader+ From: bader+@andrew.cmu.edu (Miles Bader) Newsgroups: comp.arch Subject: Re: Why is the RT slow? Message-ID: Date: 19 Nov 88 16:51:07 GMT References: <5046@polya.Stanford.EDU> , <691@quintus.UUCP> Organization: Carnegie Mellon Lines: 14 In-Reply-To: <691@quintus.UUCP> ok@quintus.uucp (Richard A. O'Keefe) writes: > I doubt whether any of the points Joe Keane listed really explains why > the old RTs were roughly halfway between a Sun-2 and a Sun-3/50 on a > logarithmic scale of speed. There are supposed to be newer versions > that are rather faster. My guess is that it was a marketing decision: > IBM decided to scale the thing to what they thought people would buy > and guessed wrong. Among other things, I have been told that the old rts DISABLED the instruction pipeline when in "virtual memory mode", due to problems with recovering from page faults. Newer models apparently can use the pipeline. -Miles