Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP Posting-Version: version B 2.10.1 6/24/83; site watcgl.UUCP Path: utzoo!watmath!watcgl!dmmartindale From: dmmartindale@watcgl.UUCP (Dave Martindale) Newsgroups: net.unix-wizards Subject: Re: movc3 is NOT always faster! Message-ID: <2283@watcgl.UUCP> Date: Mon, 19-Mar-84 17:17:38 EST Article-I.D.: watcgl.2283 Posted: Mon Mar 19 17:17:38 1984 Date-Received: Tue, 20-Mar-84 00:57:15 EST References: <5949@umcp-cs.UUCP> Organization: U of Waterloo, Ontario Lines: 7 Movc[35] normally does 32-bit writes to memory, at least on the 780. Reads are always 64 bits due to the cache. The actual data transfer is slower than doing a movq, since 4 SBI cycles are required for 2 32-bit writes vs. 3 for one 64-bit write. Also, if you have the old MS780C memory controller, a 32-bit write has to do a read-modify-write cycle for any write smaller than 64 bits. The new controllers don't have this problem.