Xref: utzoo comp.sys.mac.misc:8041 comp.sys.mac.system:3010 Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!sdd.hp.com!caen!uwm.edu!ux1.cso.uiuc.edu!csrd.uiuc.edu!s4.csrd.uiuc.edu!bruner From: bruner@sp15.csrd.uiuc.edu (John Bruner) Newsgroups: comp.sys.mac.misc,comp.sys.mac.system Subject: Re: mac IIsi slowdown (long) Message-ID: Date: 1 Feb 91 15:16:21 GMT References: <1991Jan31.123728.4540@esat.kuleuven.ac.be> Sender: news@csrd.uiuc.edu (news) Organization: CSRD, University of Illinois Lines: 20 In-Reply-To: wambacq@esat.kuleuven.ac.be's message of 31 Jan 91 12:37:26 GMT In article <1991Jan31.123728.4540@esat.kuleuven.ac.be> Patrick Wambacq describes the bus structure of the IIsi and some experiments he performed to increase the processor speed. I confess that I have not seen any hard technical information about the hardware of the IIsi. Can the video circuitry access bank B? If I understand Patrick's description correctly, it sounds like it can't. Isn't bank A located at the bottom of physical memory (addresses 0..$FFFFF)? If so, doesn't that put the frame buffer right in the middle of the application heap? If the processor runs fastest out of bank B, then it seems to me that in virtual mode (using the MMU) the bank A memory should be dedicated as much as possible to the video buffer, the disc cache, and other memory objects whose access time is less critical to system performance. In that case, running with the MMU would be faster than running without it. Perhaps this will be another feature of System 7? -- John Bruner Center for Supercomputing R&D, University of Illinois bruner@csrd.uiuc.edu (217) 244-4476