Path: utzoo!utgpu!news-server.csri.toronto.edu!rpi!zaphod.mps.ohio-state.edu!mips!mash From: mash@mips.com (John Mashey) Newsgroups: comp.arch Subject: Re: Segmented Architectures ( formerly Re: 48-bit computers) Message-ID: <1655@spim.mips.COM> Date: 30 Mar 91 23:08:43 GMT References: <1991Mar27.172325.10800@sj.nec.com> <00670208556@elgamy.RAIDERNET.COM> Sender: news@mips.COM Organization: MIPS Computer Systems, Inc. Lines: 23 Nntp-Posting-Host: winchester.mips.com In article <00670208556@elgamy.RAIDERNET.COM> elg@elgamy.RAIDERNET.COM (Eric Lee Green) writes: >2) Maintaining large objects that grow and shrink. In a sequential address >space, often you can't "grow" an object because something else has been >allocated in the addresses immediately afterwards. And thus you may end up Actually, I Don't think this quite right. Consider the difference between a scheme that has X-bit segment numbers and Y-bit byte addresses within the segment, and compare with one that has an X+Y-bit flat address space. In the first case, using typical designs, you get 2**X segments of size 2**Y, which usually means that objects are CONVENIENTLY 2**Y maximum size. the X+Y-bit flat address machine can simulate the same thing rather conveniently... On the other hand, the X+Y-bit flat machine can provide 2**(X-1) segments of size 2**(Y+1), 2**(X+1) segments of size 2**(Y-1), etc. In both cases, if things get larger than the space reserved, you have to work harder, but in general, the flat-addressing machine may have the convenience of variable granularity. The segmented design may, or may not. -- -john mashey DISCLAIMER: UUCP: mash@mips.com OR {ames,decwrl,prls,pyramid}!mips!mash DDD: 408-524-7015, 524-8253 or (main number) 408-720-1700 USPS: MIPS Computer Systems MS 1/05, 930 E. Arques, Sunnyvale, CA 94086