Path: utzoo!attcan!utgpu!jarvis.csri.toronto.edu!mailrus!ncar!ico!ism780c!darryl From: darryl@ism780c.isc.com (Darryl Richman) Newsgroups: comp.unix.i386 Subject: Re: Microsoft Word & (SCO) Unix 3.2 Message-ID: <31897@ism780c.isc.com> Date: 22 Aug 89 13:22:44 GMT References: <7227@megatest.UUCP> <31839@ism780c.isc.com> <1115@ispi.UUCP> Reply-To: darryl@ism780c.UUCP (Darryl Richman) Organization: Interactive Systems Corp., Santa Monica CA Lines: 31 In article <1115@ispi.UUCP> jbayer@ispi.UUCP (Jonathan Bayer) writes: "darryl@ism780c.isc.com (Darryl Richman) writes: ">Only Xenix 286 programs go through the x286emul environment emulator ">program. Xenix 386 programs execute natively. 286 programs vary in ">speed, but are often faster than under either Xenix 286 or Xenix 386 ">because the memory management is significantly faster under x286emul. " "How is the memory management faster in emulation mode than in native 386 mode? The emulator actually gets memory a 64k segment at a time and doles it out as the XENIX program sbrks for it. Requests for memory that the environment emulator already has never go into the kernel and only take a few instructions to map into the 286 program's address space. I don't recall the exact numbers, but frequent requests for small amounts of memory can be an order of magnitude faster. Of course, when the program asks for 64k segments, things are close to equal. They are still faster than under 386 XENIX because the emulator knows that it is running a 286 XENIX program, but XENIX memory management code must check this at each place where handling the memory request must be different between a 286 and a 386. PLEASE NOTE: when I speak of 386 XENIX, I'm talking about version 2.3 or earlier. SCO XENIX V.3.2 is the same code base as UNIX V.3.2. I am not attempting to compare current products. --Darryl Richman -- Copyright (c) 1989 Darryl Richman The views expressed are the author's alone darryl@ism780c.isc.com INTERACTIVE Systems Corp.-A Kodak Company "For every problem, there is a solution that is simple, elegant, and wrong." -- H. L. Mencken