Path: utzoo!utgpu!news-server.csri.toronto.edu!bonnie.concordia.ca!uunet!samsung!think.com!linus!progress!billf From: billf@progress.COM (Bill Ferro) Newsgroups: comp.windows.ms Subject: Re: Performance degradation in 386 enhanced mode Message-ID: <1991Jan18.224732.24139@progress.com> Date: 18 Jan 91 22:47:32 GMT References: <4491@mindlink.UUCP> Sender: news@progress.com (The News User) Organization: Progress Software Corp., Bedford, MA Lines: 35 Nntp-Posting-Host: billf a752@mindlink.UUCP (Bruce Dunn) writes: > On some machines, but not all, tasks running in 386 enhanced mode are much >slower than in standard mode. This can be seen by using the computational >index from the Norton Utilities in both standard mode and 386 enhanced mode. >It can also be seen for some programs such as the Microsoft Flight simulator, >which become extremely sluggish in 386 enhanced mode but are ok in standard >mode. > This problem has nothing to do with swap files - disk access is not >involved in demonstrations of the problem. The problem has nothing directly to >do with memory size - the performance difference occurrs between two different >modes on the same machine with the same memory. [other stuff deleted] >Bruce Dunn Vancouver, Canada a752@mindlink.UUCP Bruce, the answer lies in the fact that the enhanced mode uses the virtual 8086 mode of the 386 chip. I am familiar with protected mode on a 386 but not so on the 286. The virtual box created in enhanced mode causes a protection fault on EVERY int instruction and port access. The overhead involved in saving the current task state in the TSS and switching to another task, executing the instruction and returning to the original task is not minimal. Programs like Norton's SI are not a very good indication of overall true speed (or lack thereof) in a virtual mode environment. I do agree though, that 386 enhanced mode is too slow. Another speed problem is that fact that WINDOWS goes through DOS to do file access -- windows is not really an operating system -:( Now, can anyone explain to us why in 286 virtual mode (where only 1 can exist) is faster than 386 virtual mode (many can exist)?????? -- Bill Ferro UUCP: mit-eddie!progress!billf Progress Software Corp. Internet: billf@progress.com 5 Oak Park >>>>>>Opinions expressed herein are Bedford, MA 01730 >>>>>>are usually mine (sometimes