Path: utzoo!utgpu!news-server.csri.toronto.edu!rpi!zaphod.mps.ohio-state.edu!caen!spool.mu.edu!uunet!mcsun!unido!unidui!veit From: veit@du9ds3.uni-duisburg.de (Holger Veit) Newsgroups: comp.sys.ibm.pc.misc Subject: Re: Is DOS 5.0 really so slooow! Message-ID: Date: 24 Jun 91 15:11:59 GMT Article-I.D.: du9ds3.veit.677776319 References: <1991Jun20.223605.18977@IRO.UMontreal.CA> <1991Jun23.034521.7819@galileo.cc.rochester.edu> <8043@spdcc.SPDCC.COM> <91174.112235DSB100@psuvm.psu.edu> Sender: @unidui.uni-duisburg.de Organization: Rechenzentrum Uni-Duisburg Lines: 58 In liberato@dri.com (Jimmy Liberato) writes: >DSB100@psuvm.psu.edu (David Barr) writes: >>In article <8043@spdcc.SPDCC.COM>, jin@spdcc.COM (Jerry Natowitz) says: >>>In article <1991Jun23.034521.7819@galileo.cc.rochester.edu> >>>gwni@troi.cc.rochester.edu (G. Wayne Nichols) writes: >>>>My experience indicates that any use of HIMEM.SYS will dramatically >>>>slow down the Landmark rating, if not your actual system. >>>I have played around with various configurations and found that EMM386 seems >>>to be the culprit - my apps are runjning in protected mode when I use it for >>>upper memeory access. I don't even have to do any devicehighs or loadhighs, >>>just having emm386 noems is enough. Maybe I'll try removing himem for laughs. >>Yes, if you think about it, it is obvious. EMS memory is _paged_ memory. >>That means when an application requests memory that is not in the 64K page >>frame, the page is swapped out, and another is brought in. This is a >>ludicrous system for managing memory, but for some stupid DOS programs, >>this is required, even on a 386. XMS is faster than EMS because it is >>a direct access system. If an application needs a memory value in XMS, >>it merely addresses it and reads it. I never use EMS unless I want to >>slow my system down. =) >OK, but the original poster was talking about his 286 system, so EMM386 >is not a problem. Further, why would paging a problem on a 386? The previous >poster mentioned that he noticed a problem even with the EMS services turned off >(EMM386 NOEMS). >So, is it HIMEM.SYS that is the culprit? Is the MSDOS 5.0 EMM386 also an XMS >driver ala QEMM or is HIMEM.SYS necessary. It would seem that HIMEM.SYS would >be the only item common on both a 286 and a 386. >-- >Jimmy Liberato liberato@dri.com > ...uunet!drivax!liberato > "Truly great madness can not be achieved > without significant intelligence." -Henrik Tikkanen On a 286, the performance pig is probably himem.sys. The 286 has no direct operation to switch back from protected mode, which is necessary when accessing extended memory. It achieves it by two things: the undocumented operation LOADALL (to copy data between real and extended memory) and a "triple-bus-fault" to fall back int real mode from protected mode. Both operations are very expensive in time. If MSDOS 5.0 or FILE buffers are loaded behind the 1MB+64K barrier, the necessary (pseudo) paging operations may really slow down the system. (My opinion on this, could't checked this on my system, have a 386 only :-) Holger -- | | / Holger Veit | INTERNET: veit@du9ds3.uni-duisburg.de |__| / University of Duisburg | BITNET: veit%du9ds3.uni-duisburg.de@UNIDO | | / Fac. of Electr. Eng. | UUCP: ...!uunet!unido!unidui!hl351ge | |/ Dept. f. Dataprocessing |