To: opendos AT delorie DOT com X-Comment-To: "Patrick Moran" References: <004c01c05a76$4732db90$c5881004 AT dbcooper> Message-Id: <2.07b7.12T7Y.G4UHO7@belous.munic.msk.su> From: "Arkady V.Belousov" Date: Thu, 30 Nov 2000 18:57:43 +0300 (MSK) Organization: Locus X-Mailer: dMail [Demos Mail for DOS v2.07b7] Subject: Re: BASIC & EMS (was: Optimizing CONFIG.SYS...) Lines: 54 MIME-Version: 1.0 Content-Type: text/plain; charset=koi8-r Content-Transfer-Encoding: 8bit Reply-To: opendos AT delorie DOT com X-Comment-To: Patrick Moran Hi! 29-ξΟΡ-2000 19:19 pmoran22 AT yahoo DOT com (Patrick Moran) wrote to : >> W.R.T. EMS, I recall reading somewhere that, rather than being >> "Extremely inefficient", EMS is actually more efficient than XMS >> (when based on either real hardware or the 386's magic tricks). >> There were also "EMS simulator" software (286 stuff?), which >> had to copy data to/from the page frame, hence these were >> indeed inefficient - perhaps you were thinking of these? PM> That could be or maybe I am thinking of the way MS crap for DOS 5 did it. PM> You first had to have Extended memory then that is converted to EMS memory. Not necessary. For example, QEMM (unlike EMM386) gives access to all extended memory through both EMS and XMS API simultaneously. PM> However, no matter how it is done, you have a tiny little 64K window of PM> memory to shove stuff through from expanded memory to conventional memory PM> and conventional memory to expanded memory. When you use something like Not necessary. You can work with data directly in EMS pages (four 16K pages in 64K EMS frame). PM> Desqview and you have a large program over 500k in size and have to swap PM> portions of it out 64k at a time in 16k chunks. Even in this case using EMS can be faster than XMS: for EMS you use plain "MOV CX,8000h/REP MOVSW" eight times+eight times EMS pages remapping, with XMS you use block copying with (possible) much higher overhead for copy. PM> XMS. When a program is run in protected mode, there is no swapping, it PM> operates in exntended memory as originally designed to do. In virtual 86 Hm. Don't mix XMS and protected mode operation. PM> mode you can actually have a full 8086 computers installed many times and PM> each can share entended memory. This is what the DRDOS Task manger does. It PM> does not use EMS like Desqview and other so-called multitaskers do via EMS PM> memory. Again: don't mix memory manager itself and XMS/EMS specifications. PM> I am not positive what XMS memory is, it is not talked about in "DOS Beyond PM> 640K" book. I do remember something about QEMM converting Extended memory to PM> EMS then converting EMS memory back for use as Extended memory, which is PM> really, really stupid. Why not just use Extended memory directly like DPMS PM> does????? ? You something muddle. QEMM doesn't "convert" anything. They simply gives access to extended memory through EMS and/or through XMS API.