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From: jalbert@IRO.UMontreal.CA (Francois Jalbert)
Newsgroups: comp.sys.ibm.pc.misc
Subject: Is DOS 5.0 really so slooow!
Summary: DOS=HIGH slows you down?
Keywords: Landmark
Message-ID: <1991Jun20.223605.18977@IRO.UMontreal.CA>
Date: 20 Jun 91 22:36:05 GMT
Sender: news@IRO.UMontreal.CA
Reply-To: jalbert@IRO.UMontreal.CA (Francois Jalbert)
Organization: Universite de Montreal
Lines: 40


I successfully avoided upgrading from 3.3 to 4.0, but now I am faced with 5.0.
When a friend of mine got 5.0, I was quite happy at the prospect of hearing 
about his experience with the new DOS.

I learned about a new help facility. I already have one such stand-alone help 
program. I learned about some new utilities, I also have more such stand-alone 
utilities than I really care for. The same hold for intelligent command 
reentry. In fact, the more I thought about it, the more the only way to 
justify DOS 5.0 was because it leaves more conventional memory for the 
application programs.

It's not that I am desperate for memory. 90% of my programs don't use anything 
near 640K. The last few remaining ones use my 3Mb RAM-disk for temporary 
files, so the slow-down is minimized. So I don't really need more than my 
usual 550K of free memory. Nevertheless, I thought that having (say) 600K free 
might be nice. Especially since DOS 5.0 seems reasonably priced. 

The Landmark (version 2.00) index for an ordinary 12 MHz 286 is 15.8; about 
6.4 times the speed of an XT. But my friend found that as soon as he uses 
DOS=HIGH (I guess that's in the CONFIG.SYS, I'm not sure) to get more free 
conventional memory, the Landmark index falls down to a miserable 11.3, about 
6 times the speed of an XT. 

I can understand a slow-down when accessing DOS buffers and doing some PATH 
search on a 286 with its lousy mode switching instruction. (although I heard 
some undocumented instruction is available to do it quickly) But I can't 
understand the slow-down would be permanent. Is DOS 5.0 using the tick 
interrupt to fiddle in the extended memory regularly. Strange!

Perhaps the Landmark test is the one to blame. Perhaps it measures DOS' 
performance by asking DOS to do just such operations as internal buffer 
flushing, PATH scanning, etc. Operations requiring the mode switch.

Anyway, I thought I'd ask anybody out there to try to find out if you do also 
experience on your 286 this awful slow-down. Now, that is reason enough for me 
never to touch DOS 5.0, but I can't think Microsoft would make such a mess of 
such a nice idea. It has to be the Landmark test. 

Anybody cares to reassure me? I am somewhat perplexed. Thanks! Franky