Xref: utzoo comp.windows.ms:11895 comp.sys.ibm.pc.misc:8988
Path: utzoo!utgpu!cunews!bnrgate!bwdls58!mlord
From: mlord@bwdls58.bnr.ca (Mark Lord)
Newsgroups: comp.windows.ms,comp.sys.ibm.pc.misc
Subject: Re: OS/2 2.0 is here!  READ THIS, you'll be impressed
Message-ID: <6567@bwdls58.bnr.ca>
Date: 24 Apr 91 17:57:43 GMT
References: <1991Apr21.135534.724@jarvis.csri.toronto.edu> <1991Apr21.194928.8267@ux1.cso.uiuc.edu> <1991Apr21.175529.2386@jarvis.csri.toronto.edu>
Sender: mlord@bwdls58.bnr.ca
Reply-To: mlord@bwdls58.bnr.ca (Mark Lord)
Organization: Bell-Northern Research, Ottawa, Canada
Lines: 33

<1) Disk *writes* can be buffered under HPFS.  As far as I know, all
<   the DOS disk cachers under FAT are write-through, so that you can
<   turn your machine off immediately after doing a write without losing

Most DOS disk cachers I have used include staged/delayed writes to disk,
including re-ordering for optimal access in some, and elimination of redundant
writes in others.  But perhaps HPFS has other benefits besides this.

<OS/2 applications under Presentation Manager.  I'm not sure about graphics
<programs; I've read so much info internally over the past 2 days.  I
<*do* recall someone talking about a bug being fixed that allowed some
<graphics programs to be *displayed* under PM.  In fact Windows 3.0 in
<enhanced mode can display DOS graphics programs in a window -- it can't
<*run* them all because most do direct writes to the video RAM and thus
<can't run concurrently with Windows.  I suspect PM (Presentation Manager, 
<the window manager for OS/2) has similar limitations.  You probably wouldn't
<want to do this anyway.  Trapping I/O instructions for writing out blocks
<of data to disk and translating to OS/2 calls can be done fairly efficiently.
<But trapping individual machine language instructions that access video
<memory would be incredibly slow no matter how smart you did it.  Windows 3.0

The "smart" method, used by DesqView-386 and perhaps others, is to simply use
the 386 virtual memory to remap "normal" memory in place of the task's 
apparent "video memory", and let it write away at will.  The supervisory code
periodically refreshes the window on the "real" screen from the virtual windows
of each such nasty program.
-- 
MLORD@BNR.CA  Ottawa, Ontario *** Personal views only ***
begin 644 NOTSHARE.COM ; Free MS-DOS utility - use instead of SHARE.EXE
MZQ.0@/P/=`J`_!9T!2[_+H``L/_/+HX&+`"T2<TAO@,!OX0`N1(`C,B.P/.DS
<^K@A-<TAB1Z``(P&@@"ZA`"X(27-(?NZE@#-)P#-5
``
end