Path: utzoo!attcan!uunet!tut.cis.ohio-state.edu!ucsd!ames!pasteur!agate!shelby!portia!dhinds
From: dhinds@portia.Stanford.EDU (David Hinds)
Newsgroups: comp.sys.ibm.pc
Subject: Re: SMARTDRV and HighRAM
Message-ID: <10406@portia.Stanford.EDU>
Date: 21 Mar 90 19:23:10 GMT
References: <2606b522-2621comp.ibmpc@ddsw1.MCS.COM>
Sender: David Hinds <dhinds@portia.stanford.edu>
Organization: Stanford University
Lines: 22

In article <2606b522-2621comp.ibmpc@ddsw1.MCS.COM>, andyross@ddsw1.MCS.COM (Andrew Rossmann) writes:
> 
>   Has anyone had any experience in loading DOS 4's SMARTDRV.SYS into the
> High RAM area made available by QEMM? Is it better to run SMARTDRV using
> extended memory, or use expanded memory under QEMM? (I know extended tends
> to be faster, plus I don't do any high-speed serial port reading.)
> 
    I use LOADHI to put SMARTDRV in high memory, and it works fine.  I'm
not sure what the difference between extended and "expanded" memory will
be under QEMM; for a disk cache, both are sufficiently fast that you
won't see much of a net performance difference.  I seem to remember that
the DOS manual recommended using expanded memory for SMARTDRV, but this
may have been aimed at 80286 systems.  A reason that the 386's extended
memory might appear faster than expanded memory is that to access extended
memory, a program calls a BIOS memory move routine.  To access expanded,
a program calls the expanded memory driver, which remaps memory and lets
the calling program do the move.  The BIOS move will be a full 32-bit
block move, while a program using expanded memory will probably use a
16-bit move instruction, for compatibility across processors.

 -David Hinds
  dhinds@popserver.stanford.edu