Path: utzoo!censor!geac!torsqnt!hybrid!scifi!bywater!uunet!microsoft!philba
From: philba@microsoft.UUCP (Phil BARRETT)
Newsgroups: comp.windows.ms
Subject: Re: Drive>1024 tracks
Message-ID: <71635@microsoft.UUCP>
Date: 2 Apr 91 16:38:33 GMT
References: <1991Mar25.104137.20709@agate.berkeley.edu> <2010008@hplvec.LVLD.HP.COM>
Reply-To: philba@microsoft.UUCP (Phil Barrett)
Organization: Microsoft Corp., Redmond WA
Lines: 47

In article <2010008@hplvec.LVLD.HP.COM> calloway@hplvec.LVLD.HP.COM (Frank Calloway) writes:
>
>It isn't a question of whether SMARTDRV.SYS will work with your hard disk.
>The bottom line is that *MS-DOS* does not directly support drives that have
>more than 1024 cylinders.  Thus, it doesn't matter what SMARTDRV can or
>cannot do.

Sorry but this is incorrect. The limitation is in ROM BIOS INT13 interface.
The cylinder is specified with 10 bits of info.  If the limitation were in 
MS-DOS, no driver alone would solve the problem.  Check any rom bios tech
ref.

>
>A warning: From what I've read, all of the disk manager programs have
>conflicts with SMARTDRV.  When Microsoft wrote SMARTDRV, they broke their
>own rule and let it write directly to hardware (instead of going through
>the BIOS calls).  Unless Microsoft has fixed this incompatibility, using
>SMARTDRV and disk manager software together can corrupt data on your
>hard disk. (Trust me -- I've personally seen it happen :)).

I dont know where you heard this but Smartdrv *does not* write to the
hardware, it calls (er, ints) the ROM BIOS INT13.  What ever rules you
are refering to, they weren't broken.  The conflict is much more subtile
than just `all disk managers'.  There are two cases where you should not
use smartdrv and a disk manager:
	- drive type does not match the selected ROM BIOS supported drive
	  type. For example, you get a new disk and cant find a cylinder/surface
	  match in the list of drives that your ROM BIOS supports -- dont
	  use smartdrv.
	- your drive has > 1024 cylinders (and you want to use beyond 1024)

Also, one special case where smartdrv is OK for >1024 cylinder drives is
if you have a `cylinder mapping' controller that makes the drive look like
a ROM BIOS supported drive.  

By the way, you should read the PC-Week study on windows and disk caches.
Its got some interesting info and points out a cache that does write
to the HW (and its not smartdrv).  It was either in a late feb or early march
issue.


Cheers!
Phil Barrett
Microsoft

standard disclaimer applies -- the above does not necessarily reflect
the views of my employer,