From owner-freebsd-hackers  Fri Jun 27 05:32:05 1997
Return-Path: <owner-hackers>
Received: (from root@localhost)
          by hub.freebsd.org (8.8.5/8.8.5) id FAA19298
          for hackers-outgoing; Fri, 27 Jun 1997 05:32:05 -0700 (PDT)
Received: from godzilla.zeta.org.au (godzilla.zeta.org.au [203.2.228.19])
          by hub.freebsd.org (8.8.5/8.8.5) with ESMTP id FAA19257
          for <freebsd-hackers@FreeBSD.ORG>; Fri, 27 Jun 1997 05:32:00 -0700 (PDT)
Received: (from bde@localhost) by godzilla.zeta.org.au (8.8.5/8.6.9) id WAA25213; Fri, 27 Jun 1997 22:27:08 +1000
Date: Fri, 27 Jun 1997 22:27:08 +1000
From: Bruce Evans <bde@zeta.org.au>
Message-Id: <199706271227.WAA25213@godzilla.zeta.org.au>
To: abial@korin.warman.org.pl, msmith@atrad.adelaide.edu.au
Subject: Re: Disk built-in hw cache
Cc: freebsd-hackers@FreeBSD.ORG
Sender: owner-hackers@FreeBSD.ORG
X-Loop: FreeBSD.org
Precedence: bulk

>> > I just read certain discussion on Linux list concerning
>> > bad/missing/removed disk cache in "repaired" (and sold as new) hard disks.
>> > Linux prints during probing the size of disk cache (at least that what the
>> > hd will tell it). How to achieve the same result in FreeBSD? There is a
>> > #ifdef WDDEBUG flag in wd.c, around some interesting printfs. Will it give
>> > me this info?
>> 
>> Uhh, this sounds pretty bogus.  Do you have a reference to anything
>> authoratative on the subject?
>
>No :-(. AFAIR from that discussion, IDE disks answer certain query by
>returning the info stored somwhere on cyl 0. How this info relates to

It would probably be stored in the drive's firmware except on ancient
drives.

wdp_buffersize (in wdreg.h) is documented in the old draft of the ATA
spec that I have (revision 4c).  It is the "Buffer size in 512 byte
increments (0000h=not specified)".  `Buffer' doesn't seem to be specified.

>The original story goes like this: those folks bought some disks, saw the
>"0 kB cache" during startup, went to the seller who checked the disk with
>his diagnostic proggy (it also said "0 kB cache"), and then he started

The Linux ide-disk driver just prints wdp_buffersize.  0 means unspecified
:-).  It probably doesn't mean much.

Bruce