Junkbox CP/M system? - test-drb@ccmp.vtda.org

24 Apr 2007

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Subject: Re: Junkbox CP/M system?
   From: Holger Veit <holger.veit at iais.fraunhofer.de>
   Date: Tue, 24 Apr 2007 15:35:10 +0200
     To: General Discussion: On-Topic Posts Only <cctech at classiccmp.org>

Allison schrieb:
   On CF,
IOCS16- is honored--but it's not on any IDE  hard drive you're 
 going to buy today.

 I've heard that was true of any drive over 500mb and have not seen anything
 over 80mb that does. 

 Me I keep saying if you really need the simplicity of 8b transfers and 
 the low cost that comes from a surplus IDE drive just ignore the high 8bits
 and enjoy it.  There's no harm from that.  So what if half the storage
 is unused, likely the drive is large anyway.
    You are going to lose the error flags from the status register which a 
transferred on D8-15, IIRC.
Also the drive identify command will return only half of the data.
It is not an issue with pure data blocks; you'll then just have 256 byte 
blocks rather than 512. 
Both are minor issues.  CP/M cannot use the identify and a bios that uses it
to configure is going to grow far to fast.  The error bits are a minor problem,
sufficient to say if you get an error (low 8bits signal generic error) whats
one to do? Answer, not much as something big happened.  CP/M doesn't handle 
errors the bios does.  It's simplistic but 99.999% of the time unless there's
a programming error where the host and drive are out if sync, errors mean
it's time for a new drive.

Allison

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-- 
Holger