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From: John Levine <johnl@taugh.com>
Newsgroups: comp.arch
Subject: Re: Architectural implications of locate mode I/O
Date: Thu, 1 Aug 2024 21:01:12 -0000 (UTC)
Organization: Taughannock Networks
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According to Stephen Fuld  <sfuld@alumni.cmu.edu.invalid>:
>On 7/31/2024 6:41 PM, Lawrence D'Oliveiro wrote:
>> On Sat, 6 Jul 2024 06:15:56 -0000 (UTC), Stephen Fuld wrote:
>> 
>>> As you posted below, the whole PDS search stuff could easily be a
>>> disaster.  Even with moremodest sized PDSs, it was inefficient has
>>> hell.
>> 
>> Would locate mode have helped with this?
>
>No.  The problem was that the PDS search was a linear search of records 
>on the disk drive i.e. typically multiple disk revolutions), and 
>furthermore, it required (until the fast PDS search came along) that the 
>host channel take action on each disk record checked, even the ones that 
>didn't match, including resending the search argument to the disk 
>controller.
>
>This has nothing to do with locate mode.

He's made it painfully clear that he doesn't understand the relative
speed of CPUs and disks, or the costs of multiple I/O buffers on
systems with small memories, particularly back in the 1960s when this
stuff was being designed. Nor how records in COBOL data divisions were
designed so implementations could read and write file records directly
from and to the buffers, and the IOCS of the era enabled that in COBOL
and other languages.

Perhaps this would be a good time to stop taking the bait.  I thought
this silly argument was over a month ago.

-- 
Regards,
John Levine, johnl@taugh.com, Primary Perpetrator of "The Internet for Dummies",
Please consider the environment before reading this e-mail. https://jl.ly