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From: John Levine <johnl@taugh.com>
Newsgroups: comp.arch
Subject: Re: transactions vs interactive, was The Design of Design
Date: Fri, 31 May 2024 00:37:28 -0000 (UTC)
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According to Scott Lurndal <slp53@pacbell.net>:
>>Among the many differences between IBM and DEC computers was that
>>IBM's had channels ...

>Burroughs I/O subsystem offloaded even more than IBM channel
>programs could provide.   It was fire and forget from the MCP
>perspective (e.g. read a set of cards or read a bunch of sectors
>was one instruction that initiated a high level operation (read
>card/cards, print line/lines, read sector/sectors, write sector/sectors,
>backspace tape, etc) and the hardware took care of all the fiddley
>little details.

I can believe that Burroughs I/O was more flexible but IBM 360
channels could ran channel progarms that could be arbitrarily long and
had loops. If you wanted to write a channel program to read a dozen
cards or read all the records on a disk track, that wasn't hard. There
were even some self-modifying channel programs that were a pain to
virtualize on CP/67.

>Modern server-grade I/O hardware is more along the fire-and-forget model than
>bit-twiddling models from the 8086 timeframe.   Even SATA (which
>is more capable than IDE) is fairly high level, as is FC and
>NVMe.  Server-grade NICs are also pretty capable and require
>far fewer interrupts than early NICs to transfer a given amount
>of data.

Yup, now it's all channels all the time.



-- 
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