Re: transactions vs interactive, was The Design of Design

On Fri, 31 May 2024 00:37:28 -0000 (UTC)
John Levine <johnl@taugh.com> wrote:

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.
 
 
 

I don't think so.
The processor and the rest of the hardware on server-grade NIC are more
like IBM PP than like IBM CP.
There were attempts to use CP-like functionality in non-mainframe
computers, sometimes with some level of initial success. Even early IBM
PCs had host-side DMA channels. But long term all such attempts
[outside of mainframes] failed. On the other hand, PP-like things are
successful. The distinctions between CP and PP are two:
1. Physical. Which side of I/O bus?
2. Responsibility. Who writes programs that run on this intelligent
processing element? OS and apps programmer (seen like the same in this
particular case) or device manufacturer? And on which level the whole
thing standardized? Internal instructions or bus transfers/packets?

I am not happy about 2nd part of my definition, but right now can't
formulate it better.