Path: utzoo!utgpu!news-server.csri.toronto.edu!mailrus!tut.cis.ohio-state.edu!zaphod.mps.ohio-state.edu!swrinde!cs.utexas.edu!hp-sdd!ncr-sd!ncrcae!hubcap!mark
From: mark@hubcap.clemson.edu (Mark Smotherman)
Newsgroups: comp.sys.cdc
Subject: Re: CDC nostalgia
Message-ID: <8547@hubcap.clemson.edu>
Date: 29 Mar 90 21:45:28 GMT
References: <19286@shamash.cdc.com>
Distribution: usa
Organization: Clemson University, Clemson, SC
Lines: 36

I've been collecting information on I/O subsystems of historically
important machines (and recently published a paper on this in ACM
Computer Architecture News, Sept. 1989).  The CDC 6600 is one of the
machines I'm interested in, and I'd like to get I/O code examples.
Do any of you have old listings and would be willing to share with
me?  Ideally, I would like to have something like (for some early
OS version):

	example user program (assembly) code to request I/O
	(preferably, a disk seek and read of a random record)

	ppu 0 code to recognize request and assign ppu for transfer

	ppu code to recognize assignment

	ppu transfer loop (was the ppu read instruction synchronous
	I/O, or did the ppu have a polling loop for the device?)

	ppu code to transfer from local memory to global

	ppu code to post completion

	example user program code to handle completion

This is how I believe the OS and the machine worked; please correct
me where I am wrong.  Also, what kind of IOCS functions were placed
in the ppu's?  (I know ppu 0 ran the OS at first, but did the other
ppu's do code translation, editing, record searching, etc.?)

I'd also appreciate suggestions or help as to how to obtain similar
example I/O code from other machines.

Thanks!
-- 
Mark Smotherman, Comp. Sci. Dept., Clemson University, Clemson, SC 29634
INTERNET: mark@hubcap.clemson.edu    UUCP: gatech!hubcap!mark