Path: utzoo!attcan!uunet!jarthur!usc!zaphod.mps.ohio-state.edu!ncar!ico!ism780c!news
From: news@ism780c.isc.com (News system)
Newsgroups: comp.misc
Subject: Re: Punched Cards
Message-ID: <43548@ism780c.isc.com>
Date: 6 Jun 90 21:23:05 GMT
References: <12546@netcom.UUCP> <220@taumet.COM> <12573@netcom.UUCP> <898@nlsun1.oracle.nl> <1990May29.132631.2253@pdn.paradyne.com> <1990May30.065025.25861@diku.dk> <1990Jun1.211352.4749@unhtel.uucp> <5157@stpstn.UUCP> <124@bohra.cpg.oz> <8119@ubc-cs.UUCP>
Reply-To: marv@ism780.UUCP (Marvin Rubenstein)
Organization: Interactive Systems Corp., Santa Monica CA
Lines: 19

In article <8119@ubc-cs.UUCP> buckland@cheddar.ucs.ubc.ca (Tony Buckland) writes:
>                          Deep in my memory is a recollection
> that some IBM machines, possibly 7090s, had an instruction
> that would load 24 words in binary mode from one card into
> memory and then begin execution with the first word.  This was
> the first step in bootstrapping (the 24-word program said
> "load a whole bunch more stuff and execute *that*").

The 709 (7090 and 7094) all had a LOAD-CARD button on the operator's console.
This button started the I/O channel and caused 3 words to be read into
locations 0, 1 and 2.  As soon as these three words were into memory (and
before the fourth word arrived), the word a location 0 was sent to the
channel as an I/O command and the CPU started executing at location 1.  For
the normal boot card, the first word directed the channel to read the
remaining 21 words into memory.  The second word on the card (the first CPU
instruction) was a branch to self if channel is busy. The third word was the
first instruction of the boot loader.  We don't need no stinkin boot ROM :-)

   Marv Rubinstein