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From: jthomas@nmsu.edu (James Thomas)
Newsgroups: comp.arch
Subject: Re: 1620 (was Re: Odd word size?  Word size?  Word?  Definitely Odd.)
Message-ID: <217@opus.NMSU.Edu>
Date: 9 Oct 90 19:55:51 GMT
References: <270CB430.21156@ics.uci.edu> <1990Oct8.220412.25532@ns.network.com>
Sender: news@NMSU.Edu
Organization: NMSU Computer Science
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In-reply-to: ddb@ns.network.com's message of 8 Oct 90 22:04:12 GMT

In article <1990Oct8.220412.25532@ns.network.com> ddb@ns.network.com (David Dyer-Bennet) writes:

ddb> ......  The instructions lengths were different,
ddb> and the 1620 used fixed length instructions whereas I'm nearly certain
ddb> the 1401 had variable length.

Technically the 1620 instructions were 2, 7, or 12 digits long (remember BB
- Branch Back????).  The 14xx instructions were 1 through 8 characters.

ddb> .....   A  "record mark" was a character code
ddb> (2 digits) relevant to some (few) character string instructions.

Naw, the record mark was a single "digit" - C82 - used by the TR (Transmit
Record) instruction (op=31).  It was also findable via the BR (Branch
Record) instruction (op=45).  Then there was also the "group mark".  Both of
these were stolen from the 14xx, which got them from ???

ddb> ...
ddb> there was a version using the transmit record instruction that was
ddb> special because it moved through memory in the other direction
ddb> (transmit record going left to right instead of right to left).

310000800009, e.g.

ddb> This is weird; I remember instruction names, and I remember numeric
ddb> opcodes, but I DON'T remember assembler mnemonics.

26=TF (Transmit Field), 16=TFM (Transmit Field Immediate)

ddb> ...

Jim Thomas