Path: utzoo!attcan!uunet!portal!cup.portal.com!mmm
From: mmm@cup.portal.com (Mark Robert Thorson)
Newsgroups: sci.electronics
Subject: Re: What micro in Intellivision video games?
Message-ID: <18474@cup.portal.com>
Date: 17 May 89 17:18:45 GMT
References: <847@m3.mfci.UUCP>
Organization: The Portal System (TM)
Lines: 19

It's a General Instruments chip.  The part number is 1601 or 1602.
The chip is a mutilated form of the pdp-11.  To cut down the size of
the mode and reg fields, certain addressing modes can only be used
from certain registers.  I believe they also threw out all the deferred
addressing modes.  (There was some kind of patent fight with DEC.)

The net result was that they cut out six bits from the instruction word.
What did they do with the free space?  Nothing.  GI sold 10-bit wide ROM's
to go with the CPU.

One of the programmers of the Intellivision told me the GI chip was the
world's most screwed up microprocessor architecture.  I disagreed, telling
him the Signetics 8X300 was worse.  He'd never heard of it, so I showed him
the description in the Signetics databook.  A few minutes later, he came
back laughing and agreed that the 8X300 was indeed the worst chip.

I doubt if you can get a replacement.  The GI chip wasn't too popular,
so there would be little incentive to make more of them or retain a supply
of replacement parts.