[sci.electronics] What micro in Intellivision video games?

colwell@mfci.UUCP (Robert Colwell) (05/15/89)

I'm looking at an Intellivision video game for a friend, ca. 1979, which
seems to only remember how to put out vertical and horizontal sync, but
nothing else.  I suspect the micro, but the manufacturer glued metal
heat sinks to the tops of the chips in question and I can't tell what
they are.  Does anybody out there know?

Bob Colwell               ..!uunet!mfci!colwell
Multiflow Computer     or colwell@multiflow.com
175 N. Main St.
Branford, CT 06405     203-488-6090

greg@bilbo (Greg Wageman) (05/17/89)

In article <847@m3.mfci.UUCP> colwell@mfci.UUCP (Robert Colwell) writes:
>
>I'm looking at an Intellivision video game for a friend, ca. 1979, which
>seems to only remember how to put out vertical and horizontal sync, but
>nothing else.  I suspect the micro, but the manufacturer glued metal
>heat sinks to the tops of the chips in question and I can't tell what
>they are.  Does anybody out there know?

As I recall, the Intellivision used a Z80 processor driving a Texas
Instruments TMS9918-A display controller.  This is the same graphics
chip that TI used in their 99/4 home computer, but without the
proprietary "GROM" (Graphics ROM).  This is a "sprite"-oriented
graphics chip with several display modes, and it managed its own DRAM
display memory.  The highest resolution it can produce is 256 by 192
with 16 colors from a fixed palette.  It generates a composite video
signal on-chip.  It is theoretically capable of mixing external video
into its display.

It is programmed via a two step, "register-select, data byte" scheme,
with an auto-incrementing address mode for block-loading the display
RAM.  The 9918 runs quite hot so the heatsink is a good idea.  I
believe TI came out with a high-temp version of this part sometime
later.

The 9918 has a number of limitations, including the ability to display
only 4 active sprites on the same scan line.  Any additional active,
lower-priority sprites are blanked.  The result is that in some
complex games, like "Donkey Kong", you will see some of the moving
graphics wink out and wink back on periodically.  There are also
limitations in the number of simultaneous colors you can get within an
8 by 8 pixel block.  All in all, it is a pain to program, but was a
fairly powerful part for the price.






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mmm@cup.portal.com (Mark Robert Thorson) (05/18/89)

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.

jimc@iscuva.ISCS.COM (Jim Cathey) (05/18/89)

In article <987@snjsn1.SJ.ATE.SLB.COM> greg@sj.ate.slb.com (Greg Wageman) writes:
>In article <847@m3.mfci.UUCP> colwell@mfci.UUCP (Robert Colwell) writes:
>>I'm looking at an Intellivision video game for a friend, ca. 1979, which
>>seems to only remember how to put out vertical and horizontal sync, but
>>nothing else.  I suspect the micro, but the manufacturer glued metal
>>heat sinks to the tops of the chips in question and I can't tell what
>>they are.  Does anybody out there know?

>As I recall, the Intellivision used a Z80 processor driving a Texas
>Instruments TMS9918-A display controller.  This is the same graphics

I thought the Intellivision used the General Instruments 1600 (??) series 
micro, a 10-bit PDP-11-oid.  I don't know if it used the 9918 or not.

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kencr@haddock.ima.isc.com (Kenny Crudup) (05/26/89)

FWIW, the numbers of the chips are located *under* the chips (on the wrong
side). I got a non-functional Ineptivision a few years back, and went as
far as to call GI for the FREE data book. They are heavy into custom chips.
One of the chips (I think the one on the far side turned sideways) is a 
pretty decent complex sound generator.

And yes, the GI 1610 is the worlds most screwed up processor. 10 bits.
Guess who'se 10-bit memories you had to use..... :-)

-- 
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...you ain't guarding the door, so what you need a gun for?
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