T11 design WAS - Re: Inside old games machines, was: Re: Simulated CP/M-68K?

[Allison]

>
>Subject: Re: T11 design WAS - Re: Inside old games machines,was: Re: Simulated CP/M-68K?
>   From: "Ethan Dicks" <ethan.dicks at gmail.com>
>   Date: Tue, 19 Jun 2007 10:33:29 -0400
>     To: "General Discussion: On-Topic and Off-Topic Posts" <cctalk at classiccmp.org>
>
>On 6/19/07, Robert Borsuk <rborsuk at colourfull.com> wrote:
>> I've been loosely following this thread and never heard of a T11 from
>> DEC.  So good'ole  Google and Bitsavers saves the day, but it get's
>> me thinking.  Has anybody done any design's with this processor?
>
>Yes (see the thread where it appears in a few video games).  DEC used
>it as a PDP-11-instruction-set-compatible microcontroller.  It appears
>on a few peripheral boards (the RQDX3 comes to mind), and a few other
>places.

Falcon card (Qbus SBC), KXT-11 (programmable Qbus slave), The RQDXn 
(all versions) and also the HSC50.

I have one of the rare design guides and a good handful of parts both ES 
and production.

Allison


>
>For some real boots-on-the-ground history, we turn to Bob Supnik...
>
>http://simh.trailing-edge.com/semi/t11.html
>
>(I did not know about his T-11-based RT-11 box - I should ask him about it).
>
>> Why wasn't this processor used instead of the 6100?
>
>In what?  In video games?  the 6100 _might_ have been a competetive
>architecture when it was new in the mid-to-late 1970s, but as
>competition against an early 8-bit micro, not a 16-bit micro, which
>the T-11 is.  From looking at the Atari line at the time, it seems
>that they were positioning the T-11 against the Motorola 68000.
>Presumably there was some engineering or marketing or production
>reason to go with the T-11 over the 68000, but, as much as I like the
>PDP-11, I can't imagine what that would be.  Perhaps the $10/unit cost
>that Bob Supnik cites was favorable compared to, say, trying to go
>over 8MHz on a 68000, but that's mere speculation.  I know that at the
>low-point in the 68000 timeline, it was going for about $3 each in
>reasonable quantities, but I don't know where that curve compares to
>the $10 each for the T-11.

The 6100 was PDP-8 and the basic archecture is 4k addressing, 12 bit
words and not rom friendly so it was not a contender for rom intensive
applications.

>I'm not saying you _couldn't_ make a video game based on the IM6100,
>but it didn't happen to have been done, and would probably just end up
>as a demonstration of engineering prowess, not something that would
>have made sense from a business standpoint in 1976.

Exactly!  The 6120 was faster and incorperated the MEDIC (interrupt
and memory expansion similar to PDP-8) but still even at 4k paged
and 32k (plus 32k CP memory) it was awkward compared to most micros.


Allison