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From: Peter Flass <peter_flass@yahoo.com>
Newsgroups: alt.folklore.computers,comp.os.linux.misc
Subject: Re: The "Good" Old Days - Complete Specs for DX-10 Operating System
Date: Wed, 2 Oct 2024 18:07:20 -0700
Organization: A noiseless patient Spider
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John Ames <commodorejohn@gmail.com> wrote:
> On Wed, 2 Oct 2024 03:18:23 -0400
> "186282@ud0s4.net" <186283@ud0s4.net> wrote:
> 
>> The 990 series used the TMS-9900 chip and near variants. This was an
>> odd chip - kept the CPU registers out in ordinary RAM and could
>> switch quickly between different sets of registers. At that time, the
>> external RAM and CPU kinda ran at the same speed so little was lost
>> putting the registers in RAM.
>> 
>> I remember fooling with this chip on a TI-99/4a home computer (which,
>> tragically, horribly under-used the neat new 16-bit CPU). There were
>> ASM commands for dealing with the register, 'context', shifting. By
>> that means many users with their own space could be implemented
>> directly with the hardware.
> 
> I've always found the 9900 concept interesting, although its core
> assumption about memory speed doesn't really hold up today; much of the
> architecture was eventually reincarnated in TI's MSP430 series micro-
> controllers, but they ditched the memory-resident register file. But
> for the time, context-switching certainly didn't get any faster than
> that; only three actual registers to save, but you still got a
> comfortably PDP-11ish environment from the programmer's perspective.
> 
> But yes, it's astonishing just how bad the TI-99 design was; a cascade
> of bad decisions that turned what could've been a real contender in the
> home-computer wars into an absolute joke. One of my oneathesedays
> projects that I've toyed with for years (though never made any headway
> on) is to roll up a homebrew system that does right by the concept...
> 
>> How it is now AIN'T how it always was.
> 
> And may it never be forgotten ;)
> 
> 

We had one early, but mostly for games. i thought they had great games for
the time. #1 daughter wrote her first program in TI BASIC, the start of her
career. I never did much because I though the cassette interface sucked,
although it was probably about average back then.

-- 
Pete