TI 990 architecture / was Re: TI-99/4A Floppies

[Allison]

>
>Subject: Re: TI 990 architecture / was Re: TI-99/4A Floppies
>   From: "Liam Proven" <lproven at gmail.com>
>   Date: Tue, 02 Oct 2007 20:18:00 +0100
>     To: "General Discussion: On-Topic Posts Only" <cctech at classiccmp.org>
>
>On 02/10/2007, Allison <ajp166 at bellatlantic.net> wrote:
>
>> The 9900 chips is not crippled, for 1976 three voltage NMOS its about as fast
>> as the technology of the time could go.  The TI99/4 did however do a nasty to
>> it. One is they muxed the bus down to 8bits wide and that does slow the system
>> some. There were 128 words of ram (6810s) that if you execute there the speed
>> is noticeable.  The other is the GROM (sort of an interpreted language with a
>> register point to next instruction) is a bottleneck as well.  There was a
>> later 9980 and the 9985 which were a 8bit bus interface and were somewhat
>> crippled but I'd never seen one in a TI99/4A.
>
>That's probably true, but the 99/4a wasn't a 1976 machine. It was
>released in 1981 and withdrawn 1983. A bit unfairly for a tweaked 1979
>machine (the 99/a), the 99/4a's competition was mainly 1982 machines
>like the Commodore 64 and Sinclair Spectrum, which (based on my
>possibly erroneous recollection) outperformed the 99/4a significantly.

>The TI99/4 did however do a nasty to
>> it. One is they muxed the bus down to 8bits wide and that does slow the system

I requote the statement.  Why?  Because thats what I'd said.  The basic 9900 
chip was fairly fast the 99/4 computer is _not fast_ and I gave the reasons why.
Comparing it to 1980 tech just showed how badly the little console faired.
Having a 9900 system without the funky 99/4 hardware I can say the 9900 was
still not fast but faired far better against its contemporaries.  The reason 
it did well enough is the archetecture was very good even if 2mhz was somewhat 
slow.


Allison