Re: ELF Membership card program assembly and transfer using a TI 99/4A computer

Stephen Cass

If anyone is interested in *how* the TI99 4/A ended up with its weird architecture, one of the TI folks involved with of the TMS9900 chip wrote about it for my magazine:

And here's his sidebar specifically about the TI 99 4/A

I'm fond of the TI 99 4/A myself, it was the first computer I programed on!


On Mon, Jan 27, 2020 at 8:00 PM Martin Heermance <mheermance@...> wrote:
I bought TI 99/4a about 15 years ago so I could play Parsec and TI Invaders. I also wanted to show my kids what 80s era computers were like.

It was so close to being a great computer, but they goofed with their RAM architecture. The main bus only had 256 bytes of static RAM and the ROM on it. While the TMS 9918 had the bulk of the RAM which was supposed to be for video use, but they also used it for other purposes.

The TMS 9918 is still popular today because it's a snap to interface to both the Z80 and 6502. I imagine it could interface to the 1802 as well.

On Mon, Jan 27, 2020 at 3:59 PM ajparent1/kb1gmx <kb1gmx@...> wrote:
The TI 99//4 and 4a suffer from making the 16bit wide 9900 into a 8bit bus
and then storing the basic programs in Grom is a strange semi addressable
thing that to for a jump you need to send an address to it and then run sequentially.

The 99/4 is the very definition of slow.  Shame as I have a TI9900 board that makes
it look like its running in reverse.  But its has none of the misfeatures of the 99/4.

The Elf often suffers from running at 2 or less mhz when faster is well within
even the oldest parts ability.  A fast part at 6 or more mhz boogies and 4mhz 
is not all that bad.

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