Improving the TI-99/4A

Improving the TI-99/4A

Post by Thierry Nouspike » Wed, 16 Jan 2002 07:10:24



Hi there,

This is to announce that I have now added a "do-it-yourself" section to
my website at http://www.nouspikel.com/ti99/titechpages.htm

You will find a do-it-yourself primer, a guide on how to open the
console, a summary of TTL pinouts, and several pages dealing with the
modifications themselves.

Some of which you may have already seen:
- Installing a second RS232 card.
- Powering the joystick port and/or building a PC joystick adapter.
- Replacing ROMs with EEPROMs, both in a card and in the console.
- Installing Jeff Brown's interrupt mod.

But I recently added two new pages:

- One deals with a modification to the Widget that makes the 3
cartridges available at the same time, under different GROM bases. I got
this idea from someone in the TI99/4A online user group, but now I can't
remember who (announce yourself for credits).

Here the trick was to design a circuit that would remember wich GROM
base was used last, so it can select the proper cartridge ROMs...

The URL for this one is www.nouspikel.com/ti99/widget.htm

- The other page deals with overclocking the console. Usually this is
done by changing the crystal, or installing a switch to toggle between
crystals. But I wanted to be able to switch speed via software.

So I replaced the crystal with two 3-state oscillators, whose
output-enable pins are controlled via the CRU. Works like a charm: by
simply toggling one CRU bit, I can switch between 3 and 4 MHz and the
TMS9900 doesn't miss a beat (nor a bit).

The URL is www.nouspikel.com/ti99/clockup.htm

I hope you guys find these pages usefull. Have fun hacking your
consoles!

             Thierry

 
 
 

Improving the TI-99/4A

Post by Tyler Van Tighe » Fri, 18 Jan 2002 15:39:28



> - One deals with a modification to the Widget that makes the 3
> cartridges available at the same time, under different GROM bases. I got
> this idea from someone in the TI99/4A online user group, but now I can't
> remember who (announce yourself for credits).

Was it my post on my Super Extended Basic cartridge with John Guion's
"Multi-Mod" that uses the TI's "Review Module Library" function??

Also thanks for your information on the internals and various hardware
projects for the TI-99/4A.  It's an excellent on-line resource for all TI
user's around the globe!!

Tyler Van Tighem

 
 
 

1. New and Improved TI-99/4A Shrine!

I have finally found the time to update the content and links on the
TI-99/4A Shrine.  Just a sampling of the resources you'll find:

- Technical information including do-it-yourself repair and upgrade tips
- The TI-99/4A Community Address book including names, addresses, phone
numbers email, and web addresses
- Information about and links to all available TI-99/4A emulators
- Links to every(?) available TI-99/4A resource on the Internet
- Screenshots, sound samples and startup screens for your "modern" computer

Check out the TI-99/4A Shrine at <http://www.geocities.com/Athens/7374/ti.html>

Your comments and suggestions are welcome!

John McDonnell

2. VFAT is not reentrant

3. FA: Brand New Hunt thr Wumpus for the TI-99/4 and TI-99/4a

4. Looking for 3D shape files

5. WANTED TI-99/4, TI-99/2, AND TI-99/8

6. Passwording a printer

7. WTB: TI-99/8, TI-99/2, TI-99/4

8. modifying creation date of a file.

9. TI-99/5, TI-99/4B, and all that mess