ATARI 8-BIT IN STEREO #3

By Frankenstein

Thanx to AlphaSys for all the information and schemes.

Let's first start with an overview of the stereo articles.

PART #1 (MegaZine #2)
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Described how to build a second POKEY (GUMBY) into your Atari 8-bit. This info was released by Chuck Steinman from DataQue.

PART #2 (MegaZine #3)
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Frankenstein explained about the practical side of the GUMBY upgrade and adds a stereo-mono switch. The new hardware registers are listed and there's something about "how to modify existing software for the stereo upgrade". On side two there's software to update "SoftSynth" and "World of Wonders".

And now the story continues..
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AlphaSys discovers that some programs doesn't work 100% with the stereo upgrade. Some programmers who thought they were clever used ILLEGAL addresses to control POKEY. They poke their values in the range of $D210 to $D2FF which normally are just "copies" of the LEGAL POKEY hardware registers.

The only solution to this problem is to completely disable the second POKEY, as it wasn't there.
To do this we only need one switch! Note that this isn't the same as the stereo-mono switch which was introduced in part #2.

Is it possible to have eight channels mono through the TV speaker with help of the second POKEY?? OFCOURSE!
We just have to MIX the output of our new pokey with the rest of the audio output in our computer.
For this we only need one capicator and one resistor! (I was amazed when AlphaSys told me this).

If you already add the stereo-mono switch you could add another switch to disable the upgrade. A better solution is to buy a new switch with THREE separate on/off combinations inside (or TWO if you leave out the LEDs).

ON position
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stereo on (POKEY=left, GUMBY=right)
LED indicator on
second pokey enabled (TTL -> A4)

OFF position
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stereo off (POKEY=left AND right)
LED indicator off
second pokey disabled (TTL -> ground)

You can find the schemes together with the "AlphaSys scheme draw" program in an archive on side two.


SAVE THE POKEYS!
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We have to take good care of the spare parts of our Atari "classic". Ofcourse we don't want our POKEYs to die out.
Please don't do it the Chuck Steinman way. Don't cut the pins!
One better solution (but still dangerous for the old POKEY) is, to cut of pins of an IC socket and put it on top of the old POKEY. This way you save the pins of both POKEYs.

The best way is to make a plug-it-in board with TWO sockets for POKEYs. Just lift the old POKEY out of the old socket (if it's in a socket!) and stick the board into the old socket.
This is a problem when your POKEY is not in a socket (most aren't). In that case we have to remove the POKEY and place a socket in its place.
If you aren't an experienced solderer, please DON'T think its easy and you can do it anyway!
At least you need "solder sucking" equipment for that job. Without such equipment it's almost impossible to un-solder the POKEY.
If you don't know anybody with soldering experience AND "solder sucking" equipment, the only thing you can do is to rudely cut all the pins of the POKEY, throw it away and buy two new ones (ofcourse in a different order, since POKEYs aren't available in every supermarket, so you have to live with a broke computer for quite a while).

STEREO UPGRADE DELUXE!
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It's ready! For everyone who doesn't want to figure it all out, I've made an easy to install stereo upgrade. If there are enough people interested, it could be sold SOON!

The "Stereo upgrade DeLuxe" includes:

- FOUR stereo channels (extra output)
- EIGHT mono channels (TV/Monitor)
- plug-it-in board
- stereo on/off switch
- stereo on/off indicator LED
- stereo left & right audio plugs
- pokey chip
- manual (English)

The upgrade has all the features described in the articles.
The installation is easy:

- remove the old pokey
- put the old pokey in the free socket of the upgrade board
- put the board in the free socket of the motherboard
- connect only FOUR wires

Ofcourse you also have to place the switch, plugs and LED indicator somewhere in the cover of your Atari.

To cover for the designers costs of the board layout, we need to buy a certain amount of boards. Therefore we have to know if there are enough people interested in this upgrade.

Write to:

Mega Magazine
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