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It is possible to have a "true" computer module for the Atari 2600 --
if
you are willing to use an old Acorn Atom computer as guts!
NOTE: Only experienced techies should attempt to follow the
modifications
suggested in this guide. Also, you must be proficient in 6502/6507
Assembly Language. Also note, this is a parody and is meant as a joke.
Please do not seriously consider creating a VCS computer using Acorn
Atom
as a base -- the Acorn Atom sucks!
Other than that, keep on reading! :)
The following chips reside inside the Atom:
(from the website:
http://www.users.globalnet.co.uk/~thoth/atom/atom.htm)
6502 Microprocessor
6847 Video Display Generator
2114 RAM chips
6522 VIA
8255 PIO
8271 Floppy Disk Controller
6854 Advanced Data Link Controller
Although the Atari 2600/VCS has a 6507 microprocessor, the 6502 is
largely
compatible. In order to connect the Atom computer to your VCS, you will
need to create a VCS-cartridge compatible connector to plug into the
VCS
cartridge slot.
A good place to start is at Radio Shack, where you can purchase the
necessary supplies to begin designing the VCS cartridge-to-Acorn Atom
connector.
Once you have done this, you need to write a short (but sweet)
operating
system that will be able to LOAD and SAVE programs from a Desktop Tape
Recorder. You should also spend some time writing a BASIC interpreter,
as
well as creating a BIOS for use by the VCS.
You will also need to modify the Atari VCS board to accept regular
"walkman" style headphones -- aproximately 5mm in diameter. There is
enough space on either side of the VCS Revision 8 or 16 boards to allow
for the upgrade. This upgrade will allow you to plug any Desktop Tape
Recorder into the VCS for saving programs to cassette tapes.
Once this is done -- usually on your 23rd or so lunch break -- you can
then begin to add an additional ROM chip to the VCS motherboard
(preferrably 8KB, enough to hold the BIOS you wrote earlier). Burn this
in
carefully, making sure to use the proper EPROM utilities.
Finally, make sure to paint your VCS blue, as we all know -- BLUE
computers run much faster! ;)
Once this is done, you should see the following screen upon powering up
your new VCS/Acorn Atom computer:
Atari Acorn Atom Computer
3769 Bytes Free.
Ready.
*
The Atari Acorn Atom BASIC language consists of the following built-in
commands:
CREATE SPRITE
Use this command to place a SPRITE on the screen (0-2).
MOVE SPRITE
Use this command to move a SPRITE on the screen (0-191,0-88).
ROTATE SPRITE
This command rotates your VCS sprite in 4 possible directons (0-3).
BYE SPRITE
This will make a SPRITE disappear (0; 1 makes to appear as a negative
image)
NO LINE
This will make the stupid "line" on the screen in some games vanish
completely (0; 1 makes the line appear as a negative image)
GRAPHIC MODE
This sets the graphic mode (0 is text; 1 is 192x88; 2 is 96x88; 3 is
64x48).
PRINT
This command will PRINT a word on the screen. Default argument is 0.
FOR
This will set a loop from 0 to 32767.
NEXT
This will increment a step within a FOR/NEXT loop by N value. N is
optional.
IF
This is a conditional command. IF something is true, THEN do it.
THEN
Part of the IF/THEN turnpike. Use cautiously.
GOTO
Branches program execution to a line or name specified. Example: GOTO
HELL
GOSUB
Branches program execution to a line or name specified. Example: GOSUB
TRACT
MEM
This command tells the user how much memory is left in the VCS.
Optional.
VCYCLE
This command will force a VSYNC refresh.
PLAYGROUND (On/Off)
This command will alternate between the playfield graphics and a
picture
of nothing. Usually just a blank, dark screen.
DEMO
This command will make the VCS cycle through "demo" mode, complete with
a
256-color horizontal rainbow.
READ
This command READs in DATA from DATA statements. Self-explanatory.
DATA
This command contains DATA elements, i.e. numbers, letters and values
READ
in by the READ statement. Example: DATA 1,2,3,"Atari","Rules my goat."
ATARI!
This command does nothing, really. All it does is make the programmer
look
cool.
REM
A REMark statement is ignored by the Atari Acorn BASIC interpreter.
This
allows people to insert comments into their code. Example: REMember the
Alamo!
RND
This is a built-in function that allows the Atari to process
pseudo-random
numbers. Example: X=RND(.85)
INT
This is a supplement to RND. Example: I=INT(RND(1)*35)+1
STOP
This pauses execution of a program until a CONT statement is issued.
CONT
This resumes program execution after a STOP command is issued. NOTE:
You
must immediately follow STOP with CONT, or else a "?WTF" command
error will result.
INPUT
This command takes user input from the keyboard and prompts the user
for a
sentence (or a letter/number). Example: INPUT "What is your name?";A$
OPEN #
This command OPENs direct file access to the Tape Recorder. Use file
channel 4. Example: OPEN #4,"myfile"
CLOSE #
This command CLOSEs direct file access to the Tape Recorder. Use file
channel 4. Example: CLOSE #4,"myfile"
PRINT #
This command writes to a file OPENed previously. Use file channel
4. Example: PRINT #4,A$
GET #
This command gets from a file OPENed previously (sequentially, one
letter/number at a time). Use file channel 4. Example: GET #4,A$
COLOR
This command sets the text color (0-127). Example: COLOR 15
FGCOLOR
This command sets the foreground color (0-127). Example: FGCOLOR 2
BGCOLOR
This command sets the background color (0-127). Example: BGCOLOR 10
PAGE
This command switches between pages in RAM. Useful in 1K chunks.
Optional operator specifies read/write compatibility. Example:
PAGE 2,1
That's all for now. Check out for details on the Atari Acorn Computer
at:
http://www.atariacorncomputer.com/
(note: this site does not exist)
Cheers!
Sincerely,
Paul Allen Panks (a/k/a "Dunric")
dunric@yahoo.com
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An Atari 2600 computer new
