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Welcome to the comp.sys.atari.8bit newsgroup!
Atari 8-Bit Computers
Frequently Asked Questions List
___________ _______________
| ///////// | _____________ | ||||||||||| |
|___________| | | | ||_______|| |
|______/////| |____[---]____| | / _________ \ |
|LLLLLLLLLLL| |LLLLLLLLLLL || | LLLLLLLLLLL L |
|LLLLLLLLLLL| |LLLLLLLLLLL || | LLLLLLLLLLL L |
|__[_____]__| |__[_____]____| |___[_____]_____|
130XE 800XL 800
___________ __---------__
| ///////// | | / _____ \ |
|___________| _____________ | / |_____| \ |
|______/////| |____[---]____| | ___________ |
|LLLLLLLLLLL| |LLLLLLLLLLL || | ========== =|
|LLLLLLLLLLL| |LLLLLLLLLLL || | ========== =|
|__[_____]__| |__[_____]____| |___[_____]___|
65XE 600XL 400
___________ _____________
| ///////// | ___________ | |
|___________| |/// / | | |
|______/////| |// / | /\___________ |=============|
|LLLLLLLLLLL| |/O\ |\/ |LLLLLLLLLLL| | LLLLLLLLLLL |
|LLLLLLLLLLL| |-----------| |LLLLLLLLLLL| | LLLLLLLLLLL |
|__[_____]__| |____O_O_O_O| |__[_____]__| |___[_____]___|
800XE XE Game System 1200XL
Additions/suggestions/comments/corrections are needed! Please send to:
mailto:hunmanik@earthlink.net
Copyright (c) 1992-2004 by Michael D. Current, and others where noted. Feel
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* *
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UPDATES SINCE PREVIOUS POSTING
2004.03.31 8.1 updated to Revision 1.9 (2004-3-30), thanks Freddy Offenga
------------------------------
Subject: 0.1) Table of contents
0.1) Table of contents
The Computers
1.1) What is an Atari 8-bit computer?
1.2) What is the Atari 400?
1.3) What is the Atari 800?
1.4) What is the Atari 1200XL?
1.5) What is the Atari 600XL?
1.6) What is the Atari 800XL?
1.7) What is the Atari 65XE?
1.8) What is the Atari 130XE?
1.9) What is the Atari 800XE?
1.10) What is the Atari XE Game System?
1.11) What are the 6502, ANTIC, CTIA/GTIA, POKEY, and FREDDIE chips?
1.12) What is the internal layout of the 8-bit Atari?
1.13) What issues surround NTSC vs PAL versions of the 8-bit Atari?
1.14) What are the pinouts for the various ports on the Atari?
Video Display
2.1) What video display devices can I use with my Atari?
Mass Storage
3.1) What are the Atari 410, 1010, XC11, and XC12 Program Recorders?
3.2) What other cassette recorders can I use with my Atari?
3.3) How do I run a program from cassette?
3.4) What are the Atari 810, 815, 1050, and XF551 Disk Drives?
3.5) What other floppy disk drives can I use with my Atari?
3.6) What kinds of 5.25" floppy disks can I use with my Atari drives?
3.7) What can I do to extend the life of my floppy disks?
3.8) How can I use a hard drive with my 8-bit Atari?
Printers
4.1) What are the Atari 820, 822, and 825 Printers?
4.2) What are the Atari 1020, 1025, 1027, and 1029 Printers?
4.3) What are the Atari XMM801 and XDM121 Printers?
4.4) What other printers can I use with my Atari?
MODEMs
5.1) What are the Atari 830, 835, 1030, XM301, and SX212 Modems?
5.2) What other modems can I use with my Atari?
More hardware
6.1) What is the Atari 850 Interface Module?
6.2) What is the Atari XEP80 Interface Module?
6.3) What accessories did Atari produce for their 8-bit computers?
6.4) What "vaporware" computers/peripherals were never released?
6.5) What are the power requirements for my Atari components?
6.6) What graphic tablets were produced for the Atari?
6.7) What lightpens were produced for the Atari?
6.8) What lightguns were produced for the Atari?
6.9) What paddles were produced for the Atari?
6.10) What voice/sound synthesis hardware was produced for the Atari?
6.11) What sound-digitizers/samplers were produced for the Atari?
6.12) What sound-enhancement upgrades were produced for the Atari?
6.13) What MIDI enhancements are there for the Atari?
6.14) What graphics enhancements are there for the Atari?
6.15) What types of memory upgrades are there for the Atari?
6.16) What networking hardware is there for the Atari?
6.17) Can I attach an ISA card to the Atari?
6.18) What preventative maintenance can I do on my Atari system?
Core software: OS, BASIC, DOS, Modem handlers
7.1) What versions of the Atari Operating System (OS) are there?
7.2) What is the ATASCII character set?
7.3) What is Atari BASIC?
7.4) What are Atari DOS 1, DOS 2.0S, DOS 3, DOS 2.5, and DOS XE?
7.5) What are MyDOS, SpartaDOS, and other popular DOS versions?
7.6) How do I modify Atari DOS to support more than two drives?
7.7) Are there Graphical User Interfaces (GUIs) for the Atari?
7.8) What should I know about modem device handlers?
Software
8.1) What programming languages are available for the Atari?
8.2) What cartridges were released for the Right Slot of the 800?
8.3) What games support 4 or more simultaneous players?
8.4) What programs run only on the 400 and 800 models, and why?
8.5) What programs make use of the Light Gun or a light pen?
8.6) What programs have a track ball mode or support a mouse?
8.7) What programs have a paddle(s) or Koala Pad mode?
8.8) What programs have a CX85 Numerical Keypad mode?
8.9) What programs have a Touch tablet mode?
8.10) What kinds of RAMdisks can be set up on the Atari?
8.11) What programs support a RAMdisk?
8.12) What programs require a RAMdisk?
8.13) What voice/sound synthesis software is there for the Atari?
8.14) What programs support stereo and upgraded sound?
8.15) What games support online action via modem?
8.16) What programs support Atari computer networking?
Working with Atari files: Compression, File formats, Copying
9.1) How can I work with .arc files on my 8-bit Atari?
9.2) What file formats for entire disks/tapes/cartridges are there?
9.3) How can I copy my copy-protected Atari software?
Interoperating with "modern" computers
10.1) What programs can log in to other computers via modem?
10.2) What programs can I use to host a BBS on the Atari?
10.3) How can I read/write Atari disks on an MS-DOS PC?
10.4) How can I read/write MS-DOS PC disks on my Atari?
10.5) How do I transfer files using a null modem cable?
10.6) How can my Atari use my PC's HD using SIO2PC or Atari810?
10.7) How can my Atari use my PC's HD, printer and modem using APE?
10.8) How can I connect my 1050 drive to my PC with the APE ProSystem?
10.9) What about interoperating with the Apple Macintosh?
10.10) Are there 8-bit Atari tools for the Commodore Amiga?
Timeline
11.1) How did Atari get its name?
11.2) What is the History of Atari?
------------------------------
Subject: 1.1) What is an Atari 8-bit computer?
Based in Silicon Valley in the U.S.A., the company known as Atari produced
a line of home computers from 1979 to 1992 often referred to collectively as
the "Atari 8-bits," the "8-bit Ataris," the "400/800/XL/XE series," etc.
The computers included the 400, 800, 1200XL, 600XL, 800XL, 65XE, 130XE, 800XE,
and the XE Game System.
These machines competed in the marketplace most directly with the likes of the
Commodore 64 series, the Apple II series, the Texas Instruments TI99/4A, and
the Radio Shack Color Computer, among others. Of these, the 8-bit Atari is
most similar to the Commodore 64.
In marketing their computers to the public, Atari always had to contend with
their company history and reputation as a maker of video games. While the
8-bit Atari computers in their heyday were technically quite comparable if not
superior in the worlds of home and business personal computing, they also live
up to the name "Atari" with a huge library of video games which were often
outstanding for their time.
The 8-bit Atari computers do not use the same cartridges or floppy disks as
any other Atari platforms, such as the 2600 Video Computer System (VCS), the
5200 SuperSystem, the 7800 ProSystem, or the ST/TT/Falcon computers. All of
these but the 5200, however, do share the same joystick/controller hardware
port.
The 5200 SuperSystem is actually nearly identical to the 8-bit computers
internally, yet cartridges for the 5200 and the 8-bit computers cannot be
exchanged, primarly due to the physically different cartridge ports.
Here are some of the performance specifications of the 8-bit Atari computers:
(Some of the rest of this section by Bill Kendrick)
CPU: 6502 (MOS Technology)
CPU CLOCK SPEED:
NTSC machines: 1.7897725 MHz
non-NTSC machines: 1.773447 MHz
SCREEN REFRESH RATE:
59.94 times per second (Hz) on NTSC Ataris
49.86 Hz on PAL machines
GRAPHICS MODES:
ANTIC CIO/BASIC Display Resolution Number of
Mode # Graphics # Type (full screen) Colors
---------------------------------------------------------------
2 0 Char 40 x 24 1 *
3 - Char 40 x 19 1 *
4 12 ++ Char 40 x 24 5
5 13 ++ Char 40 x 12 5
6 1 Char 20 x 24 5
7 2 Char 20 x 12 5
8 3 Map 40 x 24 4
9 4 Map 80 x 48 2
A 5 Map 80 x 48 4
B 6 Map 160 x 96 2
C 14 ++ Map 160 x 192 2
D 7 Map 160 x 96 4
E 15 ++ Map 160 x 192 4
F 8 Map 320 x 192 1 *
F 9 + Map 80 x 192 1 **
F 10 + Map 80 x 192 9
F 11 + Map 80 x 192 16 ***
* 1 Hue; 2 Luminances
** 1 Hue; 16 Luminances
*** 16 Hues; 1 Luminance
+ require the GTIA chip. 1979-1981 400/800's shipped with CTIA
++ Not available via the BASIC GRAPHICS command in 400/800's.
GRAPHICS INDIRECTION (COLOR REGISTERS AND CHARACTER SETS):
Nine color registers are available. Each color register holds any of 16
luminances x 16 hues = 256 colors. (Four registers are for player-missile
graphics.
Character sets of 128 8x8 characters, each with a normal and an inverse
video incarnation, are totally redefinable.
PLAYER-MISSILE GRAPHICS: (byte height and OR corrections from Piotr Fusik)
Four 8-bit wide, 120 or 240 byte high single color players, and four
2-bit wide, 120 or 240 byte high single color missiles are available.
A mode to combine the 4 missiles into a 5th 8-bit wide player is also
available, as is a mode to OR colors or blacken out colors when players
overlap (good for making three colors out of two players!) Players
and missiles have adjustable priority and collision detection.
DISPLAY LIST INTERRUPTS (DLI's):
Screen modes can be mixed (by lines) down the screen using the Display
List - a program which is executed by the ANTIC graphics chip every
screen refresh:
All other screen attributes (color, player/missile horizontal position,
screen width, player/missile/playfield priority, etc.) can be ajusted
at any point down the screen via DLI's.
SCROLLING:
Fine scrolling (both vertical and horizontal) can be enabled on any
line on the screen.
SOUND:
Four voices of 8-bit pitch-resolution, 4-bit volume-resolution,
8-distortion sound can be produced. 2 voices (1 and 2, and/or 3 and 4)
can be combined to make 16-bit pitch-resolution. Also 4-bit volume-only
modes can be enabled for digitally sampled sound replay.
A fifth "voice" is produced by the internal speaker on Atari 400/800's
(for keyclick and buzzer) and in the XL's and XE's this was
(fortunately!) rerouted through the normal audio output, and the
keyclick can be disabled.
------------------------------
Subject: 1.2) What is the Atari 400?
Released along with the 800 in 1979, the 400 was the low-end model of the two.
The only 8-bit Atari with a membrane keyboard rather than a full-stroke
keyboard. One of the few 8-bit Ataris lacking a composite monitor port.
Originally released with just 8K RAM, but most were sold with 16K RAM. Atari
sold the Atari 400 48K RAM Expansion Kit, which required a little soldering,
to dealers only.
Only the 400 and 800 8-bit Atari models have four controller (joystick) ports.
Early 400 units include the CTIA chip; later units include the GTIA chip, also
present in all later 8-bit Ataris.
The 1982 Atari catalog calls the 400 "The Basic Computer."
The 400 was discontinued in 1983.
During development the 400 was known internally as "Candy."
------------------------------
Subject: 1.3) What is the Atari 800?
Released along with the 400 in 1979, the 800 was the high-end model of the
two. The 800 is the only 8-bit Atari with a Right Cartridge slot, in addition
to the Left Cartridge slot as present on all 8-bit Ataris. Originally
released with just 8K RAM, many were sold with 16K, later on 48K was standard.
The 800 is also the only 8-bit Atari with a four-slot modular design, where
the first slot holds the CX801 (CX801-P for PAL machines) 10K ROM module, and
the other three slots hold combinations of CX852 8K or CX853 16K RAM modules.
Jason Harmon writes: (12 Feb 2004)
"..the early ones had plastic cases on the ROM and RAM modules, and had two
thumb tabs to remove the cover to access the modules. Later model 800s had
48K standard, and to improve cooling Atari installed them without the cases
but put a small plastic strip across the tops of the cards to hold them in
position. These machines also lost the thumb tabs and have regular screws to
secure the cover over the memory slots."
Only the 400 and 800 8-bit Atari models have four controller (joystick) ports.
Early 800 units include the CTIA chip; later units include the GTIA chip, also
present in all later 8-bit Ataris.
The 800 was discontinued in 1983.
During development the 800 was known internally as "Colleen."
------------------------------
Subject: 1.4) What is the Atari 1200XL?
Released as a big brother to the 400/800 in 1982, the 1200XL now uses Atari's
slightly customized 6502C microprocessor, and includes a full 64K RAM. The
1200XL was the first 8-bit Atari with just 2 controller ports. In addition,
the 1200XL includes 4 programmable Function keys and a Help key, 4 LEDs,
built-in diagnostic and graphics demonstration programs, and probably the
favorite keyboard of any 8-bit Atari computer. Clicks previously outputted
through the built-in speaker are now heard from the television or monitor's
speaker. The revised 16K Operating System offers many new features, including
an alternate International Character Set.
The 1200XL was the biggest single step forward in development of the 8-bit
Atari platform, but the corresponding software compatability problems hurt its
popularity.
The 1200XL lacks separate chroma video signal, and also lacks the +5 Volts
power on pin 10 of the SIO port.
There is no PAL (European) version of the 1200XL.
The 1200XL was discontinued in 1983.
------------------------------
Subject: 1.5) What is the Atari 600XL?
Released in 1983 as a replacement for the 400, the 600XL is the low-end
version of the 800XL. The 600XL/800XL include most of the features of the
1200XL minus the Function keys and the demo program. But both the 800XL and
600XL have the Atari BASIC language built-in. In addition, these two systems
offer the Parallel Bus Interface (PBI), providing fast parallel access to the
heart of the computer. The 600XL has 16K RAM.
The 600XL can be expanded from 16K to 64K with the Atari 1064 Memory Module.
Rarely, some late-model 600XLs were sold with 64K RAM. These may have only
appeared in Canada. The box had a round gold foil sticker reading: "64k
Memory -- Now with a full 64k of memory built-in."
Normally boots with Atari BASIC (Revision B) enabled; Hold down [Option] on
startup to boot without BASIC.
The North American/NTSC 600XL does not include a composite monitor port; The
European/PAL 600XL includes the monitor port, but this lacks the chroma video
signal.
The 600XL was discontinued in 1985.
------------------------------
Subject: 1.6) What is the Atari 800XL?
Released in 1983 as a replacement for the 800 and 1200XL, the 800XL is the
high-end version of the 600XL. The 600XL/800XL include most of the features of
the 1200XL minus the Function keys and the demo program. But both the 800XL
and 600XL have the Atari BASIC language built-in. In addition, these two
systems offer the Parallel Bus Interface (PBI), providing fast parallel access
to the heart of the computer. The 800XL contains 64K RAM.
Normally boots with Atari BASIC (Rev. B, or late models with Rev. C) enabled;
Hold down [Option] on startup to boot without BASIC.
The 800XL lacks separate chroma video signal (exeception next paragraph).
There was a late version of the 800XL in Europe, called 800XLF. The 800XLF
includes a redesigned motherboard (the XE design) and contains FREDDIE for
memory management and has chroma output. BASIC is Revision C.
Though Atari never disclosed sales figures, the 800XL was likely the most-sold
of all 8-bit Atari computer models.
The 800XL was discontinued in 1985.
------------------------------
Subject: 1.7) What is the Atari 65XE?
Released in 1985 as a replacement for the 600XL, the 65XE is the low-end
version of the 130XE. The 65XE is nearly identical to the 800XL in features,
minus the PBI. Many European (PAL) 65XE's include the ECI port, but no North
American (NTSC) 65XE's include the ECI port. All XE computers also include
the FREDDIE memory management chip.
Normally boots with Atari BASIC (Revision C) enabled; Hold down [Option] on
startup to boot without BASIC.
The 65XE was discontinued in 1992.
------------------------------
Subject: 1.8) What is the Atari 130XE?
Released in 1985 as a replacement for the 800XL, the 130XE is the high-end
version of the 65XE. The 130XE offers 128K RAM, plus the FREDDIE memory
management chip, supporting the unique (but rarely used) ability for the 6502
and the ANTIC to independently access RAM banks. In addition, the 130XE
replaces the PBI port with the Enhanced Cartridge Interface (ECI), continuing
the powerful feature of a fast parallel port.
Normally boots with Atari BASIC (Revision C) enabled; Hold down [Option] on
startup to boot without BASIC.
The 130XE was discontinued in 1992.
------------------------------
Subject: 1.9) What is the Atari 800XE?
Unseen and unknown in North America, the 800XE was sold in eastern Europe. The
800XE is identical in features to the European version of the 65XE, including
the ECI port. The 800XE could also be described as a 64K version of the
130XE.
Normally boots with Atari BASIC (Revision C) enabled; Hold down [Option] on
startup to boot without BASIC.
Jindrich Kubec writes, "The problematic Chinese 800XEs with GTIA problems were
manufactured in 1992."
The 800XE was discontinued in 1992.
------------------------------
Subject: 1.10) What is the Atari XE Game System?
In a change of marketing strategy, Atari introduced the new XE Game System in
1987. Despite its label, the XEGS is a true 8-bit Atari computer system. It
offers the convenience of a detachable keyboard and built-in Missile Command
game, while offering 64K RAM and full compatibility with the 65XE. It was
packaged with the Light Gun, and the Flight Simulator II and Bug Hunt
cartridges.
Keyboard connected/no cartridge:
boots to Atari BASIC
Keyboard connected/no cartridge/[Select] held down at startup:
boots to Missile Command
No keyboard connected/no cartridge:
boots to Missile Command
No keyboard connected/no cartridge/[Select] held down at startup:
boots from disk drive
No keyboard connected/no cartridge/[Select]+[Start] held down at startup:
boots from tape drive
[Option] held down at startup = BASIC on
[Option] not pressed at startup = BASIC off
(opposite from all other XL/XE machines)
Andreas Magenheimer writes:
Tip: The confused XEGS Atarian should use the XEGS manager by Mat*Rat
(Mathew Ratcliff). This assumes one knows at least how to boot a disk
with the XEGS...
James Bradford offers:
There is only 1 32K ROM in the XEGS, it has the OS, BASIC (Rev C) and
Missile Command on it.
The XE Game System was discontinued in 1992.
------------------------------
Subject: 1.11) What are the 6502, ANTIC, CTIA/GTIA, POKEY, and FREDDIE chips?
Some of the following text is taken from De Re Atari (Atari#APX-90008), a book
published by Atari through the Atari Program Exchange (APX) and copyright 1982
by Chris Crawford, et al. See http://www.atariarchives.org/dere/ where the
full text of De Re Atari is now available online.
The internal layout of the Atari 8-bit computer is very different from other
systems. It of course has a microprocessor (a 6502), RAM, ROM, and a PIA.
However, it also has three special-purpose (LSI) chips known as ANTIC, GTIA,
and POKEY. These chips were designed by Atari engineers primarily to take
much of the burden of housekeeping off of the 6502, thereby freeing the 6502
to concentrate on computations. While they were at it, they designed a great
deal of power into these chips. Each of these chips is almost as big (in terms
of silicon area) as a 6502, so the three of them together provide a tremendous
amount of power. Mastering the Atari 8-bit computers is primarily a matter of
mastering these three chips.
6502 Central Processing Unit (CPU)
====
While the 400/800 models contain a generic 6502B CPU (a faster version of the
original 6502A microprocessor), all of the XL/XE models contain Atari's
customized 6502C chip.
On the Atari, there are two microprocessors, ANTIC and the 6502. To allow
them to coexist, ANTIC must shut off the 6502, a process called DMA. The
6502B supports DMA, but in Atari's implementation, it required 4 chips. The
6502C has an extra line called HALT. It is controlled by ANTIC which uses it
whenever it needs the data/address bus. The HALT line is on pin 35 of the
Atari 6502C and must be pulled high for the chip to work.
ANTIC
=====
ANTIC ("Alpha-Numeric Television Interface Circuit") is a microprocessor
dedicated to the television display. It is a true microprocessor; it has an
instruction set, a program (called the display list), and data. The display
list and the display data are written into RAM by the 6502. ANTIC retrieves
this information from RAM using direct memory access (DMA). It processes the
higher level instructions in the display list and translates these
instructions into a real-time stream of simple instructions to GTIA.
Frank Schuster writes (6/1/02):
the patent for the ANTIC processor:
U.S. Patent 4,296,476 October 20, 1981 for a "Data processing system with
programmable graphics generator". Inventors listed: Steven T. Mayer; Jay
G. Miner; Douglas G. Neubauer; Joseph C. Decuir
CTIA/GTIA
=========
CTIA ("Color Television Interface Adapter") / GTIA ("George's Television
Interface Adapter") is a television interface chip. ANTIC directly controls
most of GTIA's operations, but the 6502 can be programmed to intercede and
control some or all of GTIA's functions. GTIA converts the digital commands
from ANTIC (or the 6502) into the signal that goes to the television. GTIA
also adds some factors of its own, such as color values, player-missile
graphics, and collision detection.
Early 400/800 models included CTIA, later 400/800 models and all later 8-bit
Ataris included GTIA.
In BASIC, type POKE 623,64 [RETURN] and if the screen blackens, you have the
GTIA chip. If it stays blue, you have the old CTIA chip.
By the way, apparently no CTIA-equipped Ataris were shipped to Europe.
Clay Halliwell provides this tidbit:
A bit of trivia: CTIA 400/800s artifact in blue/green, GTIA 400/800s
artifact in green/blue, and all XL/XEs artifact in red/blue.
Jerry Jessop explains why French Ataris produce fewer colors:
I will tell you why it only has monochrome out, because it's SECAM and a
SECAM GTIA was never produced. The PAL GTIA is used in France and the Lum
outputs are run into an onboard encoder to produce a "psudo" color depending
on the Luminance output, composite only. This is why a SECAM VCS or 800 has
nowhere near the same number of colors (16) availible as a PAL or NTSC unit
(256).
The FGTIA was never completed as the market size did not warrant the
expense. The largest SECAM market is not France but the Soviet Union
(former) and in 80-84 sales of these items there were not possible.
Frank Schuster writes (6/1/02):
..here a summary of Atari patents covering technical parts of the GTIA /
CTIA or at least the steps of development to it. I found them by following
the references made in the "newest" patent 4,324,401 which at the end
stands for the GTIA.
U.S. Patent 4,324,401 April 13, 1982 for a "Method and system for
generating moving objects on a video display screen". Inventors listed:
David R. Stubben, Lyle V. Rains. References: 4,116,444; 4,107,665
U.S. Patent 4,189,728 February 19, 1980 for an "Apparatus for generating a
plurality of moving objects on a video display screen utilizing
associative memory". Inventor listed: David R. Stubben. References:
4,116,444; 4,045,789
U.S. Patent 4,116,444 September 26, 1978 for a "Method for generating a
plurality of moving objects on a video display screen". Inventors listed:
Steven T. Mayer; Ronald E. Milner. References: 4,016,362; 3,793,483
U.S. Patent 4,107,665 August 15, 1978 for an "Apparatus for continuous
variation of object size on a raster type video screen". Inventors listed:
Steven T. Mayer; Ronald E. Milner
U.S. Patent 4,045,789 August 30, 1977 for a "Animated video image display
system and method". Inventor listed: Stephen D. Bristow. References:
3,793,483
U.S. Patent 4,016,362 April 5, 1977 for a "Multiple image positioning
control system and method". Inventors listed: Stephen D. Bristow; Steven
T. Mayer. References: 3,793,483
U.S. Patent 3,793,483 February 19, 1974 for a "Video Image Control System
for Amusement Device". Inventor listed: Nolan K. Bushnell
POKEY
=====
POKEY (means "POT and KEY" as in the paddles and keyboard) is a digital
input/output (I/O) chip. It handles such disparate tasks as the serial I/O
bus, audio generation, keyboard scan, and random number generation. It also
digitizes the resistive paddle inputs and controls maskable interrupt (IRQ)
requests from peripherals.
All four of these LSI chips function simultaneously. Careful separation of
their functions in the design phase has minimized conflicts between the chips.
The only hardware level conflict between any two chips in the system occurs
when ANTIC needs to use the address and data buses to fetch its display
information. To do this, it halts the 6502 and takes control of the buses."
The USPTO granted U.S. Patent 4,314,236 to Atari on February 2, 1982 for an
"Apparatus for producing a plurality of audio sound effects" - POKEY.
Inventors listed: Steven T. Mayer, Ronald E. Milner
FREDDIE
=======
The 65XE/130XE/800XE/XEGS contain a small additional LSI called FREDDIE, a RAM
address multiplexer. According to James Bradford, "FREDDIE is a type of
memory controller. It takes the address and clock from the CPU and
multiplexes it with the appropriate timings and signals to use DYNAMIC memory.
FREDDIE also buffers the system clock crystal and divides it down then feeds
that to GTIA. The XEGS has a FREDDIE but it doesn't have the extended RAM.
Even if it did, you would still need the chip that does the REAL bank
switching. It is a small 16-pin chip (Atari/Best Electronics catalog number
CO25953: rev9/page 42). It gets RAS from FREDDIE, the bank select bits from
PIA, A14, A15 and the 6502 halt signal to control which bank of 8 chips RAS
goes to. A14 and A15 then go to FREDDIE for the address range of the extra
memory bank (or normal address range with no bank switching). The ANTIC/6502
select bits in combination with the 6502 halt line, control the switching of
the PIA bank number bits to A14/A15 and which bank of memory RAS goes to. Why
people say FREDDIE does the bank switching is beyond me. An 800XL can look
like a 130XE with that 16-pin chip installed (That's right NO FREDDIE) and an
extra 8 RAM chips."
And more recently James Bradford has written:
FREDDIE is just a memory decoder and timer. It replaces several chips in the
800XL. The small chip near FREDDIE does all the bank selection. CO25953. One
line from FREDDIE, Ras (or is it cas?) goes to this chip, Halt and the bank
/processor select lines go into this same chip and ras (cas?) comes out. A pin
for each bank. If I remember correctly, refresh also goes into this small
chip. It would be quite easy to make an 800XL work just like a 130XE with this
chip since Ras (Cas?) is required by ALL dynamic RAM.
======
Technical data sheets and schematics for the ANTIC, GTIA, and POKEY chips are
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