ken@hpclkms.HP.COM (Ken Sumrall) (10/15/89)
Here are the mods for the 600XL I mentioned a few weeks ago. Sorry to take
so long to post this to the net, but I had to remember how I did the mods.
(I seem to have lost the documentation I wrote down when I did these the first
time, and I had to open my 600XL and reverse engineer my own mods!)
Anyway, here are my mods for adding a monitor jack to a 600XL, adding a cold
reset switch to an XL or XE, and upgrading a 600XL to 64K.
I hope someone finds this stuff useful.
Ken "If it ain't modified, it ain't mine" Sumrall
ken%hpda@hplabs.hp.com
...!hplabs!hpda!ken
HOW TO ADD A MONITOR JACK TO A 600XL
THIS MOD IS COPYRIGHTED BY KEN SUMRALL. HOWEVER, YOU MAY FREELY
DISTRIBUTE IT, AND MODIFY IT, AS LONG AS THIS NOTICE IS INCLUDED
IN ITS ENTIRETY. THE AUTHOR MAY BE REACHED AT THE FOLLOWING
EMAIL ADDRESSES:
ken%hpda@hplabs.hp.com
...!hplabs!hpda!ken
Here are instructions on how to add a monitor jack to your 600XL. This jack
contains the following signals:
pin signal
--- -------------------
1 Composite luminance
2 Ground
3 Audio out
4 Composite video
5 Composite chrominance
The numbering convention for the DIN connector is:
3 o o 1
5 o o o 4
2
This mod for the 600XL provides every one of these signals except the
composite chrominance. (Actually, the 800 and the XE both supply
the composite chrominance signal, but the 800XL does not. Adding
the composite chrominance signal to an 800XL is a simple mod that
was described in ANTIC a few years ago. If you can't find the
mod, send me e-mail, and I will try and find it.)
COMPOSITE VIDEO (pin 4):
To add composite video to your 600XL, you need the following parts,
which are all available are Radio Shack:
(1) 2N2222 general purpose transistor
(1) 2.2K ohm resistor
(1) 3K ohm resistor
(1) 75 ohm resistor
(1) 5 pin DIN female connector
Here is the circuit diagram. It is a basic emitter follower circuit:
+5V
---
|
|
+--------------------------+
| |
| |
| |
\ |
/ |
2.2K \ |
/ Collector |
\ /-------+
| /
Signal In | Base |/
o-----------+---------------| 2N2222
| |\
| \ Signal Out
| \-------+-------------------->
| Emitter |
| |
\ \
/ /
3K \ \ 75 Ohms
/ /
\ \
| |
| |
| |
+--------------------------+
|
-----
---
-
I built this by just soldering the resistors and the transistor together,
and did not put this on any kind of circuit board. After you have built
this little circuit, you unsolder the 1st wire from the right of the
RF modulator as you look at it from the front of the computer,
and then solder that to the Signal In of this circuit.
You then connect the Signal Out line to the 1st terminal from the right of the
RF modulator, and also connect it to pin 4 of the DIN connector. You should
use shielded wire when you connect the Signal Out line to pin 4 of the
DIN connector. You can connect the ground wire to any major ground point
on the mother board. I hooked mine to the metal case of the RF modulator.
The +5V line is also available on the RF modulator. The 2nd pin from the
right of the RF modulator is the +5V power supply for the RF modulator.
COMPOSITE LUMINANCE OUTPUT (pin 1):
To add composite luminance (black and white signal only) to the DIN
connector, connect a 75 ohm resistor between the emitter of transistor Q6
and pin 1 of the DIN connector. You should use shielded wire to keep
noise from appearing on the line.
AUDIO OUTPUT (pin 3):
To add audio output to the DIN connector, connect a wire from the
2nd terminal from the left on the RF modulator to pin 3 on the DIN connector.
COMPOSITE CHROMINANCE (pin 5):
I have not found a simple mod to pick up the composite chrominance
signal for the DIN connector. I have not looked terribly hard, however,
since it is possible to use the composite video output as a composite
chrominance signal on many monitors. That is how my 600XL is hooked up
to my separate composite chrominance/luminance monitor, and it looks
great!
GROUND (pin 2):
I just connected pin 2 of the DIN connector to the metal box that the
RF modulator lives in. However, you should be able to hook this pin up to
any major ground point on the motherboard.
I was able to mount the 5 pin DIN connector on the back of my 600XL,
between the RF modulator and cartridge slot. It is a slightly tight fit,
but you can fit it if you are careful.
HOW TO UPGRADE YOUR ATARI 600XL TO 64K RAM
THIS MOD IS COPYRIGHTED BY KEN SUMRALL. HOWEVER, YOU MAY FREELY
DISTRIBUTE IT, AND MODIFY IT, AS LONG AS THIS NOTICE IS INCLUDED
IN ITS ENTIRETY. THE AUTHOR MAY BE REACHED AT THE FOLLOWING
EMAIL ADDRESSES:
ken%hpda@hplabs.hp.com
...!hplabs!hpda!ken
You will need the follow parts to perform this mod:
(2) 4464 RAM chip, 64Kx4, 150ns or faster.
Additionally, you will need chip pullers, a soldering iron, and 3 small
pieces of wire. I used wire wrap wire when I did this mod.
If the chips on your 600XL are socketed, you're in luck, otherwise, you need to
first unsolder the following chips:
(1) 74S32 location U18
(2) 74LS158 locations U5 and U6
(2) 4416 locations U11 and U12
and put sockets on the mother board in their place to make the job easier.
Now bend up pin 9 on the 74S32, and put it back in its socket on
the mother board. Bend up pin 3 on the 74LS158 in location U5, and put it
back in its socket. Also, bend up pin 10 on the 74LS158 in location U6,
and put that chip back into its socket. The last two chips you need to
change are the two RAM chips. Put the 4464 chips into the sockets at
locations U11 and U12 on the motherboard.
Now you need to install 3 wires to complete the mod. The first wire should
be connected between pin 3 of the 74LS158 at location U5, and pin 20
of the parallel bus on the 600XL. The second wire should be connected between
pin 10 of the 74LS158 at location U6, and pin 18 of the parallel bus.
The third wire connects between pin 9 of the 74S32 at location U18, and
pin 45 on the parallel bus. That's all there is to it.
HOW TO ADD A COLD BOOT SWITCH TO THE ATARI XL AND XE COMPUTERS
THIS MOD IS COPYRIGHTED BY KEN SUMRALL. HOWEVER, YOU MAY FREELY
DISTRIBUTE IT, AND MODIFY IT, AS LONG AS THIS NOTICE IS INCLUDED
IN ITS ENTIRETY. THE AUTHOR MAY BE REACHED AT THE FOLLOWING
EMAIL ADDRESSES:
ken%hpda@hplabs.hp.com
...!hplabs!hpda!ken
To add a cold reset switch to an Atari XL or XE computer, just connect
a normally open push button switch between pins 13 and 14 on the
cartridge slot. These pins are +5V and the cartridge present lines
respectively. Unfortunately, hooking up a switch to the CPU Reset line will
do no good, since the SYSTEM RESET switch on the XL is hooked up to that
line already, and it doesn't force a cold boot.
To use the reset switch, push and hold the SYSTEM RESET button already
built into your XL. Then, push and hold the new switch you installed.
Now let up on the SYSTEM RESET switch until the computer starts to boot.
As soon as the computer starts to boot, push and hold the SYSTEM RESET
key again. Now let up the the new switch you installed, lastly followed by
the SYSTEM RESET key. The computer will start to boot again. If you want
to boot without BASIC, you should hold down the OPTION key before you let
go of the SYSTEM RESET key for the last time. This may seem complicated,
but with a little practice, it becomes second nature. I mounted my cold
reset switch right above the SYSTEM RESET key on both my 600XL and 800XL,
and I can easily do this with one hand.
Here is a description of why this works. When you hit the SYSTEM RESET key
or turn on the XL or XE, the OS ROM performs a checksum of the cartridge area,
and if it doesn't match the last checksum it computed, assumes that someone
either inserted or removed a cartridge, and starts to do a cold boot
sequence, instead of a warm boot sequence. So when you hold down the
new switch, it pulls the cartridge present line to +5V, which forces the
hardware to disable the top 8K of RAM. Then, when the computer computes the
checksum of the top 8K of RAM, it computes that checksum of a non-existent
cartridge which should return random garbage, since no ROM is really present.
Since the checksum won't match the previous one, this will make the OS want to
perform a cold boot. You then force another cold boot when you let up on the
cold boot switch and press the SYSTEM RESET key again, so that the computer
won't boot assuming incorrectly that it has a cartridge inserted.
One obvious flaw in this design is that you can't force a cold boot if a
cartridge is really inserted. However, the only cartridge I own is
BASIC XE, and I can type "bye" to drop into the self test, and then
hit SYSTEM RESET to cold boot the system from the self test.