Atari 8-bit

Christmas 1982 I got my Atari 600XL computer.  Some time later I got the 800XL because I kept running out of memory.

I am trying to pick up where I left off...

Ok so I have a few projects going at once.  This 600XL ... I have removed the motherboard and the keyboard connection.  I have ordered an arduino for the keyboard to USB controller, and I am looking at a single board Windows 10 computer with the 40 pin GPIO so it can talk to the joystick ports, the SIO port and the cartridge ports.  May have to count pins before I buy anything.  So for that project I have removed the motherboard, desoldered the keyboard, joystick and SIO ports.  As soon as the mail gets delivered, it's a little soldering, a little programming, then boom, Windows machine in a 600XL.  I will detail that one with pics and stuff.

So the other project is with the 600XL motherboard.  The 600XL is based off of the 6502 processor along with I think POKEY for controls and GITA or something ... I'm not really sure.  And that's the point ... all of these chips are socketed, so I have ordered some breadboards and also some prototyping boards.  I will first mount the chips in a breadboard to see if I can get anything, next I will mount the sockets into a prototyping board.

I see that there is a project called the 1088XEL and I am tempted to just buy the motherboard and a kit.  And I may do that eventually with parts.  But for now I am just interested in getting my 600XL chips working on a prototyping board.  To do this I will remove the chips, then I will desolder the motherboard as much as I can, and recreate what I can.

600XL Motherboard

Ok, so I wrote down all of the numbers on all of the chips.  I will try to find a diagram so I can reference things appropriately:

Ok, I found an image on the Internet.  These are the same chip layout that I have, though my numbers are slightly different.    We will have to figure out how to number them:

1 - F 4050 BPC | QR 8230 | INDONESIA
2 - CA358E | RCA 327
3 - AMI 8312MEL | C014805-01 | C03069
4 - S+P8310*A+ | DM74LS08N
5 - PCA EP 8212 | C060472 D | Manilla
6 - Malaysia 8327A | 19T3340-00 | SN74532N
7 - 74LS138N V8307 | SB
8 - IMP 8320 CPA | C021697-31 | C Atari 1983
9 - 74LS138N V8308 | SB
10 - 74LS375N V8315 | SB
11 - SN74LS51NDS | M QQ8215
12 - C061618 | SHRP 8318
13 - S 8323 C | C014806-03
14 - S+P8310*A+|DM74LS158N
15 - S+P8310*A+|DM74LS158N
16 - TMS 4416 - 15NL | BP8319
17 - TMS 4416 - 15NL | BP8319
18 - S 8313 | P6520A | C014795
19 - AMI 8305 MBX | C012294B-01 | C03051
20 - S8325 | CN62504N | C062024-08 | C 1983 Atari
21 - NCR 2364-30 | F807250 N8321 | C06032A-29 | C Atari 1979
22 - M MC14051B | CPDSRQ8307
23 - M MC14051B | CPDSRQ8307

And now to do a little research on each one...

13 - CPU (Sally)
13 - GTIA
19 - POKEY
18 - PIA
12 - MMU
20 - OS ROM

...and that is where I went to sleep last night.

I have added all of the chips into VISIO as if they were network segments.  I hope to begin to try to interconnect them soon.  The board is hard to read with all of the resistors in the way, I am thinking of cutting one leg of everything so I can see it better.  No cutting until I'm positive.

Ordered some prototyping boards, they are on the way.

Here is a listing of the chips by what I am numbering them as, what they are numbered as on the board, and hopefully what they do.  That would be a good start.

I have tried all kinds of PCB design software.  They all want you to design circuits and then convert it to visual.  I don't want to do that, I don't really understand what I am doing quite yet.  I am reverse engineering, so I am using Visio since I wasted an entire day testing design software.

1 - (can't find my reading glasses)...

There are 11 capacitors on the board.  I will replace them with brand new ones since that is what people do to upgrade things anyway.  I am pretty sure that I can order sockets to match the chips and mount them into protoboard, and then connect the 11 capacitors into the proper paths.

I am considering what to do with the resistors, that is what there are by far the most of.  But not insurmountable.  I could even take the resistors one by one and desolder them and wire them in place on a protoboard.  But that would get out of hand.

Fortunately everything on the motherboard is numbered.

I am going to research the RF video connections and see what I can remove from the board.  I do not have any other type of video so I will have to do a composite upgrade to get myself to a barebones minimum.  But I think the RF is documented well enough, and the world has evolved.  I will take a hobby PC without having radio waves beaming through my organs, please.  I will desolder these components and store for parts.

The resistors seem to be in groupings, like for controller ports or along one side of a controller.  And the board is numbered.  I may be able to branch off sections like joystick ports and cartridge ports and consider those components to be secondary.  Since I am protoboarding, and I have seven 8x12 sheets of board, I may dedicate one board to a specific thing like joystick ports ... I just have to see what talks to what I guess.

I REALLY want to move the original power switch to the proto board.  I will buy some LEGOs to hot-glue the base around the live parts.

I am seeing that I may be able to consider a couple of different buses, instead of a rat's nest.  I see the interconnections on the schematics broken down better.  I definitely need to print off the schematics.

I wish there was an electronics store nearby.

There are other upgrades.  I most definitely want a few ... the kit with 1mb and a realtime clock seemed nice, and drive and boot options to be added later would be great.  I don't care if this sits inside a clear plastic bin and runs like that, I am not trying to make this one looks like a production machine.  My other computer, the 800XL, I want to remain stock.  The case for this 600XL and all of the ports and connectors will be in use with a sister project.

I have broken two of the resistors on the motherboard.  There are numbers for the parts, I will have to order replacements.  I do not know what some of these parts are - I guess that's the whole point of this project.  I have to order sockets.  There are 11 capacitors, I have to order those.  The transistors, I have no idea how much replacement ones would cost ... I may de-solder those and move to the breadboard.

There are a fair number of points with lettering but no component.  I will document these as missing below:







I will desolder the 5 transistors (?) and 11 capacitors and document the identifier and and markings on the part, set aside for prototyping.


Saturday morning, the soldering iron is hot before 9am.  I have to go drive Uber from 12-8pm so I wanted to remove the capacitors and document them this morning.  It took about 20 minutes and a LOT of trying to get the first cap out, and I ripped one of the legs out.  I am either not doing something right or they installed this board using something more like industrial welding.

I may consider cutting the components away and documenting them one by one.  I cannot see the identifier on the board otherwise.  I don't want to do it just to destroy it though, any more than it already is.  So let's try another cap.


C83 - 16v10uf
C102 - 3.5v 4.7uf
C103 - 3.5v 4.7uf
C100 - 3.5v 4.7uf
C101 - 16v 10uf
C115 - 16v10uf
C95 - 470uf16v

There are 5 things that look like capacitors but the connectors are on each end, and they are laying on their side.  This is where I get to learn what THAT is all about.

C64 - 22uf16v
C13 - 12uf16v
C6 - 22uf 16v
C1 - 22uf 16v
C44 - 47uf 10v

I had to use needle nose to pop the caps off, it was quite easy and quite destructive.  All caps kept for archival.

I am going to try to remove and document a few more pieces...

V1 - C061090 NDK - got this out in one piece, looks important (crystal?)
R43 - some sort of dial, if this is for RF video I can ignore it

Q1 - F2N | 3904 | ECB
Q2 - M2N | 3906 | EBCI
Q3 - M2N | 3906 | EBCI

mangled that last one, going to just rip the rest of these and document

Q6 - F2N | 3904 | EBC
Q4 - 233 | MPS | A55

A straggler ... the flat style cap?

C10? - 181K | KCK

Pretty much just resistors and diodes left.  Rather than document them all, I will trace down which clusters are a part of what pathway/bus/subsystem and I will document them/remove from the motherboard in clusters.

Overwhelmed with the number of resistors and diodes/whatever that are left, I may just rebuild the computer on protoboard as per the schematic and just cross-reference the motherboard as I go.

I am waiting on the mail, I have 5 sheets of 8x12 protoboard coming, my first ever breadboard kit is coming, and a few other small batches of supplies.  This is my introductory project.

I am looking at the schematics in the meantime, and I do think I will break down the build into smaller sections that I can work with independently, so I don't end up with an instant rat's nest with no room to expand.

I am wondering about the power supply.  I want this all to run on +5.5v.  I don't want to also have to supply +12v and -12v.  I need to find out what that is for and what my options are.  For now I am planning to buy a new power connector and hard wire it into my protoboard and power the entire thing as was designed.  If I can get rid of the =12v and -12v somehow I will.

I am going to need to take inventory for a prelim build, and place an order at an online electronics store.  I am also going to repair my original 6-post 2600 by doing a composite upgrade, and perhaps on my 4-post vader 2600 also.  I have to make sure to get enough parts.

C50, C51, C54, C55, c97, c98 are all small yellow spherical components, writing too small. to make out, will rely on schematics.

It looks like C72,71,70,69,63,68,67,77,76,62 are all in a row and feed the joystick ports.  Removed and discarded (crumbled) will rely on schematics for information.

One protoboard for joystick ports, cartridge slot, SIO port and keyboard connector.  I will call this the I/O board.  LOL just kidding, I will call it Travis.  Pokey and some other chips may live on the island of Travis.  I have not yet identified all of the socketed chips and their function and physical interconnections.  I have time before the parts arrive.  Will be reading up.


There seems to be an A bus and a D bus, and the power seems to be somewhat segregated (+5A and +5B) ... I need to color code everything.

Ground - Black
+5A - red
+5B - pink?
Bus A - green?
Bus B - blue?

I will make a row of pins at the edge of the different protoboards so I can interconnect them.  Travis, the I/O board, will be able to be left disconnected and an SIO2SD connected to the edge connector in its place for a more streamlined operation, but can be removed to operate in legacy mode.

I wish there was an electronics store I could go look at parts locally.  Sadly, no.  Time to shop online and choose a vendor.  I have heard good things about Best Electronics, I will see what is up with them.


ok, my protoboards came in.  8x12, not inches, my guess in centimeters.  lol.  Maybe one chip per board or something.  Or maybe I order something more realistic, like a great big breadboard.  We'll see.


I have emailed the Atari parts guy about a set of replacement sockets for the 23 chips I have pulled.  Also for a basic set of resistors and capacitors.  I will also need to come up with a solution for BusA and BusD.  BusA has 16 wires and BusD has 8.  I need to shop for a ribbon connector that can be pieced in and branched off from.  Or something.  I want two data buses.  I need them with standard connectors and short basic cables.  We'll see.

I still haven't identified what some of these chips do.  A lot of them though, I have a better understanding of.  I am going to order a great big breadboard and a boatload of cables.


I have been looking more at the chips.  I made little stands for the little breadboards and laid some out.  Starting to get a general idea.

I need to leave enough room for more memory.  There are two RAM chips, I have to look at the options and how to upgrade so I can leave room.  I want to do the original config at first, then perform upgrades, and I don't want to end with a rat's nest.

I have identified chips for GTIA, MMU, ANTIC, CPU - Sally, 2x RAM, PIA, POKEY, OS, BASIC, 2x keyboard controllers.  I see other chips on the diagrams and how to wire them, I just am not sure what they do.

I am getting a better idea of a layout.  RAM in the middle, surrounded on 4 sides by SALLY, GPIA, ANTIC and POKEY.  I need to understand how the RAM is accessed so I can isolate a memory area and better understand the motherboard components.

I am seeing pins for the ports that I can leave out for now.  I will start labeling the pins soon.

I am seeing nothing but +5v.  I am going to install the DC socket and 5.0 voltage regulator from a digital clock that I salvaged onto my protoboard and check the output.  That may be my new 600XL power supply.


old article on what these things are doing.  by things I mean chips.

I find it interesting that (A) Basic is wired in place where there could be RAM.  That seems like a simple enough upgrade.  (B-C) I am amazed at how little (prongs?) are dedicated to RAM and how many are dedicated to joystick controller connectors.  All of the connections coming through the two joystick ports (14 total) are direct to the controller - well, to the POKEY, I guess not directly to the 6502, so nevermind ...I guess it is starting to all make sense.  Some of these chips I have not identified have turned out to be controller chips or however you call them ... I am having thoughts on how to arrange things.  As an IT sysadmin I have had to design racks full of interconnected servers almost as complicated, I should be able to organize my thoughts and pull this off.

And what I am wondering is if I can pull the BASIC rom and add an appropriate RAM chip.  Like, literally.  Since it is an either/or in that one diagram, it would literally plug into the address space, therefore the processor prongs(?) therefore the same socket?  I will look into this option.  I understand that this was a "thing" back then to have a prom with a program on it, and I can see splitting OS and BASIC into two so that there could be just OS as a more limited function ... meh once I start typing it I can't say it right ... I can see just having the OS prom and using the other socket for RAM and going with the paradigm of assuming a disk drive and manipulating the autorun.sys to set up the environment from disk (slower) and not from PROM.  I may even go with no cartridge socket either if that means I can more readily address memory, and if I can assume that all cartridges can also be disk files?

I need to order that set of capacitors and some sockets, and I am sectioning off the "secondary" sections of the motherboard that I can skip for the initial build.  I should be able to see a READY prompt without having ports wired in.  I am not going to try to assemble completely at first, just enough to get power, crystal, chip and video out.  If I can set that up and not blow it all up, then I will be satisfied that I will be able to do this.


this guy has some upgrades I will probably get and add in, so I need to make sure I leave room.  I can find a nice clear plastic container at the dollar store, should be easy to mount a power connector and display port to the clear plastic.  Once I get my protoboard laid out I will measure and get a clear container.  I already have a hot glue gun so I am all set! LOL just kidding time to make some mounts.

Ok, I am about to order some electronics.  I will get sockets for all of the chips, I will get replacement caps for the 11 I identified on the motherboard, I see that the entire 16-channel A bus and 8-channel D-bus all have resistors to +5vA, and I will document some of the areas on the schematics and I will try to get a few dozen extra of each rating.  I have some basic wire I can cut and use as jumpers.  I have a DC power adapter and connector and a 5vdc voltage regulator and heat shield thing.  I will designate one end of the board to be "power in" and this board will by Gladys as in I'm Gladys got some power.  I will start building Gladys and continue with that section while I consider my chip locations.

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