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My custom Atari 800CX : The upgrade and mod evolution from a stock 800



REWRITTEN AS OF 12/07/21. NOT QUITE COMPLETE  AS OF 12/11/21; just more pictures to add in. 



     This is my blog on all the upgrades, modifications and hacks that have turned a standard 800 into a machine that is still the original vision of Jay Miner's 'Colleen' 800 at heart, and still fully compatible, but includes advancements and upgrades that Atari and Jay never envisioned over 40 years ago. Not just internal upgrades, but port and case modifications too. And finally, a complete "restoration" as the computer case, as well as the cases of peripherals including the 410 and 810 all were badly UV damaged (retro-brite done twice with yellowing returning) and the brittle plastic has cracked or broken in places. Some of it as a direct result of all the handling and modifications, and accidents. This has been an on-going project for over 2 years. Started after the first retro-brite attempt.


So body work and a completely new paint job have been done, including other system matching peripherals and controllers. But my 800's face lift and make-over are not to the original colors of the 800 line. I instead decided to redo the look of my 800 in homage to the ill-fated 'IBM "ATARI" PC' that I fell in love with the look at first site, when I first saw the image of it. Of course shape of the 800 case is the same, but the colors are taken from the mock-up IBM PC in the picture directly below this paragraph. I have made minor tweaks better to my liking and taken some liberties of my own and extrapolated across my entire 800 "system." Images of the completely repainted and redone ATARI 800CX and peripherals are at end of this blog, after detailing the upgrades and mods with specs and pictures first, because it's what is on the inside that counts, and looks are only skin deep.





My new 800CX* includes:


Incognito board


features include:


  • 4 slots for OS separate for Colleen and XL/XE mode
  • 64k of FLASH for future GUI
  • 2 slots for BASIC/CARTRIDGE
  • build in, configurable PBI CF card storage (works as PBI in XL/XE mode, and through SDX driver in Colleen mode)
  • build in FAT32 loader (SIDE) with both ATR and XEX file handling
  • SpartaDosX
  • onboard RTC
  • 1MB Axlon compatible memory expansion for Colleen mode
  • 64k/320k/576/1088k total memory available in XL/XE mode
  • up to 52k of memory in Colleen mode (configurable)









Pokeymax 3


features include:

  • Quad Pokey
  • Dual SID
  • Dual PSG
  • Four channel Covox, with Paula style DMA
  • GTIA audio digital pass though
  • SIO audio mixing
  • PBI audio mixing
  • May be updated/configured via software on Atari
  • Larger 10M16 FPGA, leaving adequate resources for future enhancements
  • Spare 5V safe IO for future enhancements









Sophia 2




  • 100% compatible GTIA replacement
  • PAL/NTSC encoding
  • Independent RGB/YPbPr/VGA and DVI outputs
  • 480p/576p 3:2/5:4, 16 luminance levels for all Antic and GTIA graphic modes
  • 8 selectable DVI graphic modes from 2 color to 18-bit color onscreen
    1280x960 4:3
    1280x1024 5:4
    1344x960 14:10
    1440x900 16:10
    1536x960 16:10
    1600x900 16:9
    1704x960 16:9
  • 15 loadable 18-bit color palettes






PBI upgrade (DIY)


  • Edge connector for a true XL/XE physically compatible PBI port
  • Connects to PBI out on the Incognito board via ribbon cable internally







Dual-PIA board (DIY)




  • Allows 4 extra controller ports ( 8 total in Colleen (800) mode and 6 total in XL/XE mode)
  • Second PIA uses POT(paddle) pins 5 & 9 on the 4 new ports for PIA CA1&2 and/or CB1&2 signals for communication instead of analog controller signals from Pokey. 
  • Header for future expansion 
  • New controller ports will be external, via ribbon cables exiting underneath the 800 case to a dual-use 3D-printed Turbo Freezer/external controller port case. The Turbo Freezer 2011 connects to the PBI, ports will be beneath Turbo Freezer







Custom A/V and SIO port boards (DIY)


  • Stereo out headphone jack for Pokeymax audio out
  • Second SIO port (both ports upgraded for HSIO upto ~126K vs 19.2K single speed
  • Mono audio out RCA jack
  • Composite out RCA jack
  • S-video out mini-din jack
  • DVI out for Sophia 2 
  • Original internal RCA RF out re-purposed for Pokeymax 3 RCA digital audio out jack






LED RGB internal lighting & keyboard lighting (DIY)


  • Full rainbow of colors
  • Multiple flashing and fading color cycle settings
  • Choose a single color
  • Brightness and dimmer adjustments
  • Remote controlled




Other minor upgrades and modifications (DIY)


  • Complete recapping of motherboard and PSU board
  • Pal conversion with PAL CPU board, Incognito and new PAL crystal on mobo
  • All 74LS series IC's replaced with newer 74HC or 74F series
  • Keyboard repairs



External upgrades


Fujinet 1.0




The #FujiNet device provides the following services:

Device Description Notes
C (Cassette Drive) Loads CAS images. Under Development
D : (Disk Drive) Load floppy disk images from onboard MicroSD or networked TNFS server. Supports ATR, ATX, and XEX formats. Currently Working
R: (Modem) 850 Modem emulation, supports Type 1 Poll to load handler. Works with existing communications programs such as Ice-T, BobTerm, AMODEM, PLATOTERM, and BBS servers. Currently Working
P: (Printer) Printer output saved to PDF files downloadable from the device. Available Printers: 820, 822, 825, 1020, 1025, 1027, 1029, Espon 80, Okimate 10, HTML for copy/paste, GRANTIC Screen Printer. Example 822 Printouts (PDF): Text & Graphics. Currently Working
N: (Network) NEW networking device. #FujiNet configuration commands in place and working (WiFi, mounting, etc).


Currently working

Other SIO2BT Bluetooth Connection. Apetime Real Time Clock (NTP). SAM Text To Speech as a printer, voice output from #FujiNet to Atari (Video with explanationWAV File & SAM short video). MIDIMaze network gaming in progress (Video) Currently working



Turbo Freezer 2011




  •  1MB flash and 1MB battery backed RAM, both XL and XE adapter boards are equipped with a pass-through PBI connector (XE adapter also contains a cartridge slot)
  • Freezer function: stop/resume a program at any time, save/load snapshots to/from TurboFreezer RAM / ramdisk / disk / tape. Built-in, enhanced, debugger. Stereo Pokey systems are now supported, too.
  • Oldrunner mode: integrated OldOS
  • 512k battery-backed ramdisk, 100% PORTB compatible
  • CartrdigeEmulation: can use up to 960k flash and 384k RAM to run 8k, 16k and OSS carts. Supports new SDX (same banking as Ultimate1MB, up to 512k max.) plus "stacked" carts running from the CartEmu (so you can run SDX and MAC/65 from the TurboFreezer). Added AtariMax 8Mbit (1MB) compatible banking (up to 960kB) and new 8k + RAM banking (main 8k bank at $A000, optional 8k RAM bank at $8000).
  • PBI adapter case includes 4 controller ports for use with Dual-PIA upgrade above



The new look in homage to the 'IBM "ATARI" PC'






Tragedy strikes! While carrying different case parts to the painting area for clear-coating I dropped the 800's hinged cover for expansion and cartridge ports! The hinges break in half and a chunk breaks off of the lower right corner of the cartridge door! Spot repairs ensue, first the hinge assembly is disassembled and then super glue is applied to hold pieces in place. Then J.B. Weld is liberally applied to the hinges and underside of the cartridge door for strength, leaving "welds" as-is for greater structural integrity. Then J.B. Weld is applied to the crack on the door front, and smoothed to hide the crack. It looked better before I painted, but it is acceptable for the time being and I will pursue getting a new cartridge door to replace this one. below are the broken pieces and then showing them repaired. The repaired door with paint applied will be shown below in the "finished" final reveal.





System nearly complete. Still needed: paint touch-up, badges and name tags, raised letter on face plates detailed. close-up shots in final reveal.




Here is are all the main system pieces, minus the Fujinet and Turbo Freezer connected. 99% complete. I have to do some touch up on the Fuji badge on the 800CX and finish detail painting the controller jack numbers on the lower front panel, and a touch up here or there. More pictures to come, with the system fully powered, with LED lighting and all sides and angles.










*Custom eXtended line. I spent a long time coming up with a new designation for my 800, since it is anything but a stock 800 anymore, inside and out. I finally decided on "CX" since there are so many new features one letter just doesn't cover it (beyond the X for eXtended line since now it is compatible with XL/XE's). I came up with the idea while giving my repainted CX85 and repainted self-designated 'CX35' mouse (see blog on modifying a TRS-80 Coco analog mouse to the Atari). Why not 'XC' staying in-line with XL and XE machines? Because "XC" would imply that it was part of the eXtended Line/eXtended line Enhanced computers, but the 800 was prior to the extended line and is only compatible due to upgrades, not an official extended line machine stock that was then customized. Also because it matches the "CX" designation of my keypad and mouse.













  • Like 9


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Wow a lot of work there.

I think the white looks great, wondering how you did the keys, are they adapted from the XE or maybe the ST line, or just painted with transfers, be nice to see in a future Blog update.


Edited by Simply_Graham
  • Thanks 1
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1 hour ago, Simply_Graham said:

Wow a lot of work there.

I think the white looks great, wondering how you did the keys, are they adapted from the XE or maybe the ST line, or just painted with transfers, be nice to see in a future Blog update.


It's the original keyboard, all keys removed and painted individually with vinyl key cap labels ordered from Germany through Poly-Play. https://www.polyplay.xyz/News_1

The white keys have vinyl labels and the gray and blue keys have DIY labels. If it's not detailed in my blog, I detailed it in "What's new pussycat too" thread on Atari Owner's Club or in threads in the Atari 8-bit hardware sub-forum there. But I understand you were away for a while and there's a lot of posts to sift through...

Edited by Gunstar
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On 2/19/2022 at 7:29 PM, WhataKowinkydink said:

Just saw your avatar in a Ballyalley thread and found myself stumbling onto this project blog.  This thing looks beautiful - really nice work.

Thank you very much.

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