USD $131.99

The ultimate upgrade for the original Atari 800 computer!

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SKU: INCOGNITO800FJC Categories: ,


The ultimate upgrade for the original Atari 800 computer!

Feature list:

  • 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)


Installation Instructions:


Opening your 800

This is quite easy. All you need to do is remove the trap-door, all the expansion cards that you have inside (this includes all three RAM carts plus the Personality/ROM board. After this, you”ll have to turn the unit upside-down and unscrew 5 screws in the corners, and in the middle of the front edge. Now you’re able to open the case – lift the top of the enclosure just enough to get a hold on the keyboard ribbon – disconnect it from the backplane – please take a closer look at how it is connected – ribbon has a plug wider than the connector on the backplane (motherboard) and you”ll have to connect it back just the way it was when reassembling the unit. Now, since you have a clear view of the power board and aluminum casting covering most of the backplane, disconnect the internal speaker and remove the whole casting with all that is connected to it from the case. You’ll find loads of screws to be removed on the bottom side of the cast holding an aluminum plate to the top part. After this, disconnect the 4 pin header leading from the backplane to the power board, and try to separate the casting from the backplane – it will come off with the power board, but this is the way it should be. Now the aluminum plate – it holds to the PCB by 4 expansion plugs – they are made from two parts – one is a pin that was inserted in the collar that expanded and made connection permanent, you need to use a small flat-headed screwdriver to push it all the way out, so you”ll be able to remove the collar. What you should have now, is the backplane PCB together with the CPU board and the plastic part that forms cartridge slot covers and expansion cards compartment. To get rid of it you”ll have to gently pry and push four snap-ins you find accessible on the bottom of the backplane PCB. Since you already have all that was required separately, you may proceed with the installation.

Readjusting the cutout

It is nice to have the Personality slot opening a bit wider than it is originally, so you can pass ribbon cable and auxiliary connectors cables freely. Please see the picture for the details. Some might think it is not the best idea, but this way nothing gets compressed as it will be reassembled and the chances of getting something short-circuit are almost nil.


Jumper wires

You”ll have to make two jumper connections on your board (see the pictures) – one connects REF signal from memory slots to the not used pin on personality slot – and this is essential for emulated MMU chip on Incognito board other is a jumper between RNMI and COLD-RESET pins, so that CPU would be in a known state when the board is re-installed. Remember that 400/800 had no real RESET, instead, it had a Request NMI line (sometimes referred as to RESET NMI) that did some kind of software reset – as this was OK for 400/800 system when ROM was connected to the system bus permanently, it”s not acceptable for XL/XE when you can disconnect ROM by writing to PORTB. BIOS will handle the RESET vector and redirect the CPU to the valid location instead.


Making connections for auxiliary header P5. This is essential for true XL/XE compatibility, as there are signals you need to tap in that are not present anywhere else in the system. These are:

  • pin #1 – HALT – necessary for ANTIC extended memory access (so-called CompyShop mode)
  • pin #2 – IRQ – required by some PBI devices
  • pin #3 & 4 – RD4 and RD5 – controlling cartridge port in XL/XE series (mandatory)
  • pin #5 – RNMI – that becomes our RESET line (mandatory)
  • pin #6 – RDY – another signal required only by some PBI devices

Please see the picture for tapping points for all these signals. Additionally, you may want to replace RD4/RD5 pulldown resistors with something ranging from 1.5k to 2.2kOhms. It will improve compatibility with cartridges, as protection resistors on Incognito board form with an original ones voltage divider that may render some carts unusable.




ATR change button, HDD activity LED, connector P6

If you want to use these features, you”ll have to make some readjustments to the power board – this way you won”t have to drill any ugly holes in your 800 case, instead it will be as discreet as it can be – after this, your light conductor just under START button becomes another button, just for cycling mounted ATR files, and it still serves it purpose as power indicator plus hard disk activity indicator.P6 pinout goes as follows:

  • pin #1 – HDD LED anode
  • pin #2 – HDD LED cathode
  • pin #3 – switch

To accomplish this, follow the pictures.






Replacing 74LS42 with ribbon cable

You need to remove the 74LS42 chip (location Z101) and replace it with the ribbon cable that was included in the kit. Fold the cable as shown.

Putting everything back together

Now you should have everything prepared for the Incognito board, all you have to do is to reassemble your unit. Start with taking the ribbon and the P5 and P6 header cables through the opening you cut in the plastic part of the expansion boards compartment. When you are done, put the compartment back in its place – it should snap back in and stay firmly attached to the PCB. Now proceed with the aluminum plate. Align it so holes in PCB match holes in the plate, and then put the expandable collars in those holes. When you put the first one take that pin you’ve was taken out of it, and put it back – this will fix the plate and easier the align of remaining holes. When completed you should reassemble the casting with the backplane PCB – just don”t start screwing it tight again, as it will be better if you check everything up before you do that. Install the Incognito board in the first slot (the one that was occupied by the ROM board) and turn the unit on – the Incognito BIOS screen should show up. If it doesn’t – recheck all your connections, especially those two jumper wires and RD4/RD5/RNMI lines. Please make sure you didn’t short circuit anything during the reassembly, as shorting any pin directly to one of the power rails (5V -5V or 12V) will kill it instantly

VISIT FJC`s PAGE to read about the firmware :

Additional information

Weight 6 oz
Dimensions 8 × 4 × 1 in


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