Atari Ajax Floppy Disk Controller
(The little known Atari Custom made Smart Upgrade chip)

History:

When Atari Japan was Designing / Engineering the First Generation Atari ST Computer (Atari 520ST Computer with external Power Supply and external Floppy Disk Drive) back in mid 1985 era, they based the first series Atari 16 bit computers on the Motorola 68000 16 bit 8Mhz CPU, it supporting chips like the Motorola Multi Function Peripheral  (MFP) chip, and Atari Custom made ST Memory Management Unit (MMU), Glue (code named because it holds the ST System together), DMA (Direct Memory Access) and Video Shifter chips.  In 1985 one of the State of the Art Floppy Disk Controller chips was the Western Digital WD1772 720K SSSD / DSDD Floppy Disk Controller chip.  This is the ST Floppy Disk controller chip Atari Japan Engineering decided to use in the first Atari 520ST computer and all other Atari ST Computers right up the early 68000 16Mhz Atari TT Business Computers.

The subsequent Atari designed 68000 16 bit 8Mhz 1040STF, 520STFM, 1040STE, Mega 1/2/4, MegaSTE 68000 16Mhz and later 68000 32Mhz second generation TT Computers all used the same WD1772 Floppy Disk Controller chip to drive the ST SSSD or DSDD Floppy internal Disk Drive circuits over many years.  As time marched on, Atari Engineering was asked by Atari Marketing to the upgrade the stock Atari Top line TT Business Computers 720K Internal Floppy disk drives to the Newer (for that era) 1.44 High Density (HD) Floppy standard.  

Atari Japan Engineering challenge was to upgrade existing Atari TT Computers to the HD 1.44 Floppy Mechs without major circuit changes to the TT motherboards or major chip changes to on the TT Motherboards.  What was finally decided, was to use hand selected / tested WD1772 chips and over clock them (run them at a faster chip clock speed 8Mhz to 16Mhz).  The WD1772 chips were not originally designed run at the faster 16Mhz internal clock speed, but thru testing, some were found be able to run at the fast clock speed required for HD 1.44 Floppy operation.   With some TT TOS Operating System upgrades (New version TT TOS), New 1.44 HD TT Floppy Disk mechs and the Hand selected / Tested WD1772 chips, Atari was able to upgrade all older / early 16Mhz Atari TT’s and Newer 32Mhz TT’s computers to the HD 1.44 Floppy Disk standard.

Obsolete WD1772 Chip:

Years down line when the newer Atari MegaSTE and Atari Falcon computers were being designed, the old WD1772 chips were becoming obsolete.  Most Disk Controller chips of that era, were lucky to have a normal useful product life / run of 1 to 2 years at most.  Atari had been using the WD1772 Floppy Disk Controller chip in ST computers close to 7+ years.  Western Digital had not made any new production runs of WD1772 Disk Controller chips in years and could not be convinced to make a new run of that old Disk Controller chip.  To support the older Atari ST computer line, Atari had the VLS Chip Company get a license from Western Digital and make a small new production run of the older standard WD1772 Disk Controller chip in a VLS labeled chip package for Atari.

But the writing was on the wall.  Atari Engineering had to find a new ST Disk Drive Controller chip and do some ST Major chip set changes or whole new redesign on future Atari ST Computers in regards to the ST Floppy Circuit design.  What Atari Engineering came up with was a new custom made Upgraded / Smart Disk Controller chip which was backward and forward compatible on all older ST computers and fully compatible on Falcon computers and future ST computers.  That new smart chip is the Atari Ajax High Speed Floppy Disk Controller chip.  

Ajax Chip:

The New Atari Custom made Ajax Disk Controller chip is 100% pin to pin fully backward compatible with the older WD1772 chip on all older ST and other Computer and devices that use the WD1772 Floppy Disk Controller chip.  It is also a Smart Disk Controller Chip that can auto sense the input chip Mhz Clock speed and auto switch into the Newer HD 1.44 Floppy Mode standard.  So a new state of the art Atari Ajax Disk Controller chip can be plugged into the first 1985 Atari 520ST computer made and drive the ST 720K SSSD / DSDD floppy internal or external Disk drive Mech.  The same exact Atari Ajax chip can be plugged into the Floppy Disk circuit on the last state of the art Atari ST computer made, the 1992 Falcon 030 68000 16Mhz Computer and drive the Falcon 1.44 HD Floppy Circuit without any hardware changes.

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An active Polish developer nicknamed Zaxxon is the creator. Probably Pear knows about him.