|The AFDC2 floppydisk controller was the
first controller for industriel floppydrives with the standard 34 pin
was able to handle large drives with more than 40 tracks and more than 1 side without patching the disks. It instead loaded the standard
operation system from the disk and then only patched the contents within the memory of the computer. It therefor determined the current
configuration by reading the 2 switchblocks from the card which had to be set to the current drives connected. Then by reading the operation
system in the memory of the computer the software in the eprom started by reading the settings of the 2 switchblocks and then mofifgied the
parameters for the handling of the drives in the memory of the computer leaving the operation system written on the disk in original condition.
In the later chaotic development of proDOS by Apple and due to the fact, that Apple didn't even try to keep a kind of compatibility or
standard within proDOS and changed memory adresses of the driveparameters within months of kicking off new versions of ProDOS
out to the customers, it finally turned out to become nonefficient to this revolutionary kind of drivecontroller to release every few months
a new release of eprom to keep track with the chaotic policy of Apple and it's rapic changes within it's different kinds of proDOS versions.
Therefor the last final release of the eprom of this controller was only able to support ProDOS up to the Version of ProDOS 1.1.1.
But this controller supports also still all versions of UCSD Pascal, CPM 2.2 in 44k and 56 k version as well as DOS 3.2 and DOS 3.3.
It would become cowadays a usefull task after the rush of all that different versions of ProDOS finally ended up with the ProDOS
version of 2.0.3 / 2.0.4 and the final release of the OS of System 6.01 at the IIGS to now modify the epromcontents to support that final
versions of the last released operation systems and then get this revolutionary controller updated to nowadays needs. The last valid version
of the eprom is numbered as 9.1.
This would enable the users to use the now availiable operations systems without juggeling around with numerous amount of differents kinds
patched disk versions depending to the current used configuration and turn back to the freedom of configuring the drives with the currently
required configuration and just setting up the switchblock to the current configuration and allways just using the unpatched and original
version of each operation system.
You may use any kind of mixing of drives within the 2 conected drives. So you might for example use in one case the 35 track DISK II as
startupdrive and a doublesided 80 track drive as secondary drive with the option of bundeling that 2 x 80 tracks to one disk with 160 tracks!
And with next startup you may easily change the order of the drives without patching any disks just by changing the switches in the
driveconfiguration switchblocks. The process of patching the driveparameters only in memory is referred in the manual by the term:
"autopatch" by automatic RAM patching in memory.
I do have the source codes of the eprom as printed listing somewhere within the hige amount of dosumentation in my archives....
so with further progress of digitallizing my archives i will add that listing sometime in future when i stumle across that listing and
when i have scanned it.
Up till now i will show below the parts of documentation that is availiable yet.... ( circuitplan and manual in german language )
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and german court decision:
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