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• All names with a copyright are acknowledged.
• If the reader uses information from this document to write software or build hardware, then it is on his own account. I cannot be held responsible for blowing up your computer, mother-in-law or whatever; it will always be your own fault.
• I'm not a sexist, with 'he' and 'him' I also mean 'she' and 'her'.

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What is it
The IDE-harddisk has 16 datalines and 7 controllines. The two ports used for the keyboard can handle the data and the userport can serve the controllines.

The big advantage of the above proposal is that there is relatively less soldering to do then when building a real IDE-interface. But you need to replace the Kernal and you need an additional powersupply for the HD itself.
The disadvantage is that it will be completely incompatible to any existing system. So any software circumventing the Kernal for loading/saving data won't see the IDE-HD.
What ever other disadvantages you can think of, don't forget the two big advantages:
* the huge amount of data you can store on the harddisk ( and maybe CD-ROM)
* the huge speed with which you can load/save data comparing to an original 1541

Results
I have build it and it works. That is, I proved that I can turn the motor of the harddisk on and off again. Doesn't sound great but it proofs in a simple way that the interface works. Now I only have to find someone who is willing to write a Kernal for it.

The Kernal
Whatever system we choose, we'll need a filesystem and software to handle it. I doubt that it fits all in the original Kernal. One idea is to replace the BASIC-ROM with a bigger one and to use one output of the USERPORT for selecting the part of the ROM to be used.

The future..
Unfortunately there is no future for this design. There already exists IDE64 and I don't feel the need to compete with these guys.
Another problem is its 1541 compatibility: quite some programs expect to find a real 1541 as device eight and want to address it directly, simply disregarding the Kernal. And in this case there isn't one found. Result: no running program!