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From: TLC (all posts)
Date: 1998-07-02
Subject: Re: Turbo emulating

Hi!

> When I converted 9 sec. formatting from Plus/4 to the Amiga a
> year ago (it was an easy job), somebody asked me to write a turbo
> communicating interface for the Amiga. (Between non modified 1541
> and Amiga of course.) Because there is none.
> I tried, and I failed. I tried to convert Pigmy's turbo loading-
> saving from Bard's Tale III. (It is really nice! Even can
> formatting!) But there was some instruction timing, and I lost my
> hope, I was unable to get the real timing for the instructions, and
> emulate it on the Amiga side.

I have no idea on the 68K. But I do have it on the communication.

What would happen, if you avoided asynchron communication, and you used synchronised data flow instead?

Since ATN can't be written by the drive, it would make sense to use CLK and DATA as datalines, and make them synchronised by alternating between 0's and 1's on the ATN line from the Amiga. The synchronising signal would be timed using the CIA in the Amiga, or whatever regular timing method (all you should provide, that the timing may not be faster than actually, the 1541 is able to fresh the datalines). The program in the drive would put the datas to the two lines exactly as early, but it would synchronize this to the rise and fall of the ATN input. Of course, you have to be sure somehow that the datablock is present in the memory of the drive, before starting the transfer.

Maybe, this would mean a small loss of the speed, in opposition of a programmed, cycle timed data-transfer, but it would work much more reliably (...at least, 'cos you can't present exact timing for all Amiga versions with all processor and memory types, not to mention the multitasking kernel of the Amiga OS).

Levente

Ps. How about contacting Joe Forster (...Kovacs Balazs), author of Star Commander, 1541 handler for DOS? ...He may have had these problems too,
when programming his Commander. BTW, I'm sure you'll meet him at Scenest.