'W.A.R. (Martech 1986)'
Author:Pete Rittwage (registered user: 558 posts )
Date: Tue, Jan 31st, 2012 @ 09:27 ( . )

On 01/31/2012 @ 00:37, hyper active wrote :
the expected values are 0D 0B 09 01 02 02
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'09 01 02 02' is illegal GCR and will give back random values on a real 1541. It can't "expect" that sequence because it will never get it.


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'W.A.R. (Martech 1986)'
Author:Lord Crass (guest: search)
Date: Thu, Feb 02nd, 2012 @ 22:23 ( . )

It's not looking for GCR values. The track sync protection just records into the drive memory what sector it lands on when it moves from one track to the other. You wind up with a table in drive memory ($0568) of 6 sector numbers: 13, 12, 9, 1, 2, 2.

The C64 retrieves these values and either compares them to hard-coded values, or uses them in a transform or key of some sort. I never got around to finishing off the analysis of the compiled basic, so I'm not entirely sure what it does with them.


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'W.A.R. (Martech 1986)'
Author:hyper active (registered user: 296 posts )
Date: Sat, Feb 04th, 2012 @ 02:52 ( . )

I've been trying to write back the tracks in question from the g64, but I'm not getting anywhere. Is there a special switch in nibwrite that I need to use? I've had a look at each track, and the sector header info is all messed up.
For example, normal tracks start with a few sync marks and then 0x52, but track 29 starts with 4a 52 94 a5 29 and so on. and then there is a 04 at the end.
How do I write these out properly?


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'W.A.R. (Martech 1986)'
Author:hyper active (registered user: 296 posts )
Date: Sat, Feb 04th, 2012 @ 14:55 ( . )

Oh. My. God. I got it working!
Following a hunch, I
Extracted the entire g64 into a bunch of raw tracks, then wrote back tracks 28-35 with the -b? -t switches.


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'W.A.R. (Martech 1986)'
Author:hyper active (registered user: 296 posts )
Date: Tue, Feb 07th, 2012 @ 20:14 ( . )

Update: this doesn't seem doable with a zoom floppy, only the lpt port interface. The zoom interface seems to want to align the tracks too far apart.... which presents a problem. I need to upgrade my machine. Do mobo manufacturers still make boards with onboard lpt ports? if not, we could be in serious trouble.


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'W.A.R. (Martech 1986)'
Author:Nate (guest: search)
Date: Wed, Feb 08th, 2012 @ 02:28 ( . )

ZF could handle this, code would just have to be written to compensate for the delay. Or use a 1571 or 1541 with IHS.


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'W.A.R. (Martech 1986)'
Author:hyper active (registered user: 296 posts )
Date: Wed, Feb 08th, 2012 @ 14:10 ( . )

Oops, looks like I'm out of luck then, I don't know of anyone Here in Melbourne who could equip my 1541 drive with an IHS.... and I'm certainly not going to attempt it myself.


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