Search found 120 matches

by TeaRex
Thu Jan 06, 2011 10:37 pm
Forum: Support
Topic: Track 0 disable signal on pin 33 - how to trigger?
Replies: 8
Views: 3163

Re: Track 0 disable signal on pin 33 - how to trigger?

Bummer. I just spent most of the day fixing this drive, and now it works as well as it's supposed to... but won't be useful for dumping. Well, thanks for the info. Just to bug you with YET ANOTHER question: Do you maybe know if there are any manufacturer whose drives tend to be able to do -8 after m...
by TeaRex
Thu Jan 06, 2011 10:00 pm
Forum: Support
Topic: Please explain what DTC does on giving up
Replies: 5
Views: 1612

Re: Please explain what DTC does on giving up

Yes, it's more clear now. Thanks a lot to both of you! I'll see what I can do with those old disks.
by TeaRex
Thu Jan 06, 2011 9:38 pm
Forum: Support
Topic: Track 0 disable signal on pin 33 - how to trigger?
Replies: 8
Views: 3163

Track 0 disable signal on pin 33 - how to trigger?

Mechanically my 5.25" drive (label says Newtronics D509V2..., motor is by Mitsumi) should be able to go a bit below track 0. I'd guess it does -4, probably I can make it reach -8 (slightly more than 2 mm below track 0, right?) with a bit of filing. Reading tracks 8 and above on the back side of flip...
by TeaRex
Thu Jan 06, 2011 12:07 pm
Forum: Support
Topic: Please explain what DTC does on giving up
Replies: 5
Views: 1612

Re: Please explain what DTC does on giving up

So do I get this right, even if only 1 sector of 18 was bad and 17 were perfectly readable, DTC writes that whole track in the sector image as empty, or not at all? If so, I'll wait for the documentation of the stream format. It looks like by and large, every byte encodes the length of one flux reve...
by TeaRex
Wed Jan 05, 2011 6:17 pm
Forum: Support
Topic: Please explain what DTC does on giving up
Replies: 5
Views: 1612

Please explain what DTC does on giving up

If DTC gives up on a track with errors in it after the maximum number of retries is reached - what is stored then in the (non-stream) image? The last read attempt? The single best read attempt? Or a collective "best of" that takes good (or nearly good) sectors from different reads and puts them toge...
by TeaRex
Fri Dec 10, 2010 5:30 pm
Forum: Support
Topic: Negative track numbers
Replies: 14
Views: 3758

Re: Negative track numbers

Sure but what's the point? If a publisher did this, it wouldn't offer protection against anything more complicated than DISKCOPY.COM and the fact that you'd have to flip the disk would 1.) inconvenience the legitimate user and 2.) give away the trick to anybody even remotely tech savy.
by TeaRex
Mon Dec 06, 2010 9:56 pm
Forum: Support
Topic: Apple ][ disks
Replies: 12
Views: 7639

Re: Apple ][ disks

Even the Apple drives can usually read data fine if you're just a quarter-track away from the "right" position, thanks to the width of the head; valid data has to be at least one full track away from any other valid data to be readable. Thus, quarter tracks weren't useful for protection purposes on ...
by TeaRex
Wed Dec 01, 2010 2:00 am
Forum: Support
Topic: Apple ][ disks
Replies: 12
Views: 7639

Re: Apple ][ disks

OK, I'm breaking my promise and continuing my rants... In the Apple controller the "MSB is always 1" rule is also used to delay the next bit-shifting by up to 3 cycles during reading, so that the fastest possible 6502 loop construct for checking whether a byte is complete (LDA abs,x + BPL, which tak...
by TeaRex
Tue Nov 30, 2010 6:20 pm
Forum: Support
Topic: Apple ][ disks
Replies: 12
Views: 7639

Re: Apple ][ disks

Yeah, I was more or less answering to the post by mr.vince above, but without carefully reading it in the first place. Obviously you must understand the formats before they can be supported. And since the disk read routines in the Apple can in fact use much more RAM than in the Commodore drives whic...
by TeaRex
Tue Nov 30, 2010 6:20 am
Forum: Support
Topic: Apple ][ disks
Replies: 12
Views: 7639

Re: Apple ][ disks

Just FYI... Apple II drives are not intelligent at all, they use a low-level bitstream transfer from/to the host computer. The early and widespread "Disk ][" drive contains only four small ICs. There is one exception, the "Unidisk 3.5", which IS an intelligent drive containing a 6502 CPU that is fas...