Skewed +3 Disk Format

"FORNOMINAL FORMATTER"


SKEWED +3 DISK FORMAT


by Barry McConnell





Guess where I'm going on holiday this year. No, Ireland actually. And


guess where this month's first program comes from. Wrong, it's Ireland


again. Spooky or what? I hope it'll be nice and sunny over there,


though. From what I've heard it tends to be a bit damp, and I'd hate


to have to spend the whole time stranded in a pub brooding over a pint


of Murphys. Although actually ...





Barry McConnell gets a pat on the head for this one (or should that be


a Pat?). He's noticed that the standard +3 disk formatting routine is


a bit crap, and he's come up with an alternative which'll speed things


up by up to 60% (40% on average) just by formatting the disk in a


different way. The way it works is rather technical, so skip the next


paragraph if you're not bothered about the details (and go away


altogether if you haven't got a +3).





"Skewing" is what it's all about. (No - "skewing".) When the +3


normally formats a disk it numbers the sectors of each track in order


from one to nine. While this might seem reasonable enough, as that's


the order they're read in, in practice you tend to find that when the


drive has finished reading one sector, the next has whizzed straight


past and has to wait for another revolution of the disk for it to come


round again. Hassleville, Arizona. The solution is to number the


sectors differently while the disk is being formatted. How about one,


eight, six, four, two, nine, seven, five, three? This means that each


sector should slide neatly into place just when it's needed.





Getting the program working is so easy you could probably do it with


your eyes shut. Just type in the hex dump (using the Hex Loader) and


save it. Then CLEAR 47999, LOAD "" CODE and there you have it. To


start formatting just slot in the disk that needs doing and PRINT USR


48000. And off it goes. Make sure you've put the right disk in and


everything, as there's no warning before it kicks off. The number


returned by the PRINT statement will be 0 if everything went okay, and


the appropriate DOS error number if there was a prob.





Enjoy.