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PC Q&A
by Jim Sanders - November 03, 2001 at 18:45:40:
PC Q&A SIG by Jim Sanders, NOCCCI promised that I would try and get one of the new Que! Super Disk FD32MB 240MB products for show and tell at the October SIG, and I was able to do that. In the process I was able to answer the question that had been bugging me for almost a year. "How do they get 32 Megabytes of data on a standard 2 Megabyte piece of media ( aka 1.44M FD ). For those of you that know what that means, skip the following explanation. The standard 3.5 inch media that we buy will actually hold 2 Megabytes of data. The ways in which we format the diskette changes the usable capacity. The MS_DOS standard of 80 tracks on each side with 18 sectors per track and 512 bytes per sector, gives us the 1.44M that we are used to hearing. 80 (tracks) x 18 (sectors) x 512 (bytes) x 2 (sides) = 1,474,560. Wait a minute, that is not 1.44M. Which is true. But we say 1K, and think 1000 decimal, when we really should keep in mind that we are talking computerese and referring to a binary numbering system number. The binary number of 1111111111 (1024 in decimal) is the base 2 to the tenth power. Just like we are rounding off the binary 1024, to the decimal 1000, lets try it by rounding of the binary 111111111 (512 in decimal), to the decimal 500. 80 (tracks) x 18 (sectors) x 500 (bytes) x 2 (sides) = 1,440,000. TAH DAH. The house keeping overhead of numbering all those sectors, of providing a gap between them, etc., uses up a lot of the maximum potential capacity. A more efficient layout, like the MS "file.CAB" format, gets 1.7M per diskette. The drive has 2 read/write heads per side. One for the 80 track 720K/1.44M media, and one for the 2490 track LS120M/LS240M media. That is 31 tracks in the high capacity mode in the same space as one track in the standard floppy mode. Because they can move the head in much finer steps than a regular floppy, they can perform a clever trick when writing in the 32MB mode. They first write track zero in the regular format that is readable by standard 1.44 drive. When track zero is read by a standard 1.44 drive, it will show a "FD32MB.SYS and README.TXT" file. The README.TXT file will explain that this media is formatted as 32MB. Then they write track one and then offset the head a small part of a track and write again. This erases and over writes most of the first track but leaves a skinny slice of the first track untouched. Now that the second track is written, they then offset the head a small part of a track and write the third track. This erases and over writes most of the second track but leaves a skinny slice of the second track untouched that is next to the skinny piece of the first track. This process is repeated until all tracks are written. This takes about 8 minutes for 32MB. Reading the same data from the 32MB floppy and writing it to the hard disk, took 1.5 minutes. This makes the 32MB mode an erasable WORM (Write Once Read Mostly) drive. In the more current vernacular, like writing a CD using a piece of CD_RW media in the standard CD mode instead of the packet writing mode. That is to say that it is very much like burning a CD_R. However much data you want to put on the media, up to 32MB, you must compile it into a list first and have a special program write it to the media. Once that is done, you can random access read any of the files that are on the diskette. Again, just like a CD_R. Only, just like a CD_RW, it can be erased and reused. To put it another way, if you want to erase a file, change a file, or add a file, you would have to erase the entire diskette and repeat the process that created it to begin with using the special write program. Of course only one of these Super Disk drives can read other than track zero on a "1.44M" floppy that has been formatted in the 32MB mode. So much for my dream of a true 32MB floppy!
On the plus side, it reads standard diskettes much faster than a regular floppy drive, it does both the 120M and 240M high capacity formats. It is a small self_contained package that includes a permanently attached 5" USB cable that stows in a slot on the side of the drive. It is powered by the USB bus and does not require any additional power hook_ups. Playing sneaker net with this drive is a pleasure. Hot plug it into one machine, copy the data you want (up to 240M), unplug it, hot plug it into the second machine, and copy your data. This drive makes a nice addition to the Panasonic digital camera that I own, which uses the LS120 diskettes to record up to 50 hi_res pictures.
Next month I will try to have installed Windows XP on a machine, and touch on my experiences with Windows XP and what I think of it.
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