---

The following is an exerpt from a text file written/complied by one A.D. Longton of Rockville, MD. I have omitted the discussion of how to make a 1.44M disk from a 720K disk with a soldering iron since I don't want to be a party to furthering that practice. I did, however, find the remainder of the information quite interesting and have included it here. As You can see, it comes directly from the 'brain trust' at Big Blue and may tend to lend some measure of credibility to what I've been saying all along. The original file was dated 5/10/89, I'm not sure when the information spewed forth from Boca Raton. -[Steve]- (tm) ------------------------------------------------------------------------------- 3.5" DISKETTE FORMATS Kevin Maier IBM Corporation Boca Raton, Florida "Reprinted by permission of the IBM Personal Systems Technical Journal." Page 42, issue 2, 1989 "The original recommendations about the proper formatting and use of PS/2 diskettes have undergone revision. This article explains why the recommendations have changed. THE ORIGINAL CAUTION Personal System/2 shipping cartons include a sheet of paper that cautions users not to format a 2.0 MB diskette to 720 KB, because the diskette becomes unusable and should be discarded. This caution was issued because of the physical properties of 720 KB diskettes versus 1.44 MB diskettes. The 720 KB format uses a higher write current, and the 1.44 MB format uses a lower write current. To accommodate the higher write current, the oxide coating on a 1.0 MB (720 KB formatted) diskette is denser than the oxide coating on a 2.0 MB (1.44 MB formatted) diskette. When you format a 2.0 MB diskette to 720 KB, you apply the higher write current to the less dense oxide coating. The hardware developers originally felt that this meant the 720 KB formatting pattern is written too deeply into the 2.0 MB oxide coating, causing intermittent data errors and unreliable use. Furthermore, the developers felt that if you attempted to reformat the diskette to 1.44 MB, which uses the lower write current, the 1.44 MB format would not completely write over the "deeper" 720 KB format. Therefore the developers' recommendation was to discard a 2.0 MB diskette that was formatted to 720 KB. THE SUBSEQUENT FINDINGS [aka a RETRACTION] Since the time that this caution was issued, the developers have performed additional testing, and have concluded that there is no need to discard a 2.0 MB diskette that was formatted to 720 KB. It is still true that a 2.0 MB diskette formated to 720 KB will cause intermittent data errors. However, the latest assessment is that you will be able to reformat the diskette to 1.44 MB and use it reliably after that. The same logic applies to a 1.0 MB diskette formatted to 1.44 MB. You cannot use it with the 1.44 MB format, but you can reformat it to 720 KB and use it reliably after that. Therefore, the current recommendation is: If you format a diskettte to the wrong capacity, do not discard it; instead, reformat it correctly and use it." With all those feelings and recomendations on those feelings it makes me wonder how much experimentation was actually being done on a strictly scientific level. Note that the one mention of formatting 1.0mb disks to 1.44 MB does not say that you will get errors if you use them. What it does say is that if you reformat that wrongly formatted disk, you can reliably use it at 720 KB. The implication is that since there were errors with 2.0mb disks formatted to 720 KB "logic applies" that there will be errors if the reverse is done. This is not necessarly the case, and we are not told why, we are just told. FYI, here are the specifications for the 720 KB, 1.44 MB, and 360k 5.25" disk drives as listed in the same issue on pages 43-44. Note the large similarity between 360k and 720 KB disks and 720 KB disks and 1.44 MB disks. 720 KB and 1.44 MB Diskette Drives 720 KB 1.44 MB 360 KB (5.25") Access time: Track-to-track 6 ms 6 ms 6 ms Head settle time 15 ms 15 ms 15 ms Motor start time 500 ms 500 ms 750 ms^ Disk rotational speed: 300 rpm 300 rpm 300 rpm Maximum Latency 200 ms 200 ms 200 ms Formatted Characteristics: 720 KB 1.44 MB^ 360 KB^ Tracks (actual) 80 80 40 ^ Tracks per inch 135 tpi 135 tpi 48 ^ Sectors per track 9 18 ^ 9 Bytes per sector 512 512 512 Bytes per track 4608 9216 ^ 4608 Data heads 2 2 2 Sector interleave factor 1:1 1:1 1:1 Sector skew factor 0 0 0 Sectors per cluster 2 1 ^ 2 Transfer rate 250,000 500,000^ 250,000 (bits per second) (All ^'ed numbers are numbers that are different from the 720 KB format.) "...if they think you're technical, go crude. .... These days, though, you have to be pretty technical before you can even aspire to crudeness." --From William Gibson's short story Johnny Mnemonic

---

The views and opinions stated within this web page are those of the author or authors which wrote them and may not reflect the views and opinions of the ISP or account user which hosts the web page. The opinions may or may not be those of the Chairman of The Skeptic Tank.

Return to The Skeptic Tank's main Index page.

E-Mail Fredric L. Rice / The Skeptic Tank