John, Assuming you are puzzling over the supposed model numbers, applying some wild and unfounded speculation, we may suppose that "27" was selected for the 2nd and 3rd numbers in the number of cylinders number - now I have to say "Why they chose this algorithm I do not know.". One may now suppose that the "54" was just double "27".
Regarding the 7 and 15 discrepancy in the number of cylinders, I vaguely remember that disk technology involved keeping a number of spare tracks in reserve - maybe still do - and perhaps there are 7 cylinders worth of spare tracks in the case of the "-27" and 15 cylinders worth of spare tracks in the case of the "-54". Chris Mason ----- Original Message ----- From: "John P Kalinich" <[EMAIL PROTECTED]> Newsgroups: bit.listserv.ibm-main To: <[email protected]> Sent: Friday, 09 December, 2005 5:16 PM Subject: Re: 3390-81 > >Kees said... > > >The 3390-27 and 3390-54 models still serve a functional purpose: -27 has > 32767 cylinders >= halfword minus topbit, the -54 has 65535 cylinders = > halfword. > >When the halfword boundary will be / has been lifted, there is no reason > to define a >new boundary a three times the -27. If any it will be skyhigh, > like a 32bits or 64bits >value. > > > I thought the -27 had 32760 cyls and the -54 had 65520 cyls. Why they > chose these values I do not know. > > Regards, > John Kalinich > Computer Sciences Corp > > ---------------------------------------------------------------------- > For IBM-MAIN subscribe / signoff / archive access instructions, > send email to [EMAIL PROTECTED] with the message: GET IBM-MAIN INFO > Search the archives at http://bama.ua.edu/archives/ibm-main.html > ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to [EMAIL PROTECTED] with the message: GET IBM-MAIN INFO Search the archives at http://bama.ua.edu/archives/ibm-main.html
