MS-DOS 5.0 and IBM AT with BIOS dated 1/10/84 (75787)

The information in this article applies to:
    Microsoft MS-DOS operating system 5.0
    Microsoft MS-DOS operating system 5.0a

This article was previously published under Q75787


When Microsoft MS-DOS version 5.0 is installed on an IBM AT with a BIOS dated 1/10/84, disk access may be noticeably slower. Increasing the disk interleave should solve this problem.


A third-party utility, such as Spinrite or Norton Utilities, can be used to modify a disk's interleave. Increasing the disk's interleave by one should solve the problem. For example; if the interleave is 2:1, change it to 3:1.

Disk interleave is:

"the physical arrangement of data sectors on a disk in such a way that sequentially read sectors are not necessarily contiguous. A disk, especially a hard disk, usually spins so fast that the computer cannot process the data from one sector before the next sector passes the head. Interleaving alternates sectors in a pattern that increases the likelihood that when the computer is ready for the next sector in numeric sequence, it will be the sequence just arriving at the head."

This definition was obtained from "Computer Dictionary," published by Microsoft Press.

More information on disk interleave can be found in "The MS-DOS Encyclopedia" or "Advanced MS-DOS Programming," which is published by Microsoft Press.

The products included here, Spinrite and Norton Utilities, are manufactured by vendors independent of Microsoft; we make no warranty, implied or otherwise, regarding this product's performance or reliability.

Modification Type: Major Last Reviewed: 9/30/2003
Keywords: KB75787