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Ever wondered why Windows FAT32 volumes are limited to 32GB?

Handheld PC News

Posted 3 weeks ago | News | Chris Tilley 1 comment

If you have been on HPC:Factor for long enough, you will be well aware that for Windows CE 2.11 and higher devices there is a limit of 32GB for FAT32 volumes on CF cards. This limit does not apply to older CE 1.0 and CE 2.0 devices, which can only make use of FAT16 and in-turn are limited to 2GB partition sizes. You may also know that these same limits apply to DOS and older version of Windows, including Windows 95, 98 and even XP. But do you know why the limit exists?

In an interesting twitter post post by former Microsoft developer Dave Plummer, he outlines precisely why the limitation exists: that one Thursday morning some 30 years ago, he simply picked a number!

While quickly designing the format dialogue for Windows NT, he alleges that he arbitrarily picked a cluster size that, arriving at 32GB as its maximum volume size, must have seemed back in 1994 as almost infinite. In practice, the decision would constrain Windows' support for FAT32 partitions at 32GB instead of the maximum possible size of 2TB that would be possible using a 512 bye cluster size. This is presumably because as Microsoft already had drives out in the wild operating on that cluster size, it became difficult to communicate and in turn switch the cluster size to something else later on.

You can read the full post on the creation of the Windows NT format dialogue at the link below, however I note a slight anomaly with the story. Windows NT, be it version 3.1, 3.5, 3.51 or 4.0 had no native support at all for FAT32. This creates a bit of a question over why consideration was being given for it at all in the 1992-1995 time period that marked the NT 3 era. In fact, at the time, the original release of Windows 95 didn't have any support for FAT32 either, with it only arriving as part of Windows 95 OEM Service Release 2.1 (4.03.1212-1214 [4.00.950B]) in August 1997.

Perhaps Microsoft were intending to support FAT32 under Windows NT after all? Instead, it wouldn't be until the release of Windows 2000 that true, native support arrived on the platform.

View: Dave W Plummer on Twitter (X)
Posted on 25 March 2024 at 14:26By Chris Tilley (C:Amie)

Comments on this article

fantablium's Avatar fantablium 29 March 2024 10:27:15 AM
I did wonder how the maximum cluster size had been determined and like so many things someone just made it up!
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