Detecting inserted floppy drive WAS: Raymond Check discusses MS DOS Floppy Disk Cache

Chuck Guzis cclist at
Wed Oct 2 18:45:13 CDT 2019

On 10/2/19 3:15 PM, Fred Cisin via cctalk wrote:
> Sorry, I was assuming the previous discussion!
> This implies that some newer drives actually had a "disk present"
> signal, or wouldn't let you close the door without a disk, but had a
> door signal.
> Rather than an "unnecessary" training insertion, couldn't the testing of
> drive type have simply waited until first actual use?
> (a 5.25 would have shown write-protect while the disk was half in.)
> Whether or not a drive had "DRIVE-READY" was not reliable enough, unless
> you deprecated use of old drives, . . .

Regardless, the Win95 solution to identifying disk changes was to
attempt to rewrite the volume system ID and serial number in the boot
sector on every inserted disk that was write enabled.  If that screwed
up the usability of the disk, well, tough luck.

They called it "volume tracking".  You can identify such modified disks
as having the "xxxxxIHC" as the system ID, where "xxxxx" was some random


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