Donald Duck wrote on Today, 19:10:

So you are saying that when he was refering to 2 X heads he ment both sides of the disk

Yes, I believe so - each of the two head read/writes one of the two sides of the disk.

DaveDDS wrote on Today, 19:17:

Donald Duck wrote on Today, 19:03:

... But this is single sided, 720mb right?

The PC never used single-sided disks. The main difference is DD (Double Density) .vs. HD (High Density)

The original XT had 5.25" DD drives - 40x2x9x512 = 360k

But where is the X2 comming from? because it was single sided right?

Donald Duck wrote on Today, 20:02:

DaveDDS wrote on Today, 19:17:

The original XT had 5.25" DD drives - 40x2x9x512 = 360k

But where is the X2 comming from? because it was single sided right?

I don't believe the PC ever officially used single-sided drives - the x2 is two heads (40 tracks, 2 heads, 9 sectors/track, 512 bytes/sector)

I think the XT might have used 8 sectors/track at first = 320k

The original XTs did use full-height drives - twice as tall as "modern" drives - this was also the form-factor of the first drive (SA-400) which was single-sided - perhaps this is confusing to some.
But double-sided full-height drives did exist (and were used in the XT) and there were even a few half-height single-sided drives along the way (which I never saw in a PC, but were used on some other systems)

To see what various drives physically look like, check out this pic:

http://dunfield.classiccmp.org/misc/h/floppy.jpg

Thas has:
8" full height
8" half height
5.25" full height
5.25" half height
3.5" desktop
3.5" laptop

DaveDDS wrote on 58 minutes ago:

Donald Duck wrote on Today, 20:02:

DaveDDS wrote on Today, 19:17:

The original XT had 5.25" DD drives - 40x2x9x512 = 360k

But where is the X2 comming from? because it was single sided right?

I don't believe the PC ever officially used single-sided drives - the x2 is two heads (40 tracks, 2 heads, 9 sectors/track, 512 bytes/sector)

DaveDDS wrote on Yesterday, 02:08:

> FORMAT A: /T:80 /N:9

Donald Duck wrote on 2026-09-26, 19:00:

I have a batch of 3.5" Atari disk (DS and DD).

So the 3.5” disks that I formatted are double sided and double density And are of 9 sectors each on 80 tracks on each side (512 bytes x9x80x2=737.280 MB)

So if I want to format a 3.5” double sided and double density which is 1.44mb which is double the original? is it double the the amount of sectors per track or double the total of tracks?