Origin of "partition" in storage devices

Fred Cisin cisin at xenosoft.com
Mon Jan 31 17:19:35 CST 2022

>> On Mon, 31 Jan 2022, Grant Taylor via cctalk wrote:
>>> I think the same type of problem happened with the really old FAT-12 to 
>>> FAT-16 conversion.
>>> Wasn't FAT-12 limited to something near 31 MB?

> On Mon, 31 Jan 2022, Fred Cisin via cctalk wrote:
>> 32 MebiBytes - 1

On Mon, 31 Jan 2022, geneb wrote:
> *chases Fred out of the house with a broom, screaming incoherently about SI 
> units*

Sorry that I was in the house with a broom, screaming incoherently about 
SI units.

I think that the correct number is 33,554,432 bytes

File sizes were stored as the last 4 bytes of each DIRectory entry, with a 
signed 32 bit number. So, a file could be from
-2,147,483,648 to 2,147,483,647
Unfortunately, they never successfully finished the implementation, 
so copying a negative size file to the drive did not increase the free 
space.  Since they didn't make THAT work, perhaps they should have used an 
UNSIGNED 32 bit number, to permit files up to 4,294,967,295

The 5160/XT original drive was 306 cylinders, with 4 heads, and 17 sectors 
per track for 10,653,696
for 10.653696  "MegaBytes" 1,000,000 10^6
or 10.404      Marketing "MegaBytes" 1,024,000    10^3 * 2^10
or 10.16015625 MebiBytes  2^20

Seagate, and a few others, were smart enough to call that 10MB, so that 
people forgave them a few bad tracks, and even bragged how great the drive 
was because it was even more than the ad had called it!

Grumpy Ol' Fred     		cisin at xenosoft.com

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