U
uraniumore235
why does a 329K floppy disk with 1K block size need a 12-bit block
number?...please help with this historic HDD question.
number?...please help with this historic HDD question.
A
Alexander Grigoriev
FAT12 was used before FAT16. It only allows up to 4095 clusters (which
usually are sector-sized). Floppies allow to use that.
I don't quite understand why it's a question. It doesn't "need", it just can
use it.
usually are sector-sized). Floppies allow to use that.
I don't quite understand why it's a question. It doesn't "need", it just can
use it.
A
Arno Wagner
Previously Alexander Grigoriev said:
I think the answer lies in what the next smaller number would
have been. Probably 8 bit, which is too small for most floppies.
Arno
R
Rod Speed
It doesnt, but clearly FAT12 was what was considered to be adequate
initially for both hard drives and floppys and wasnt adequate for very long.
A
Alexander Grigoriev
Well, there never were FAT8.
Of course, 329 sectors would fit to 9 bits block number, but it would not
make sense to produce too many different FAT variants.
Of course, 329 sectors would fit to 9 bits block number, but it would not
make sense to produce too many different FAT variants.
A
Arno Wagner
Previously Alexander Grigoriev said:
I know. I just think that was the next-smaller step.
In these days, bit-shifting was expensive. The barrel-shifter
(rotates/shifts in 1 clock tick) was only introduced in the 486, if
I remember correctly.
Arno
A
Arno Wagner
.... and FAT12 only needs a nibble-flip, which I think was a low-cost
op in the older CPUs or can be done with a small table....
Arno
A
Ardent
X-No-Archive: yes
Like Bill's great words of yore "Who needs more than 64 kb"
)
Like Bill's great words of yore "Who needs more than 64 kb"
)
R
Rod Speed
Like Bill's great words of yore "Who needs more than 64 kb"
Yeah, its taken the industry a long time to grasp the basics of Moore's Law etc.