partition sizes in 4BSD systems

[Joseph S. D. Yao]

In article <317 at l5.uucp> gnu at l5.uucp (John Gilmore) writes:
>In article <100 at hadron.UUCP>, jsdy at hadron.UUCP (Joseph S. D. Yao) writes:
>> For BSD, the root partition is always 15884 sectors ... This is nice
>> and reasonable for an RP0[456].  ...  Partition B, often used
>> as swap, is 33440 sectors long.
>Hmm, I always wondered where those numbers came from.  ...

>From /etc/disktab:
rp06|RP06|DEC RP06:\
	:ty=removable:ns#22:nt#19:nc#815:\
	:pa#15884:ba#8192:fa#1024:\
	:pb#33440:pc#340670:\
	...
	:ph#291346:bh#4096:fh#1024: (actually, no longer true)
				    (because they drop 3 tracks)
				    (for bad block information.)
19 sectors/track, 418 sectors/cylinder.
 38 * 418 = 15884
 80 * 418 = 33440
697 * 418 = 291346
===
815

Oddly enough,

rm03|RM03|DEC RM03:\
	:ty=removable:ns#32:nt#5:nc#823:\
	:pa#15884:ba#8192:fa#1024:\
	:pb#33440:pc#131680:\
32 sectors/track, 160 sectors/cylinder.
 209 * 160 = 33440

rm05|RM05|DEC RM05:\
	:ty=removable:ns#32:nt#19:nc#823:\
	:pa#15884:ba#8192:fa#1024:\
	:pb#33440:pc#500384:\
32 sectors/track, 608 sectors/cylinder.
 55 * 608 = 33440

But nothing else fits.	;-)
-- 

	Joe Yao		hadron!jsdy at seismo.{CSS.GOV,ARPA,UUCP}