how to use --checksum-seed ?

[CSights]

Hi,
	I've been trying to use "--checksum-seed" to speed up backups .  I have a 
homebrew script which creates incremental backups using hardlinks.  To save 
disk space I turn on --checksum so that when file's mod-times change rsync 
doesn't create a new file (breaking the hardlinking) unless the contents of 
the file are different as well.
	I tested the command:

#rsync -aHiy -r --delete --ignore-errors --checksum --checksum-seed=1 fromdir 
todir

	but I couldn't find where the checksums were being cached.  

	How does one use --checksum-seed ?

Thanks!
	C.