Firewire 4pin-4pin for My Book Premium

My Laptop has a 4-pin firewire connector. The firewire cable that came with MyBook is the 6-pin to 6-pin. Can I use a 6-pin to 4-pin cable to connect my laptop to the My Book Harddrive?

I don’t want to use USB!

Yes, it works with 1394b (6pin) & 1394a (4pin), but 4pin/1394a is slower than 6pin/1394b.