Even the DDR2 can be surprising.
I have 2x2GB DDR2-667 Kingston Valueram, currently running 867Mhz
http://www.hwbot.org/community/submission/2151928_dublin_gunner_wprime_1024m_phenom_x4_9550_7min_16sec_531ms
http://valid.canardpc.com/show_oc.php?id=1753748