The rx4640 is interesting as it makes use of so-called "cell"-architecture, unlike the single- "cell" "entry-level" systems (like the rx1600/rx1620, zx6000/rx2600/rx2620 and so forth), thus a bit more like the 'big iron' Integrity systems (like the rx7620, rx8620 and the Superdome). I believe the rx4640 can take two, which can be fitted with four single-core processors each or two "mx2" dual-processor modules (as seen in the first Integrity Superdome systems). It certainly matters not; however, I believe myself to be correct in stating that cell architecture begins at the rx76 level and above.The non-cell rx6600, for example, is considered "entry level", is fashioned for the [mostly non-existent] HP/UX app-tier space due to the large number of onboard SAS drives (I have eight... I believe it will hold 16). Otherwise, a large number of onboard drives, as you've alluded, is pointless since HP/UX finds itself mostly within the database tier (rx7640, etc.. hold four onboard u320s). Boot from SAN with HP/UX is, again, rare (said "pointless"), since the complication that ensues has little (if any) return on investment excepting, perhaps, infrastructure based disaster recovery. The rx4640 should hold four dual-core I2s (1.6GHz / 24MB L3), and should have Madison / Tukwila availability to allow one to run openVMS under HP Integrity Virtual Machines.