Bridge Chipsets in Plextor Enclosures?

What bridge chipsets does Plextor use for their square PX-740UF, PX-750UF, and PX-755UF enclosures? I’m talking about the enclosure chipsets, as in Firewire and USB2.

Are they using Oxford, Initio, Prolific, or something else for Firewire/1394?

Are they using Cypress, NEC, Genesys Logic, or something else for USB2?

Are there seperate Firewire/1394 and USB2 chipsets, or is it a combo Firewire+USB2 chipset?

I know someone mentioned that they used to use Epson for Firewire and NEC for USB2, but that was for the PX-716UF and before. Does that still apply to later model external drives, after the redesign to the new case?

It differs indeed by type of enclosure.

The one used for the 716UF (NEC and EPSON):

The newer style case (INITIO and AGERE):