I was fiddiling with a CECH-2501A PS3 I have and it seems that because of the integrated drive logic in this revision (that's to say, the BD-ROM processor and EEPROM are integrated in the main mobo), it seems like the drive is just a case for the disc grabbing motor thing and the laser deck. Even the ROHM PWM is integrated. Another interesting thing I found was that I found, unusually, Samsung XD RDRAM instead of Elpida on my JSD-001 board which is normally there. IDK if its because Pegatron made it and not Foxconn, but its interesting nonetheless. Any odd things you've found in your PS3? I know I found a dead, tiny spider in mine
I once had a CECH-E01 unit with a COK-002 motherboard. It had a weird syscon ID which matched that of a SEM-001(CECH-F01) motherboard.