Why PCB Swaps make hd no detect ?

[indhay]

I have 2 hd Hitachi 500GB, having same MLC, P/N, Model, but different
S/N ( HD 1 : JQO2JZDH, HD 2 : JQO1TD2H ).
conditions of both normal and detect BIOS

today I tried swapping pcb hd, but after my exchange, my hd is not readable in the BIOS.

number PCB 1: OA72937 BA3786 M5Y044 AOB1
number PCB 2: OA72937 BA3786 K60043 3HB7

Anybody can give me a good/nice reason?
thank for all..

[loki]

Did you swap the ROM / NV-RAM Chip over (ie 8-pin chip) on the pcb's?

Loki

[indhay]

Did you swap the ROM / NV-RAM Chip over (ie 8-pin chip) on the pcb's?

Loki

No, i swap the PCB only

[pcimage]

That is why is doesn't work

[indhay]

That is why is doesn't work

yeah.. how about ur opinion?

[pcimage]

Do as loki says