Variable what? "Bom" is not a standard "electronics" term. In my shop we use it on the consulting side of the business when we submit a bid for a new contract. There it stands for a "bill of materials".
Please clarify. Did you mean OEM? If so, then that makes sense.
Too bad it won't be available in the states.
I don't know how many other companies do this (two very different models, made by two different OEM suppliers, clearly using different designs but with the same model number) but I find this very frustrating.
GW's take on the CX650, fairly impressive considering the budget constraint
"Fairly impressive"? I don't agree. The ATX Form Factor standard for ATX power supplies establishes the "
minimum" requirements that all ATX PSUs, even budget models,
must meet in order to be ATX compliant. That GW CX650 failed!
"Hold-up time" is the amount of time a PSU maintains full continuous output voltages during a power interruption. The ATX Form Factor standard
requires ATX compliant PSUs to "hold up" output power for at least 17ms during such power interruptions. Note as seen
here on page 20, section 3.2.9, that is a "
requirement", not a "recommendation" as that Tom's article and JG state.
That CS 650W supply failed miserably, holding output for only 8.3ms

- less than half the required time! That means any loss of power (or a simple dip or sag below 90VAC) of even 10ms (which is MUCH faster than the human eye can detect) will result the computer suddenly crashing, potentially resulting in lost data and/or a corrupt drive.
Power dips (opposite of spikes) and sags (opposite of surges) and brownouts (long duration sags) are much more common than most people think - even with stable power grids. And such power anomalies don't have to originate off the grid. A refrigerator or AC unit cycling on, for example, can cause a voltage drop on that circuit.
Consumers need to expect - or rather
demand that
any PSU claiming to be ATX Form Factor compliant
must meet the minimum specs laid out in that standard. PERIOD!
That means that entry level PSUs, that is, those built with "budget constraints" must meet those
minimum specs too. It is up to the upper tier models to exceed those specs - which many do, with ease!
That Corsair failed. It is not ATX compliant. I do not recommend anyone buy it. If you do, make sure you put it on a "good" UPS with AVR. And keep regular backups of your data.