Here's the deal, I recently bought a slim ps2 9000x series, only after bying it realizing that it was not compatible with free mcboot. After I thought I might invest in a mod chip, but did not have the right soldering equipment. shortly after my little mishap, I returned my 9000x to the store and bought a refurbished 7000x series for modding. I don't remember where I saw it, but one day when I was browsing the web, I stumbled upon a couple forums talking about how sony has bean downgrading their ps2 console, so much in fact that they even downgraded the power supply. I'm not to sure about to many details, but I did look at the play station website (they still manufacture the slim 7000x series apparently)and did notice a change in the power watts.
7000x: 45w
9000x: 35w
Not to mention the housing is now almost just a brick.
If anyone has any additional info, it would be much appreciated.:)
On the SCPH 90001, The PSU is now internalized within the compact case of the console and has built-in AC adapter.
There is nothing wrong with the other slim PS2 though, except for the V12 with its laser problem due to the overheating of the coils (mostly a problem if modchip is installed), that was fixed in later models.
As long as the Date code on the 90001 is 8b, then your ok to install fmcb.