T420 Identification

[PhoenixR]

I've been offered a T420 lately so I decided to clarify its configuration first but couldn't find a relevant info based on its type number.
I am on T400 right now & from what I have gathered the major key differences between the models are: i3-i7 35W vs Core2D 25W CPUs, integrated Intel OR discreet Nvidia NVS(never both) vs hybrid Intel + AMD (in some types, including mine) GPUs, LED vs CCFL (majority, including mine) screens. Is there a booklet or any other source with this kind of info helping to identify the exact configuration of a given T420(including 420i, 420s, still having just a very vague idea what is the difference between 420/420i/420s) based on its typexxxx-xxx number?

[RealBlackStuff]

Search the web for: lenovo t420 psref
Change t420 for any model you want.
PSREF has all the info you want.

[axur-delmeria]

Use the MTM link at the top of this very website, just below the site banner. It's between HMM-Manuals and Feed.

Enter the MTM without hyphen (e.g. 7676A27). Good luck.

[PhoenixR]

Thanks guys
So I've been able to identify it. The cpu onboard is 2520M. I am thinking upgrade. As far as I see the socket PPGA988 can handle not just sandy bridge but also ivy bridge cpus like 3520,3540 & even quads 3840qm etc. So can I upgrade it with an ivy bridge i7 3... indeed?

& the second part which also got me interested: my T400 with a Centrino sticker runs on P9600 which is a 25W TDP, it is rather quiet & cool. T420 on the other hand runs on 35W cpus but the owners say it is quiet & cool, too. I saw AIDA64 screenshots showing nearly the same cpus temperatures 40+C for both T400 & T420 with fan revs even less maybe for T420. Still on paper 35W is 40% higher than 25W - so is 35W T420 hotter & louder than 25W T400 or not in fact? Has lenovo removed Centrino stickers which attributed to quietness & coolness from all the new models after T400 containing 35W cpus to reflect that the new 35W laptops while having had become more powerful but also noisier & hotter?