Why did Lenovo use T9xx0 processors in the T400?

I have a T400 on the way, and the one thing I'm slightly disappointed with is that it's got a T9400. I don't understand why they used the Intel T-series processors at all when they all have P-series listed in the parts page. A P9500 would've given the same performance- 2.53 ghz, 1066 mhz, 6mb cache- all while consuming 10W less.

Will there be a noticeable difference in battery life compared to a P-series processor?

What is Idle States that P8xx0 processors have?

 

I'll have to check idle states(if you tell me how) when my T400(P8400) and X200(P8600) get back from repairs. I'll have to redo some research, but I'm just about certain I've seen someone post up that they swapped in a P9700 into a T400 and it worked just fine. It was an upgrade I've been considering.

 

when the t400 first came out, there were only p8xx0 processors and t9xx0 processors. And also, when the p9xx0 processors came out they were still more expensive than their t9xx0 counterparts.

 

This is true... looking on Fleabay a little while ago seems to indicate that the P9700 goes for about the same price as the T9900 does... around $450USD or so.

I did a little digging and found this thread which seems to confirm that the P9700 will work in a T400 without any BIOS modding or any other issues: http://forum.notebookreview.com/lenovo-ibm/398705-p9700-t400.html

 

P9700 was a factory cpu. It should work fine.

I definitely will leave the T9400 in. Looks like a $200+ upgrade to go to a P9500 which is the equivalent.

I'd also void the 2yrs left on my warranty.

 

Definitely the $$$. Unless you originally got a super slow (and cheap) T-series chip, I find no reason to upgrade to go with the 10W diff.

 

The T9400 in my W500 performs gives about the same battery time as my T500 with the P8700 CPU when both are used on integrated graphics card mode. A LED LCD would give you far more battery time difference than a P9xxx versus T9xxx.

The T9400 CPU is actually quite efficient in terms of power use and thermal management. Under most condition you would not notice a marginal increase in battery time. In my opinion, don't waste the money.

The difference would show itself if you constantly run the laptop with full cpu usage, which for most people is quite rare.

 

I don't plan on changing it for the plethora of reasons discussed here. You're right that 10W is only at full load.

How much more power efficient is the led display? My T400 will have the 300nit LG screen so I don't expect to have it at more than 60-70% brightness in most situations.

 

it gives about 5 to 8% battery power time difference at full brightness on a 15.4 inch machine.

 

Okay... this kinda leads into a related question. I'll be interested in upgrading my T400's CPU down the road, so... P9700, or T9900? 2.8GhZ vs 3.06GhZ, same cache, and 10W TDP difference? Which would be the better choice, given both are going to be about the same as far as cost? I'm pumping up from a P8400, so in my case I think the upgrade could very well be worth it.