Surface Pro 3 throttling

The CPU in the Pro 3 models are different than the models used in the Pro 2.  Even though they are "Haswell" chips, they are built completely different and are not the same type that can be installed in a desktop or laptop (which the Pro and Pro 2 did use).  They are flatter in design and wider to actually increase cooling capability (at least, designed to do so) and that may not be the case.

That's just not true in any way. All three versions run "ultrabook" class CPUs, the same type you would see in a Macbook Air. It's possible that MS is using a different heat spreader on the chip to fit their designs, but the CPUs themselves are exactly the same.

The original SP2 units use an Intel 4200U, while later production runs (anything produced after December 2013) have the 4300U, which was the replacement from Intel when the 4200U was discontinued. The SP3 uses this same chip, but has more severe thermal constraints compared to the SP2 due to its smaller chassis and single fan.

It's a deliberate design tradeoff. Personally I disagree with the choice, but I imagine the average user is going to prefer lighter over more sustained CPU power.

The surprise/confusion/disappointment that certainly I feel, is that I expected the Pro 3 to perform at least as well as the Pro 2 when it comes to gaming.  Because of the aggressive throttling going on (far more aggressive than that of the Pro 2) it measurably does not perform as well over sustained periods (even as low as over a few minutes).

To use Diablo 3 as an example, I tested it last night on both the Pro 2 and 3.  On the Pro 2 at 1920x1080 with all settings LOW and "Low FX" turned on to improve performance - FPS remained pretty steadily in the high 20s or even 30, even when fighting lots of monsters.  Not stellar by any means - nobody expects the Surface to be a Razer Blade - but it is playable.

On the Pro 3, with the resolution lowered to 1920x1080, and game performance settings the same as the Pro 2, performance starts out the same, but after maybe 5-10 minutes, I'm down to 10-12 FPS.  Borderline unplayable.  I switched back to the desktop for a few minutes, and when I switched back to the game, performance had improved again.  So at least for me the throttling was temporary (as I would think it should be).  It's not a good experience to have to interrupt my gaming every 5 or 10 minutes to give the machine a few minutes to cool down again.

The Pro 3 was on a desk and well ventilated.

It's not awful, but it is a measurable experience downgrade.  I'd return the Pro 3 and wait for the i7 version, if I thought that would improve things, but my fear is that if the i7 model exhibits similar throttling behaviour, then the experience is going to be much the same, and I'll have blown a further $250 for nothing.

I understand everything you are saying about the new chassis, different components etc - that all makes perfect technical sense.  This issue is not going to impact the vast amount of users.  But from a marketing point of view, the Pro 3 has been portrayed as better than what came before.  For most things, it is, but for sustained performance, it is a downgrade.  It's very very disappointing, because this machine is so utterly amazing in every other way.

Microsoft even advertise the Pro 3 for gaming, although there is no mention of which variant they are talking about.....

http://www.microsoft.com/surface/en-us/why-surface/for-gaming

Every part of me wants to keep this wonderful machine, which is why I wish Microsoft would say something about this issue.  "Hey, we're aware of the throttling and the concern it's causing some users.  We're looking into ways to tune the behaviour."  Even if they come back and say "We're sorry but this is the design and we cannot change it without making the risk of physical thermal damage too great" then at least that would be something, and I could make my final decision to keep or return the machine.

You could use the Intel Extreme Tuning Untility, which is commonly used to control overclocking features on Intel motherboards, but it also has the ability to tweak the way Turbo boost works, which could help you.

https://downloadcenter.intel.com/Detail\_Desc.aspx?agr=Y&DwnldID=23743&ProdId=3483&lang=eng&OSVersion=Windows%208.1\*&DownloadType=Utilities%2C%20Tools%20and%20Examples

Probably meant degrees.  CPUs usually do not go over 125 degrees Fahrenheit and if they do, they shut themselves down.  There is a temperature sensor that controls that and it shuts down the computer instantly and will not allow the computer to turn on until the temperature is below a certain level.

That degree setting can be different between computers.  The motherboard usually controls that.

Seems backwards that Diablo 3 runs fine on the Service Pro 2 (SP2), same settings enabled. From what people are saying and running some of my own test, the SP3 throttles around 90 degrees Celsius, much like the SP2. The difference being, the SP2 only throttles down till it gets around 80 degrees Celsius where the SP3, needs to throttle down till it reaches less than 60 degrees before ramping up. major difference here. 

Don't just take my word for it - http://www.anandtech.com/show/8077/microsoft-surface-pro-3-review/3

do you really mean degrees Celsius? 90 Degrees Celsius close to 195 degrees Fahrenheit! The Anandtech  article has much lower temperatures