Why are 3570K and 3770K both specified @ 77 W TDP?

[Fjodor2001]

Hi,

I just wonder why Intel Ivy Bridge 3570K and 3770K both are specified at 77 W TDP?

In reality, isn't the TDP for 3570K lower than for 3770K? If I remember correctly the difference is like 5-10 W?

 

[ShintaiDK]

Hi,

I just wonder why Intel Ivy Bridge 3570K and 3770K both are specified at 77 W TDP?

In reality, isn't the TDP for 3570K lower than for 3770K? If I remember correctly the difference is like 5-10 W?

Yes and no. 2 chips aint identical. So some 3770 can use less power than some 3570. But overall yes, the trend goes todays 3770 using more.

Family TDP groups. Else you would basicly have to make a new TDP for every single model and revision. Imagine a theroretical 3770 as 77W, 3570 as 72W, 3540 as 68W and so on. OEMs wants to have a few TDP groups to design after. They just want 77W, 65W, 45W etc. So a 46W chip ends in the 65W group.

Another last thing to complicate it even more. They turboburst by TDP as well. So the lower chips in the family group got better chance of full turbo.

 

[Lonyo]

Same reason the 2500k and 2700k were both 95w.
Intel does TDP more by family than per specific chip.
It allows for variances in production and also helps simplify things for system designers and motherboard manufacturers.
They have a specific (typically overestimated) power figure to aim for that will allow them to comfortably support any Intel processor within that family.

 

[Concillian]

TDP is in larger "bins" than just a specific CPU so the motherboard makers know how many phases they need and such.

This is why the boxes say 95W on them. Because the mobo makers have to make a Z/H 77 motherboard with enough power on tap for Sandy Bridge. The next lower "bin" is 65W, and the highest tier Ivys don't quite make that.

It also gives them room to up the voltage on a dud chip and they can still sell it as a 3570.

 

[Fjodor2001]

Ok, thanks. For people striving to build a low power silent PC the "real" TDP may be of interest though. I.e. in that case it might be a better option to go for the 3570K, which may have ~10 W less TDP on average than a 3770K.

 

[BallaTheFeared]

I think it also has to do with OEM hotbox cooling ratings.

I can't give any exact information, but I believe it's something like a rating system for how much cooling is required for operation in a system that has a high ambient temp.



Dunno if that's true or not though.

 

[DaveSimmons]

Ok, thanks. For people striving to build a low power silent PC the "real" TDP may be of interest though. I.e. in that case it might be a better option to go for the 3570K, which may have ~10 W less TDP on average than a 3770K.

"On average" under load, at idle, or what?

It might not be that clear-cut. The 3770K might be using 10 watts more under load, but doing more work. So the work gets done sooner and the 3770K drops back to idle before the 3570K.

If you're never doing anything processor-intensive, you can just ignore the more expensive 3770K and possibly the 3570K too, a dual-core Pentium is all you need for a media playback HTPC.

 

[Puppies04]

Ok, thanks. For people striving to build a low power silent PC the "real" TDP may be of interest though. I.e. in that case it might be a better option to go for the 3570K, which may have ~10 W less TDP on average than a 3770K.

It isn't that simple TBH, if this imaginary "low power silent PC" which for some reason is going to be spec'd with either a full fat I5 or I7 is going to be running programs which primarily respond very well to an I7s hyperthreading you could theoretically underclock the I7 and still outperform the I5 while using the same or less juice.

 

[Fjodor2001]

"On average" under load, at idle, or what?

Under load of course. The TDP is always specified at full load.

When idle, tests have shown that there is little difference between the various Intel CPU models (of the same "generation"). See e.g. http://forums.anandtech.com/showthread.php?t=2146290. But that's a different story.

It might not be that clear-cut. The 3770K might be using 10 watts more under load, but doing more work. So the work gets done sooner and the 3770K drops back to idle before the 3570K.

Sure, but you still have to design your PC to handle the worst case, which is the CPU running at full load and the associated TDP. So you have to take that into account when deciding on cooling solutions etc, which is important when building quiet/silent low power systems.

Also, I agree that it's a trade off between CPU performance requirements vs low TDP and possibility to build a silent system. But my point is just that when building a silent system it might be interesting to know that the TDP of the 3570K will be lower than for the 3770K, despite them both officially being specified at 77 W TDP.

 

[Don Karnage]

Hyperthreading is a Mythical creature that is used by intel for marketing purposes.

 

[Stoneburner]

Hyperthreading is a Mythical creature that is used by intel for marketing purposes.

I had the original HT processor, the p4b 3.06ghz. Back then, HT was largely mythical.

 

[Fjodor2001]

It isn't that simple TBH, if this imaginary "low power silent PC" which for some reason is going to be spec'd with either a full fat I5 or I7 is going to be running programs which primarily respond very well to an I7s hyperthreading you could theoretically underclock the I7 and still outperform the I5 while using the same or less juice.

Sure, you can possibly find such use cases. Not sure how common they are though. And I'm not sure how much you'd have to underclock the 3770K to reach ~10 W lower TDP - possibly quite a bit. And remember that it would affect single threaded performance negatively, which is more important to most people. Not to mention that the 3770K is $100 more expensive than the 3570K.

So for most people I don't think it's a very good solution. But that's of course highly individual depending on what you intend to use your computer for.

 

[Puppies04]

Sure, you can possibly find such use cases. Not sure how common they are though. And I'm not sure how much you'd have to underclock the 3770K to reach ~10 W lower TDP - possibly quite a bit. And remember that it would affect single threaded performance negatively, which is more important to most people. Not to mention that the 3770K is $100 more expensive than the 3570K.

So for most people I don't think it's a very good solution. But that's of course highly individual depending on what you intend to use your computer for.

I think you missed the first point in my post. Pretty much nobody is going to use either of those CPUs in a "silent low power pc" so the point is moot.

 

[paperwastage]

Under load of course. The TDP is always specified at full load.

When idle, tests have shown that there is little difference between the various Intel CPU models (of the same "generation"). See e.g. http://forums.anandtech.com/showthread.php?t=2146290. But that's a different story.

doesn't turbo boost allow the CPU to scale up the frequency until it bumps into the TDP limit (and other limits)?

so a "regular" SB/IB CPU with all the default options/mobo options could all hit 95W/77W (or neighborhood) at load

(of course, with the right mobos, you can turn turbo boost off and try undervolting /other stuff to keep a CPU below a certain TDP that you choose)

 

[Hulk]

I had the original HT processor, the p4b 3.06ghz. Back then, HT was largely mythical.

I had a different experience with the P4-3.06. While it wasn't a fast processor by today's standards I do remember that HT made a huge difference when running two applications at the same time. For example, I could transcode video and the PC was still relatively responsive. With my previous no HT P4 the transcode would totally bog down the system to the point of it being pretty unusable.

 

[philipma1957]

well if you want a silent htpc you should think more with the i5 2500t. i have two builds with them and they are really quiet. if you want the newer one it will be the i5 3570t . i have one build that uses a sapphire 7750 ultimate gpu with no gpu fan. i have the second with an xfx hd 6870 double d gpu i can set the fan at 15% unless I want to game. these are nice builds both are very quiet one use 45 to 48 watts to watch a movie in blu ray the other uses 75 watts due to the better card.

 

[IntelUser2000]

I had a different experience with the P4-3.06. While it wasn't a fast processor by today's standards I do remember that HT made a huge difference when running two applications at the same time. For example, I could transcode video and the PC was still relatively responsive. With my previous no HT P4 the transcode would totally bog down the system to the point of it being pretty unusable.

Hyperthreading was OK for the "C" chips. They got worse when they transitioned to Prescott and got a bad rep there. Then they improved a bit with Presler. It wasn't really "fixed" until Nehalem.

 

[Fjodor2001]

I think you missed the first point in my post. Pretty much nobody is going to use either of those CPUs in a "silent low power pc" so the point is moot.

That completely depends on what cooling solution you go for. If you choose one with heat pipes from the CPU to the chassis which has heat dissipating metal fins you can build a completely silent system and still use CPUs with higher TDP. See for example:

http://www.silentpcreview.com/Streacom_FC5_OD_Case

However that chassis is designed to handle CPUs up to around 65 W TDP. So the 3570K is borderline but will probably be fine since in reality is has a TDP around ~65-70W (even though it officially is specified at 77 W TDP). But the 3770K at ~77 W TDP may be too much. And Sandy Bridge 2500K/2600K at 95W TDP (lower for the 2500K in reality) is most likely too high.

 

[Fjodor2001]

Actually, there does seem to be similar fanless chassis:es (with heatpipes + cooling metal fins) that do accept CPUs up to ~80-95 W. See for example:

http://www.silentpcreview.com/HDPLEX_H3.SODD

So you could possibly build a completely silent system even with the 3770K. Nice! :awe: