Intel’s Sandy Bridge i7-2820QM: Upheaval in the Mobile Landscape
by Jarred Walton on January 3, 2011 12:00 AM EST- Posted in
- Laptops
- Intel
- Sandy Bridge
- Compal
Performance and Power Investigated
Given all the performance packed into the i7-2820QM, worst-case heat and noise levels should still be similar to what we encountered with Clarksfield. Idle power is good, but if you want to do some heavy processing or gaming what happens? We connected the Compal system to a Kill-A-Watt device to check power draw under various loads, as well as testing battery life while looping a graphics intensive application. We’ve seen NVIDIA and AMD GPUs really curtail performance on DC power, but has Intel done the same?
We’ve created a table of power draw at the outlet for several usage scenarios, as well as the calculated power requirements on DC based on the 71Wh battery. We’ve also included the performance figures for the tasks where applicable, to see if performance throttling is in effect when on battery power. We used the “Balanced” power profile for the AC tests, and the Power Saver profile (but still allowing the CPU to go to 100%) for battery tests. For the graphics test, we enabled the “Maximum Battery Life” setting as well as the “Balanced” setting—the graphics tests on AC were done using the “Maximum Performance” setting.
| Power/Performance Under AC/DC | ||
|
Power at Outlet / Calculated DC Power |
Performance | |
| Idle | 12-13W | N/A |
| Idle (DC) | 9.04W | N/A |
| Internet | 14-31W | N/A |
| Internet (DC) | 10.24W | N/A |
| 3DMark06 | 48-70W | 5285 |
| 3DMark06 (DC) MaxBat | 23.61W | 2800 |
| 3DMark06 (DC) Balanced | 41.18W | 5184 |
| H.264 Playback | 20-21W | N/A |
| H.264 Playback (DC) | 16.38W | N/A |
| Cinebench 11.5 SMP | 70-89W | 5.72 |
| Cinebench 11.5 SMP (DC) | 59.17W | 5.09 |
Watching power draw and CPU clocks (using CPU-Z) during the tests was rather interesting. There’s not much going on in the idle test; looking at the numbers, AC power use is about 36% higher than the DC calculated power use. Most likely extra power-saving features are in effect under DC power.
In the Internet test (under AC), while the web pages are loading the system used anywhere from 18-31W. Once all four pages have finished loading, however, power would settle down to 14W—just slightly higher than the idle power draw. That’s quite impressive, given the Flash content on the active page, and that’s reflected in the only slightly higher calculated power draw for Internet battery life vs. idle. Also of note is that the CPU clock speed never even hit 2.3GHz—let along the maximum 3.4GHz—during the Internet test, at least not that we could detect. We could see it reach 1.6GHz for a few seconds, and then it would settle back to 800MHz.
The H.264 playback test is another example of low CPU clocks and utilization through the test. The initial loading of the x264 movie would bump clock speeds up, but then the CPU would drop back to the minimum 800MHz and stay there. Power draw is definitely higher than the idle/Internet tests, but 20-21W isn’t too shabby for a 17.3” notebook. And then we get to the power hungry tests, simulating gaming and heavy CPU use.
3DMark06 power requirements are generally similar to gaming results, with the wide spread being typical. Tests 1, 3, and 4 averaged power draw closer to 53W, while test 2 (the Firefly Forest) was nearly 10W higher on average. Turbo Boost—on both the CPU and GPU—is very likely in play, but we didn’t have a good way of measuring real-time clock speeds during the tests. We tested battery graphics performance using two settings; first is the “Maximum Battery Life” setting, which results in roughly half the performance compared to running on AC. The second mode is labeled “Balanced”, which improves the score quite a bit—at the cost of power consumption.
Based on the 3DMark06 results, plugging in improves graphics performance by 2-82%, depending on what graphics power saving setting you select. You’ll definitely want to run the higher performance GPU mode if you actually want to play games, as otherwise frame rates will drop into the low 20s or upper teens on most titles. With the “Balanced” or “High Performance” GPU setting, gaming performance is reasonable even on battery power, but it puts enough of a load on the battery that you won’t be able to last more than around 90-100 minutes. If you happen to have a game where you only need the power saving performance mode, though, you should be able to get gaming battery life up to three or perhaps even four hours (depending on the game).
Finally, we’ll wrap up this discussion by looking at maximum CPU loads. In the Cinebench test, quad-core Turbo is interesting to watch; running the CB11.5 SMP benchmark, at first all of the cores start at the maximum 3.10GHz speed—blisteringly fast for a notebook! About 11 seconds in to the test, the core speed drops to 3.0GHz, where it remained until 39 seconds; then it dropped to 2.9GHz, and at around 54 seconds the speed dropped briefly (1-2 seconds) to 2.8GHz before settling in at 2.7GHz for the remainder of the test. If you happen to run heavily-threaded benchmarks continuously, the first run will usually show about 10% higher performance thanks to the initial thermal headroom, but the lowest Cinebench SMP and x264 encoding scores that we measured are still within 10% of the maximum score, which is very impressive for notebook hardware.
At the highest point in the test, power draw for the notebook peaked at 89W; once the speed settled at 2.7GHz (which it appears the notebook could sustain indefinitely in our 70F testing environment), power draw was steady at 70W. Switch to battery power and the Power Saver profile, and performance did drop slightly but not as much as you’d expect. We measured 5.09 PTS while running off the battery, so plugging in nets you up to 12% better performance. Like gaming, battery life under a heavy CPU load is going to be much lower than our other tests, and we measured just 72 minutes. Then again, compare that with some of the other high-end notebooks we’ve looked at in the past, which managed a similar 72 minutes with no load whatsoever.
One thing to keep in mind is that the effectiveness of Intel’s Turbo Boost technology does depend on the cooling equipment. While the Compal sample runs reasonably cool—we’ll check temperatures on the next page—we have definitely seen larger, more robust cooling solutions. The profile of the Compal chassis is generally flat, so that limits the size of the fan(s) and the amount of airflow. Something like the ASUS G73 chassis has proven quite effective at running high-end mobile components in the past, and we suspect that better cooling will result in the CPU running closer to the maximum Turbo limits more of the time. We’ll have to wait for sample notebooks to confirm our suspicions, but we’ve seen it in the past with Clarksfield and Arrandale, so there’s no reason Sandy Bridge would behave differently.
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mtoma - Monday, January 3, 2011 - link
Something like Core i7 1357M could make Win 7 tablets temporarily viable. Remember that in the ultra portable space the big words are: multitasking, dual core processors (like Cortex A9). So, realistically, we need ULV dual-core Sandy Bridge.JarredWalton - Monday, January 3, 2011 - link
The i7-640M runs at 1.2GHz minimum and 2.26GHz maximum. The i7-2657M runs at 1.6GHz minimum and 2.7GHz maximum. (Actually, minimum on all the Core 2nd Gen is 800MHz when you aren't doing anything that needs more speed.) That would be 33% faster base speed and up to 19% higher max speed, just on clock speeds alone. However, you forgot to factor in a round 20-25% performance increase just from the Sandy Bridge architecture, so you're really looking at anywhere from 19% (bare minimum) to as much as 66% faster for normal usage, and things like Quick Sync would make certain things even faster.DanNeely - Monday, January 3, 2011 - link
You've got a limited range of TDP that any given architecture will be good in. According to Intel (at the time of the atom launch) things start getting rather ragged when the range gets to 10x. Until Core2 this wasn't really an issue for Intel because the p3 and prior's top end parts had sufficiently low TDPs that fitting the entire product line into a single architecture wasn't a problem. It didn't matter much in the P4 era because the Pentium-M and Core 1 were separate architectures and could be tuned so its sweet spot was significantly lower than the desktop P4. Beginning with Core2 however Intel only had a single architecture. The bottom tier of ULV chips suffered due to this, and on the high end the fact that overclocking (especially voltage OCing) was very poor on the performance gain/increased power consumption scale.The atom is weak as you approach 10W because it was designed not as a low end laptop part (although Intel is more than willing to take your money for a netbook); but to invade ARM's stronghold in smartphones, tablets, and other low power embedded systems. Doing that requires good performance at <1W TDP. By using a low power process (instead of the performance process of every prior Intel fabbed CPU) Moorestown should finally be able to do so. The catch is that it leaves Intel without anything well optimized for the 10-15W range. In theory the AMD Bobcat should be well placed for this market, but the much larger chunk of TDP given to graphics combined with AMDs historic liability in idle power make it something of a darkhorse. I wouldn't be surprised if the 17W Sandybridge is able to end up getting better battery life than the 10W Bobcat because of this.
Kenny_ - Monday, January 3, 2011 - link
I have seen in the past that when Mac OS X and Win 7 are run on the same machine, Mac OS X can have significantly better battery life. Is there any chance we could see what Sandy Bridge does for battery life under Mac OS X?QChronoD - Monday, January 3, 2011 - link
This was a test machine that intel cobbled together. Give it a few weeks or months after some retail machines come out, and then I'm sure that someone in the community will have somehow shoehorned OSX onto one of the machines. (Although I don't know how well it would perform since they'd probably have to write new drivers for the chipset and the graphics)cgeorgescu - Monday, January 3, 2011 - link
I think that in the past we've seen MacOS and Win7 battery life comparison while running on the same Mac, not on the same Acer/Asus/Any machine (cause MacOS doesn't run on such w/o hacks). And I suspect Apple manages better power management only because they have to support only few hardware configurations (so doing optimizations especially for that hardware), it's a major advantage of their business model.It's like with the performance of games on Xbox and the like... The hardware isn't that impressive but you write and compile only for that configuration and nothing else: you're sure that every other machine is the same, not depending on AMD code paths, smaller or larger cache, slower or faster RAM, that or the other video card, and so on...
Aside power management in macs, to see what Sandy Bridge can do under MacOS would be frustrating... You know how long it takes until Jobs fits new stuff in those MBPs. Hell, he still sells Core2 duo.
Penti - Monday, January 3, 2011 - link
Having fewer configurations don't mean better optimized graphics drivers they are worse. Having only intel doesn't mean the GCC compiler only outputs optimized code. It's a compiler AMD contribute to among others and there's no such thing as AMD code paths, there is some minor difference in how it manages SSE but that's it. Most is exactly the same and the compiler just optimizes for x86 not a brand. If it supports the same features it is as optimized. Machine Code is the same. It's not like having a cell processor there.Power management is handles by the kernel/drivers. You can expect SB MacBooks in like this summer. Not too long off. And you might even be seeing people accepting Flash on their macs again as Adobe is starting to move away from their archaic none video player work flow. With 10.2 and forward. Battery/Power management won't really work without Apples firmware though. But you are simply not going to optimize code on a OS X machine like a console, your gonna leave it in a worse state then the Windows counterpart. Apple will also be using C2D as long as Intel don't provide them with optimized proper drivers. It's a better fit for the smaller models as is.
mcdill the pig - Monday, January 3, 2011 - link
Perhaps the issue is more the Compal's cooling system but those max CPU temps (91 degrees celsius) seem high. It may also be that the non-Extreme CPUs will have lower temps when stressed.My Envy 17 already has high temps - I was looking forward to SB notebooks having better thermal characteristics than the i7 QM chips (i.e. no more hot palmrests or ball-burning undersides)....
JarredWalton - Monday, January 3, 2011 - link
This is a "works as designed" thing. Intel runs the CPU at the maximum speed allowed (3.1GHz on heavily threaded code in this case) until the CPU gets too warm. Actually, funny thing is that when the fan stopped working at one point (a cold reboot fixed it), CPU temps maxed out at 99C. Even with no fan running, the system remained fully stable; it just ran at 800MHz most of the time (particularly if you put a load on the CPU for more than 5 seconds), possibly with other throttling going on. Cinebench 11.5 for instance ran about 1/4 as fast as normal.DanNeely - Monday, January 3, 2011 - link
Throttling down to maintain TDP at safe levels has been an intel feature since the P4 era. back in 2001(?) toms hardware demoed this dramatically by running quake on a P4 and removing the cooler entirely. Quake dropped into slideshow mode but remained stable and recovered as soon as the heatsink was set back on top.The p3 they tested did a hard crash. The athlon XP/MP chips reached several hundred degrees and self destructed (taking the mobos with them). Future AMD CPUs had thermal protection circuitry to avoid this fail mode as well.