The Intel Broadwell Review Part 2: Overclocking, IPC and Generational Analysis
by Ian Cutress on August 3, 2015 8:00 AM ESTGenerational Tests: Office and Web Benchmarks
For this review, as mentioned on the front page, we retested some of the older CPUs under our new methodology. We did this testing at stock frequency as well as the IPC testing to see the ultimate real world result when you add in HyperThreading and frequency into the mix. If you recall back in our Devil’s Canyon i7-4790K review, the new high 4.4 GHz frequency of the i7-4790K was a tough one to beat for the newer architecture purely because any IPC gains are nullified by the older processor having a lot more frequency. With the Broadwell based i7-5775C being at 3.7 GHz and only 65W, this is a tough task. But what about if you are still running the Sandy Bridge based i7-2600K?
Some users will notice that in our benchmark database Bench, we keep data on the CPUs we’ve tested back over a decade and the benchmarks we were running back then. For a few of these benchmarks, such as Cinebench R10, we do actually run these on the new CPUs as well, although for the sake of brevity and relevance we tend not to put this data in the review. Well here are a few of those numbers too.
With some of these benchmarks, due to applications using new instruction sets, having the newer processors with the new instructions can make a lot of difference. Even in Cinebench R10, moving from the Core 2 Quad Q9550 to a Broadwell can get a 2.5x speed-up in this old software.
For the rest of our CPU benchmarks, here is what the landscape looks like with the most recent architectures. All of our benchmark results can also be found in our benchmark engine, Bench.
Office Performance
The dynamics of CPU Turbo modes, both Intel and AMD, can cause concern during environments with a variable threaded workload. There is also an added issue of the motherboard remaining consistent, depending on how the motherboard manufacturer wants to add in their own boosting technologies over the ones that Intel would prefer they used. In order to remain consistent, we implement an OS-level unique high performance mode on all the CPUs we test which should override any motherboard manufacturer performance mode.
Dolphin Benchmark: link
Many emulators are often bound by single thread CPU performance, and general reports tended to suggest that Haswell provided a significant boost to emulator performance. This benchmark runs a Wii program that raytraces a complex 3D scene inside the Dolphin Wii emulator. Performance on this benchmark is a good proxy of the speed of Dolphin CPU emulation, which is an intensive single core task using most aspects of a CPU. Results are given in minutes, where the Wii itself scores 17.53 minutes.
WinRAR 5.0.1: link
Our WinRAR test from 2013 is updated to the latest version of WinRAR at the start of 2014. We compress a set of 2867 files across 320 folders totaling 1.52 GB in size – 95% of these files are small typical website files, and the rest (90% of the size) are small 30 second 720p videos.
3D Particle Movement
3DPM is a self-penned benchmark, taking basic 3D movement algorithms used in Brownian Motion simulations and testing them for speed. High floating point performance, MHz and IPC wins in the single thread version, whereas the multithread version has to handle the threads and loves more cores.
FastStone Image Viewer 4.9
FastStone is the program I use to perform quick or bulk actions on images, such as resizing, adjusting for color and cropping. In our test we take a series of 170 images in various sizes and formats and convert them all into 640x480 .gif files, maintaining the aspect ratio. FastStone does not use multithreading for this test, and results are given in seconds.
Web Benchmarks
On the lower end processors, general usability is a big factor of experience, especially as we move into the HTML5 era of web browsing. For our web benchmarks, we take four well known tests with Chrome 35 as a consistent browser.
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name99 - Monday, August 3, 2015 - link
Well think about WHY these results are as they are:- There is one set of benchmarks (most of the raytracing and sci stuff) that can make use of AVX. They see a nice boost from initial AVX (implemented by routing each instruction through the FPU twice) to AVX on a wider execution unit to the introduction of AVX2.
- There is a second set of benchmarks (primarily winRAR) that manipulate data which fits in the crystalwell cache but not in the 8MB L3). Again a nice win there; but that's a specialized situation. In data streaming examples (which better described most video encode/decode/filtering) that large L4 doesn't really buy you anything.
- There WOULD be a third set of benchmarks (if AnandTech tested for this) that showed a substantial improvement in indirect branch performance going from IB to Haswell. This is most obvious on interpreters and similar such code, though it also helps virtual functions in C++/Swift style code and Objective C method calls. My recollection is that you can see this jump in the GeekBench Lua benchmark. (Interestingly enough, Apple's A8 seems to use this same advanced TAGE-like indirect predictor because it gets Lua IPC scores as good as Intel).
OK, no we get to Skylake. Which of these apply?
- No AVX bump except for Xeons.
- Usually no CrystalWell
So the betting would be that the BIG jumps we saw won't be there. Unless they've added something new that they haven't mentioned yet (eg a substantially more sophisticated prefetcher, or value prediction), we won't even get the small targeted boost that we saw when Haswell's indirect predictor was added. So all we'll get is the usual 1 or 2% improvement from adding 4 or 6 more physical registers and ROB slots, maybe two more issue slots, a few more branch predictor slots, the usual sort of thing.
There ARE ideas still remaining in the academic world for big (30% or so) improvements in single-threaded IPC, but it's difficult for Intel to exploit these given how complex their CPUs are, and how long the pipeline is from starting a chip till when it ships. In the absence of competition, my guess is they continue to play it safe. Apple, I think, is more likely to experiment with these ideas because their base CPU is a whole lot easier to understand and modify, and they have more competition.
(Though I don't expect these changes in the A9. The A7 was adequate to fight off the expected A57; the A8 is adequate to fight off the expected A72; and all the A9 needs to do to maintain a one year plus lead is add the ARMv81.a ISA and the same sort of small tweaks and a two hundred or so MHz boost that we saw applied to the A8. I don't expect the big microarchitectural changes at Apple until
- they've shipped ARMv81.a ISA
- they've shipped their GPU (tightly integrated HSA style with not just VM and shared L3, but with tighter faster coupling between CPU and GPU for fast data movement, and with the OS able to interrupt and to some extent virtualize the GPU)
- they're confident enough in how wide-spread 64-bit apps are that they don't care about stripping out the 32-bit/thumb ISA support in the CPU [with what they implies for the pipeline, in particular predication and barrel shifter] and can create a microarchitecture that is purely optimized for the 64-bit ISA.
Maybe this will be the A10, IF the A9 has ARMv8.1a and an Apple GPU.)
Speedfriend - Tuesday, August 4, 2015 - link
"The A7 was adequate to fight off the expected A57;"In hindsight the A7 was not very good at all, it was the reason that Apple was unable to launch a large screen phone with decent battery life. Look at he improvements made to A8, around 10% better performance, but 50% more battery life.
Speedfriend - Tuesday, August 4, 2015 - link
"they've shipped their GPU" by the way, why do you expect them to ship their own GPU and not use IMG's. The IMG GPU have consistently been the best in the market.nunya112 - Monday, August 3, 2015 - link
by the looks of it. the 4790K seems to be the best CPU. until skylake that is. but even then I doubt there will be much improvementnunya112 - Monday, August 3, 2015 - link
unless u have the older ivy's then yeah maybe worth it ?TheinsanegamerN - Monday, August 3, 2015 - link
Nah. the older ivys can be overclocked to easily meet these chips. the IPC of broadwell is overshadowed by a 400mhz lower clock rate on typical OC. only reason to upgrade is if you NEED something on the new chipset or are running some nehalem-era chip.Teknobug - Monday, August 3, 2015 - link
Ivy's are the best overclockers.TheinsanegamerN - Monday, August 3, 2015 - link
Sandy overclocked better than ivy,Hulk - Monday, August 3, 2015 - link
Ian - Very nice job on this one! Thanks.Meaker10 - Monday, August 3, 2015 - link
A slight correction, on the image of crystal well it is the die on the left (the much larger one) which is the cache and the small one is the cpu on the right.