Comparing IPC: Memory Latency and CPU Benchmarks

Being able to do more with less, in the processor space, allows both the task to be completed quicker and often for less power. While the concept of having multiple cores has allowed many programs to be run at once, such as IM, web, compute and so forth, we are all still limited by the fact that a lot of software is still relying on one line of code after another, pegging each software package to once core unless it can exploit a mulithreaded list of operations. This is referred to as the serial part of the software, and is the basis for many early programming classes – getting the software to compile and complete is more important than speed. But the truth is that having a few fast cores helps more than several thousand super slow cores. This is where Instructions Per Clock (IPC) comes in to play.

The principles behind extracting IPC are quite complex as one might imagine. Ideally every instruction a CPU gets should be read, executed and finished in one cycle, however that is never the case. The processor has to take the instruction, decode the instruction, gather the data (depends on where the data is), perform work on the data, then decide what to do with the result. Moving has never been more complicated, and the ability for a processor to hide latency, pre-prepare data by predicting future events or keeping hold of previous events for potential future use is all part of the plan. All the meanwhile there is an external focus on making sure power consumption is low and the frequency of the processor can scale depending on what the target device actually is.

For the most part, Intel has successfully increased IPC every generation of processor. In most cases, 5-10% with a node change and 5-25% with an architecture change with the most recent large jumps being with the Core architecture and the Sandy Bridge architectures, ushering in new waves of super-fast computational power. As Haswell to Broadwell is a node change with minor silicon updates, we should expect some gain but the main benefit should be efficiency by moving to a smaller node.

For this test we took Intel’s high-end i7 processors from the last four generations and set them to 3.0 GHz and with HyperThreading disabled. As each platform uses DDR3, we set the memory across each to DDR3-1866 with a CAS latency of 9. From a pure cache standpoint, here is how each of the processors performed:

Both Haswell and Broadwell have a small lead through the Level 1 Cache (32kB) and Level 2 Cache (256kB). It all changes from 6MB onwards as a result of the different cache levels between the processors. As the Broadwell based i7-5775C only has 6MB of L3 cache, this seems to effect the 4MB data set range, but between 8MB and 64MB values, the memory latency for Broadwell is substantially lower than any other Intel processor. This comes down to the eDRAM, which sticks around until 128MB.

Most memory accesses happen at lower data set ranges as the system attempts to predict the data needed. When data is not in the L1 cache, it is considered a cache miss and looks for the data in L2. When not in L2, look in L3. When not in L3, look in eDRAM/DDR3. From this perspective, the Broadwell based processors should have a slight advantage when it comes to large amounts of data accesses. Based on our previous testing, this means integrated graphics or high intensity CPU/DRAM workloads such as databases or matrix operations.

Here are the CPU results at 3.0 GHz:

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.

Dolphin Emulation Benchmark

Cinebench R15

Cinebench is a benchmark based around Cinema 4D, and is fairly well known among enthusiasts for stressing the CPU for a provided workload. Results are given as a score, where higher is better.

Cinebench R15 - Single Threaded

Cinebench R15 - Multi-Threaded

Point Calculations – 3D Movement Algorithm Test: link

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. For a brief explanation of the platform agnostic coding behind this benchmark, see my forum post here.

3D Particle Movement: Single Threaded

3D Particle Movement: MultiThreaded

Compression – 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.

WinRAR 5.01, 2867 files, 1.52 GB

Image Manipulation – FastStone Image Viewer 4.9: link

Similarly to WinRAR, the FastStone test us updated for 2014 to the latest version. 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 thus single threaded performance is often the winner.

FastStone Image Viewer 4.9

Video Conversion – Handbrake v0.9.9: link

Handbrake is a media conversion tool that was initially designed to help DVD ISOs and Video CDs into more common video formats. The principle today is still the same, primarily as an output for H.264 + AAC/MP3 audio within an MKV container. In our test we use the same videos as in the Xilisoft test, and results are given in frames per second.

HandBrake v0.9.9 LQ Film

HandBrake v0.9.9 2x4K

Rendering – PovRay 3.7: link

The Persistence of Vision RayTracer, or PovRay, is a freeware package for as the name suggests, ray tracing. It is a pure renderer, rather than modeling software, but the latest beta version contains a handy benchmark for stressing all processing threads on a platform. We have been using this test in motherboard reviews to test memory stability at various CPU speeds to good effect – if it passes the test, the IMC in the CPU is stable for a given CPU speed. As a CPU test, it runs for approximately 2-3 minutes on high end platforms.

POV-Ray 3.7 Beta RC4

Synthetic – 7-Zip 9.2: link

As an open source compression tool, 7-Zip is a popular tool for making sets of files easier to handle and transfer. The software offers up its own benchmark, to which we report the result.

7-zip Benchmark

Overall: CPU IPC

*When this section was published initially, the timed benchmarks (those that rely on time rather than score) were caluclated incorrectly. The text has been updated to reflect the new calculations.

Removing WinRAR as a benchmark that obviously benefits from the eDRAM, we get an interesting look at how each generation has evolved over time. Taking Sandy Bridge (i7-2600K) as the base, we get the following:

As we can see, performance gains are everywhere although the total benefit is highly dependent on the benchmark in question. Cinebench in single threaded mode for example gives a 16.7% gain from Sandy Bridge to Broadwell, however Dolphin which is also single threaded gets a 58.1% improvement. Overall, a move from Sandy Bridge to Broadwell from an IPC perspective gives an average ~21% improvement. That is an increase in pure, raw throughput before considering frequency or any differentiator in core counts.

If we adjust this graph to show generation to generation improvement:

This graph shows something a little bit different. From these numbers:

Sandy Bridge to Ivy Bridge: Average ~5.0% Up
Ivy Bridge to Haswell: Average ~11.2% Up
Haswell to Broadwell: Average ~3.3% Up

Thus in a like for like environment, when eDRAM is not explicitly a driver for performance, Broadwell gives a 3.3% gain over Haswell. That’s a take home message worth considering, but it also affords the difference in performance between an architecture update and a node change.

Cycling back to our WinRAR test, things look a little different. Ivy Bridge to Haswell gives only a 3.2% difference, but the eDRAM in Broadwell slaps on another 23.8% performance increase, dropping the benchmark from 76.65 seconds to 63.91 seconds. When eDRAM counts, it counts a lot.

Overclocking Broadwell Comparing IPC: Discrete Gaming


View All Comments

  • Shadowmaster625 - Monday, August 3, 2015 - link

    I never understood the "pea size" method. Peas come in many different sizes. And it seems to me that the size of a typical pea is rather large. You need something standard, like a bb. They are a standard size, 0.177 caliber, and three of them in a line seems to work best. Reply
  • Pissedoffyouth - Monday, August 3, 2015 - link

    I put a grain of rice size in the middle. get a glasses cloth and rub it on both the heatsink and the heat spreader, and rub it off. Should be a slight tinting left.

    Then put another grain of rice size in the middle and screw the heatsink in. Done.

    You want to use the bare minimum amount of paste.
  • zodiacfml - Monday, August 3, 2015 - link

    Very polarizing CPU. Any ideas why Intel doesn't have Crystalwell in laptops? I don't want a discrete GPU anymore in mobile due to risk of dead GPUs/Mobo after a few years. Reply
  • zodiacfml - Monday, August 3, 2015 - link

    Oh, nevermind! I found them. Reply
  • extide - Monday, August 3, 2015 - link

    They do, but the CPU's with Crystalwell are quite expensive, so most OEM's shy away from them because it is too expensive for a cheap laptop, and then a higher end laptop they put a dGPU in.

    In my next laptop, I want a Iris Pro (w/ Crystalwell) chip, and NO DGPU! I don't want the power consumption, and Iris Pro is plenty enough performance for what I do on a laptop. Unfortunately, it's kinda hard to find high-ish end laptop's with that config. :(
  • Gigaplex - Monday, August 3, 2015 - link

    Before Broadwell, the only way to get Crystalwell was in the mobile chips. Reply
  • varg14 - Monday, August 3, 2015 - link

    Until my pretty much 5 year old Sandy Bridge 2600k that runs between 4.5-5.0ghz PCIE 2.0 @ 8x lane speed does not bottleneck a dual GPU setup to the point it can not push at least 60FPS at 3440-1440 resolution on my 34" 21/9 LG 34UM95 monitor their is no reason to upgrade whatsoever.

    Also with DX12's reduced CPU overhead any new DX12 games should run great with a old Sandy CPU. Also DX12 Should greatly improve the performance of my EVGA's GTX 770 4gb Classified SLI setup since it will split frame render instead of alternate frame rendering allowing the vram to be sorta stacked since each card is only rendering half a frame instead of a whole frame allowing the 4gb of Vram on each card to act like one 8GB card.
  • PrinceGaz - Monday, August 3, 2015 - link

    Skylake should be the big one that has been waited for since Sandy Bridge; Ivy Bridge's tick reduced overclockability because of the process node, Haswell improved IPC but added the onboard voltage regulator which made overclocking at that node still worse, and Broadwell keeps the voltage regulator whilst further focussing on lower power.

    I'm not saying Skylake will go to the dizzying raw gigahertz of Sandy Bridge, but two generations of tocks, and the removal of the onboard voltage regulator, and if we're lucky, the improved thermal compound used in Haswell Devil's Canyon, could together make for a significantly faster chip; one which may well see the upper ends of the 4.x GHz attainable.
  • Impulses - Monday, August 3, 2015 - link

    Fingers crossed, if it can come near SB levels of OC I'd be complacent... Just enough for the IPC advantage not to be mitigated by raw clock speed, I'm really upgrading my 2500K for the platform anyway (M.2 in particular) but it'd be nice to get a halfway decent CPU upgrade. Reply
  • Aspiring Techie - Monday, August 3, 2015 - link

    The Broadwell equivalent of a Sandy Bridge 5.0 GHz overclock in raw instruction throughput (assuming that Skylake doesn't have any improvement in ipc) is 4.3 GHz. A 4.6 GHz Haswell overclock is equivalent to a 4.4 GHz Broadwell. Broadwell wasn't designed for the desktop, so it isn't designed for good overclocking. If Skylake's consumer flagship has the same clocks as the 4790K with say 10% ipc over Broadwell, then at 4.4 GHz, it has will have the same instruction throughput as a 5.0 GHz Haswell or a 5.7 GHz Sandy Bridge chip. The overclock should increase as the 14nm process becomes more mature, so less voltage is needed for better clocks. If Intel does it right, then everyone will be happy (except AMD since Zen would be screwed over). Reply

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