Comparing IPC on Skylake: Discrete Gaming

For this set of tests, we kept things simple – a low end single R7 240 DDR3, an ex-high end GTX 770 Lightning and a top line GTX 980 on our standard CPU game set under normal conditions. The IGP is not used here on the basis that each generation uses a substantially different integrated graphics arrangement.

Alien: Isolation

If first person survival mixed with horror is your sort of thing, then Alien: Isolation, based off of the Alien franchise, should be an interesting title. Developed by The Creative Assembly and released in October 2014, Alien: Isolation has won numerous awards from Game Of The Year to several top 10s/25s and Best Horror titles, ratcheting up over a million sales by February 2015. Alien: Isolation uses a custom built engine which includes dynamic sound effects and should be fully multi-core enabled.

For low end graphics, we test at 720p with Ultra settings, whereas for mid and high range graphics we bump this up to 1080p, taking the average frame rate as our marker with a scripted version of the built-in benchmark.

Alien Isolation on ASUS R7 240 DDR3 2GB ($70)

Alien Isolation on MSI GTX 770 Lightning 2GB ($245)

Alien Isolation on ASUS GTX 980 Strix 4GB ($560)

Total War: Attila

The Total War franchise moves on to Attila, another The Creative Assembly development, and is a stand-alone strategy title set in 395AD where the main story line lets the gamer take control of the leader of the Huns in order to conquer parts of the world. Graphically the game can render hundreds/thousands of units on screen at once, all with their individual actions and can put some of the big cards to task.

For low end graphics, we test at 720p with performance settings, recording the average frame rate. With mid and high range graphics, we test at 1080p with the quality setting. In both circumstances, unlimited video memory is enabled and the in-game scripted benchmark is used.

Total War: Attila on ASUS R7 240 DDR3 2GB ($70)

Total War: Attila on MSI GTX 770 Lightning 2GB ($245)

Total War: Attila on ASUS GTX 980 Strix 4GB ($560)

Grand Theft Auto V

The highly anticipated iteration of the Grand Theft Auto franchise finally hit the shelves on April 14th 2015, with both AMD and NVIDIA in tow to help optimize the title. GTA doesn’t provide graphical presets, but opens up the options to users and extends the boundaries by pushing even the hardest systems to the limit using Rockstar’s Advanced Game Engine. Whether the user is flying high in the mountains with long draw distances or dealing with assorted trash in the city, when cranked up to maximum it creates stunning visuals but hard work for both the CPU and the GPU.

For our test we have scripted a version of the in-game benchmark, relying only on the final part which combines a flight scene along with an in-city drive-by followed by a tanker explosion. For low end systems we test at 720p on the lowest settings, whereas mid and high end graphics play at 1080p with very high settings across the board. We record both the average frame rate and the percentage of frames under 60 FPS (16.6ms).

Grand Theft Auto V on ASUS R7 240 DDR3 2GB ($70)

Grand Theft Auto V on MSI GTX 770 Lightning 2GB ($245)

Grand Theft Auto V on ASUS GTX 980 Strix 4GB ($560)

GRID: Autosport

No graphics tests are complete without some input from Codemasters and the EGO engine, which means for this round of testing we point towards GRID: Autosport, the next iteration in the GRID and racing genre. As with our previous racing testing, each update to the engine aims to add in effects, reflections, detail and realism, with Codemasters making ‘authenticity’ a main focal point for this version.

GRID’s benchmark mode is very flexible, and as a result we created a test race using a shortened version of the Red Bull Ring with twelve cars doing two laps. The car is focus starts last and is quite fast, but usually finishes second or third. For low end graphics we test at 1080p medium settings, whereas mid and high end graphics get the full 1080p maximum. Both the average and minimum frame rates are recorded.

GRID: Autosport on ASUS R7 240 DDR3 2GB ($70)

GRID: Autosport on MSI GTX 770 Lightning 2GB ($245)

GRID: Autosport on ASUS GTX 980 Strix 4GB ($560)

Middle-Earth: Shadow of Mordor

The final title in our testing is another battle of system performance with the open world action-adventure title, Shadow of Mordor. Produced by Monolith using the LithTech Jupiter EX engine and numerous detail add-ons, SoM goes for detail and complexity to a large extent, despite having to be cut down from the original plans. The main story itself was written by the same writer as Red Dead Redemption, and it received Zero Punctuation’s Game of The Year in 2014.

For testing purposes, SoM gives a dynamic screen resolution setting, allowing us to render at high resolutions that are then scaled down to the monitor. As a result, we get several tests using the in-game benchmark. For low end graphics we examine at 720p with low settings, whereas mid and high end graphics get 1080p Ultra. The top graphics test is also redone at 3840x2160, also with Ultra settings, and we also test two cards at 4K where possible.

Shadow of Mordor on ASUS R7 240 DDR3 2GB ($70)

Shadow of Mordor on MSI GTX 770 Lightning 2GB ($245)

Shadow of Mordor on MSI GTX 770 Lightning 2GB ($245)

Shadow of Mordor on ASUS GTX 980 Strix 4GB ($560)

Shadow of Mordor on ASUS GTX 980 Strix 4GB ($560)

Conclusions on Gaming

There’s no easy way to write this.

Discrete graphics card performance decreases on Skylake over Haswell.

This doesn’t particularly make much sense at first glance. Here we have a processor with a higher IPC than Haswell but it performs worse in both DDR3 and DDR4 modes. The amount by which it performs worse is actually relatively minor, usually -3% with the odd benchmark (GRID on R7 240) going as low as -5%. Why does this happen at all?

So we passed our results on to Intel, as well as a few respected colleagues in the industry, all of whom were quite surprised. During a benchmark, the CPU performs tasks and directs memory transfers through the PCIe bus and vice versa. Technically, the CPU tasks should complete quicker due to the IPC and the improved threading topology, so that only leaves the PCIe to DRAM via CPU transfers.

Our best guess, until we get to IDF to analyze what has been changed or a direct explanation from Intel, is that part of the FIFO buffer arrangement between the CPU and PCIe might have changed with a hint of additional latency. That being said, a minor increase in PCIe overhead (or a decrease in latency/bandwidth) should be masked by the workload, so there might be something more fundamental at play, such as bus requests being accidentally duplicated or resent due to signal breakdown. There might also be a tertiary answer of an internal bus not running at full speed. To be sure, we rested some benchmarks on a different i7-6700K and a different motherboard, but saw the same effect. We’ll see how this plays out on the full-speed tests.

Comparing IPC on Skylake: Memory Latency and CPU Benchmarks Generational Tests on the i7-6700K: Legacy, Office and Web Benchmarks
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  • i_will_eat_you - Saturday, December 12, 2015 - link

    This is a good review, especially the look at memory latency. The 4690K is left out however from a lot of benchmarks. If you include that then I don't see much of an attraction to skylake. There is also the concern about the new rootkit support skylake introduces with protected code execution. This is not something I see being used for the good of the consumer.

    My one gripe is the lack of benchmarks for intense game engines (simulations, etc). Total war is there which is a step forward but I'm not sure if that benchmark really measures simulation engine performance.

    If you take games such as Sins of a Solar Empire or Supreme Commander then they have a separate thread for graphics so tend to maintain a decent frame rate even when the game engine runs at a crawl. The more units you add to the map and the more that is going on the slower it goes. But this is not in FPS. It means that ordering a ship across the solar system might take 10 s when there are 1000 units in the game but 5 minutes when there are 100000 units in the game. I would love to see some benchmarks measuring engine performance of games such as this with the unit limits greatly increased. It is a bit of a niche but many sim games (RTS, etc) scale naturally which means you can increase the unit limit, map size, AI difficulty, number of AIs, etc as your hardware becomes more powerful.

    This is especially relevant with CPUs such as the broadwell which might gain a big advantage each game loop processing the very large simulation engine dataset.
    Reply
  • systemBuilder - Tuesday, July 19, 2016 - link

    Wow your review really sucked. Where are the benchmarks for the i5-6600k? Did you forget? Reply
  • POPCORNS - Friday, August 19, 2016 - link

    To me, It doesn't matter if there's no IPC improvement over Sandy Bridge, Ivy Bridge or Haswell,
    Because I've upgraded from a Wolfdale Celeron (E3300) to a Skylake (6700K), lol.
    Reply
  • oranos - Thursday, December 29, 2016 - link

    This article seems to be confused. DDR4 brings more sustained framerates for higher resolutions (especially 4k). Really a waste of time doing a 1080p comparison. Reply
  • oranos - Thursday, December 29, 2016 - link

    if you wanted to do a proper test for DDR4 gaming performance you should run a 6700K and GTX 1080 minimum and run multiple games in 4K for testing. Reply

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