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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  • silverblue - Thursday, August 06, 2015 - link

    A "tweaked 8-core Ph2"? Putting aside the fact that significant changes would've been required to the fetch and retire hardware (the integer units themselves were very capable but were underutilised), a better IMC and all the modern instruction sets that K10 didn't support, AMD had already developed its replacement. It probably would've buried them to have to shelve Bulldozer (twice, it turns out) and redevelop what was essentially a 12-year old micro-architecture.

    AMD were under pressure to deliver Bulldozer hence the cutting of corners and the decision to go with GF's poor 32nm process as they simply didn't have any alternative (plus I imagine they were promised far more than GF could deliver). Phenom II was not enough against Nehalem, let alone Sandy Bridge.

    Blaming Intel doesn't help either as AMD couldn't exactly saturate the market with their products even when they were fabbing them themselves, however I think the huge drop in mainstream CPU prices when Core 2 was released along with the huge price paid for ATi did more damage than any bribing of retailers and systems manufacturers.
    Reply
  • nikaldro - Wednesday, August 05, 2015 - link

    40% over excavator, with 8 cores, good clockspeeds and good pricing doesn't sound that bad. I'll wait till Zen comes out, then decide. Reply
  • Spoelie - Thursday, August 06, 2015 - link

    IPC difference between piledriver and skylake amounts to 80%... Lets hope excavator's IPC is better than anticipated and 40% is sandbagging it a bit.

    Given AMD's track record of overpromising and underdelivering, I'm afraid Zen will massively disappoint.
    Reply
  • Asomething - Thursday, August 06, 2015 - link

    Well it will only be behind by something like 15-25% if the difference between piledriver and skylake is 80% since piledriver to excavator is supposed to be a good 20% jump. If amd can manage to catchup in any meaningful way and make chips that can touch 5ghz then things might turn out ok. Reply
  • mapesdhs - Thursday, August 06, 2015 - link

    Catchup will not be good enough. They need to be usefully competitive to pull people away from Intel into a platform switch, especially business, who have to think about this sort of thing for the long haul, and AMD's track record has been pretty woeful in this regard. I hope they can bring it to the table with Zen, but I'll believe it when I see it. Highly unlikely Intel isn't planning to either splat its prices or shove up performance, etc., if they need to when Zen comes out, especially for consumer CPUs. We know what's really possible based on how many cores, TDP, clock rates, etc. are used for the XEONs, but that potential just hasn't been put into a consumer chip yet.
    Remember, Intel could have released an 8-core for X79, but they didn't because there was no need; indeed the 3930K *is* an 8-core, just with 2 cores disabled (read the reviews). Ever since then, again and again, Intel has held back what it's perfectly capable of producing if it wanted to. The low clock of the 5960X is yet another example, it could easily be much higher.
    Reply
  • MapRef41N93W - Friday, August 07, 2015 - link

    You're assuming it's going to be a flat 40% over Excavator and not a best case scenario 40% (like every single AMD future performance projection always is...). It's more than likely a flat 20% IPC increase which puts it even behind Nehalem IPC wise.

    Top off the fact that it's AMD's first FinFET part (look at the penalty Intel paid in clockspeed with the transition to FinFET with IB/HW) and a transition to a new scalable uARCH (again look at the clockspeed hit Intel took when going from Netburst to scalable core arch, very similar to what AMD is doing now actually) and I can see Zen parts clocking horribly on top of that. Being on a Samsung node that is designed with low power in mind won't help their case either.

    You may get an 8 core Zen part for $300-$400 but it probably won't clock worth a damn and end up at 3.5-4GHz on average. So it would be a much worse choice than a 5820k for most people.
    Reply
  • mapesdhs - Wednesday, August 12, 2015 - link

    Btw, I wasn't assuming anything about Zen, I really haven't a clue how it'll compare to Intel's offerings of the day. I hope it's good, but with all that's happened before, I hope for the best but expect the worst, though I'd like to be wrong. Reply
  • Azix - Friday, August 21, 2015 - link

    You guys are being pretty negative on AMD. AMD tried to do an 8core chip on 32nm, maybe that was their mistake. The market wasn't even ready considering how long that way and where we are now. I do think intel got them pretty badly with their cheating

    The next processors are on a much better process. Based on the process alone we would expect a significant bit more performance than some seem willing to allow. Not to mention the original architecture was designed on a 32nm process. It's no surprise it would fall that far behind intel who is currently on 14nm. As time progresses though, those process jumps will take intel longer and longer. AMD will be much closer. Next year will be the first these two are on the same process (similar anyway). in a long while and it will last till at least 2017. AMD should be able to pick up some CPU sales next year and hopefully return to profitability. Intel also enjoys ddr4 support.

    Stop pushing old 32nm architectures and crappy motherboards.
    Reply
  • SkOrPn - Tuesday, December 13, 2016 - link

    Well if you were paying attention to AMD news today, maybe you partially got your answer finally. Jim Keller yet again to the rescue. Ryzen up and take note... AMD is back... Reply
  • CaedenV - Wednesday, August 05, 2015 - link

    Agreed, seems like the only way to get a real performance boost is to up the core count rather than waiting for dramatically more powerful single-core parts to hit the market. Reply

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