The Qualcomm Snapdragon 820 Performance Preview: Meet Kryo
by Ryan Smith & Andrei Frumusanu on December 10, 2015 11:00 AM EST- Posted in
- SoCs
- Snapdragon
- Qualcomm
- Snapdragon 820
CPU Performance: Meet Kryo
To dive right into the heart of matters then, after getting our standard benchmarks out of the way we had enough time left to load up some of our more advanced analysis tools to run on the 820 MDP/S. While Qualcomm has been somewhat forthcoming in the Kryo CPU architecture, they have never been as forward as say ARM (who is in the business of licensing the IP), so there are still some unanswered questions about what Kryo is like under the hood.
Qualcomm CPU Core Comparison | |||||||
Snapdragon 800 | Snapdragon 810 | Snapdragon 820 | |||||
CPU Codename | Krait | ARM Cortex-A57 | Kryo | ||||
ARM ISA | ARMv7-A (32-bit) | ARMv8-A (32/64-bit) | ARMv8-A (32/64-bit) | ||||
Integer Add | 1 | 2 | 1 | ||||
Integer Mul | 1 | 1 | 1 | ||||
Shifter ALUs | 1 | 2 | 1 | ||||
Addition (FP32) Latency | 3 cycles | 5 cycles | 3 cycles | ||||
Multiplication (FP32) Latency | 6 cycles | 5 cycles | 5 cycles | ||||
Addition (INT) Latency | 1.5 cycles | 1 cycle | 1 cycle | ||||
Multiplication (INT) Latency | 4 cycles | 3 cycles | 4 cycles | ||||
L1 Cache | 16KB I$ + 16KB D$ | 48KB I$ + 32KB D$ | 32KB I$ + 32KB D$? | ||||
L3 Cache | N/A | N/A | N/A |
One thing that immediately jumps out is how similar some of our results are to Krait. According to our initial tests, the number of integer and FP ALUs would appear to be unchanged. Similarly the latency for a lot of operations is similar as well. This isn’t wholly surprising as Krait was a solid architecture for Qualcomm, and there is a good chance they agreed and decided to use it as their starting point. At the same time however I do want to note that these are our initial results done rather quickly on what’s essentially a beta device; further poking later on may reveal more differences than what we’ve seen so far.
But with the above said, there’s a big difference between how many execution units a CPU design has and how well it can fill them, which is why even similar designs can have wildly different IPC. We’ll investigate this a bit more in a moment, however it’s worth noting that this is exactly the philosophy ARM has gone into with Cortex-A72, so it is neither unprecedented nor even unexpected.
Looking at the memory hierarchy and latency, our results point to a 32KB L1 data cache. For the moment I’m assuming the instruction cache is identical, as is the case on most designs, but this test is purely a data test. Meanwhile L2 cache size is a bit harder to pin down; we know that the different CPU clusters on 820 will be using different L2 cache sizes. Ultimately it's pretty much impossible to pin down the exact L2 cache size from this test alone, especially since we can't see the amount of L2 attached to the lower clocked Kryo cluster.
According to our colleague Matt Humrick over at Tom's Hardware, while investigating the matter, it seems that Qualcomm disclosed that we're looking at an 1MB L2 for the performance cluster and a 512KB L2 for the power cluster. We're still looking into independently confirming this bit of information with Qualcomm.
However what you won’t find – and much to our surprise – is an L3 cache. Our test results indicate (and Qualcomm confirms) that Snapdragon 820 does not have an L3 cache as we initially expected, with the L2 cache being the highest cache level on the chip. We initially reported there to be an L3 due to the fact that we found evidence and references to this cache block in Qualcomm's resources, but it seems the latest revision of the SoC doesn't actually employ such a piece in actual silicon, as demonstrated by the latency graph. This means that there isn’t any kind of cache back-stopping interactions between the two CPU clusters, or between the CPU and GPU. Only simple coherency, and then beyond that main memory.
Geekbench 3 Memory Bandwidth Comparison (1 thread) | ||||||
Stream Copy | Stream Scale | Stream Add | Stream Triad | |||
SD 801 (2458MHz) | 7.6 GB/s | 4.6 GB/s | 4.6 GB/s | 5.2 GB/s | ||
SD 810 (1958MHz) | 7.5 GB/s | 7.4 GB/s | 6.4 GB/s | 6.6GB/s | ||
SD 820 (2150MHz) | 17.4 GB/s | 11.5 GB/s | 13.1 GB/s | 12.8 GB/s | ||
SD 820 > 810 Advantage | 131% | 55% | 103% | 94% |
Meanwhile looking at Geekbench 3 memory performance, one can see that memory bandwidth is greatly improved over both Snapdragon 800/801 and 810. Stream copy in particular is through the roof, increasing by 131% (over double 810’s performance). Even the other tests, though not as great, are between 55% and 103%. The Snapdragon 820 also shows improved latency to main memory when compared to the Snapdragon 810, so it seems that Qualcomm made definite improvements in the memory controller and general memory architecture of the chipset, allowing the CPUs to get nearer to the theoretical total memory bandwidth offered by the memory controllers.
Moving on, let’s shift to some benchmarks that make a more comprehensive look at performance, starting with SPECint2000. Developed by the Standard Performance Evaluation Corporation, SPECint2000 is the integer component of their larger SPEC CPU2000 benchmark. Designed around the turn of the century, officially SPEC CPU2000 has been retired for PC processors, but with mobile processors roughly a decade behind their PC counterparts in performance, SPEC CPU2000 is currently a very good fit for the capabilities contemporary SoCs.
SPECint2000 - Estimated Scores | ||||||
Snapdragon 810 | Snapdragon 820 | % Advantage | ||||
164.gzip |
823
|
1176
|
43%
|
|||
175.vpr |
2456
|
1707
|
-30%
|
|||
176.gcc |
1341
|
1641
|
22%
|
|||
181.mcf |
789
|
593
|
-25%
|
|||
186.crafty |
1492
|
1449
|
-3%
|
|||
197.parser |
753
|
962
|
28%
|
|||
252.eon |
2321
|
3333
|
44%
|
|||
253.perlbmk |
1090
|
1384
|
27%
|
|||
254.gap |
1325
|
1447
|
9%
|
|||
255.vortex |
1043
|
1583
|
52%
|
|||
256.bzip2 |
867
|
1041
|
20%
|
|||
300.twolf |
DNC
|
DNC
|
N/A
|
Even though this early preview means we don’t have the luxury of building a binary with a compiler aware of Kryo, using our A57 binaries produces some preliminary results on the 820 MDP/S. Performance does regress in a couple of places – but in other places we see performance increases by up to 52%. 820 does have a slight 10% frequency advantage over 810, so when taking into account the clock difference the IPC improvements are slightly lower. This is also showcased when comparing the Snapdragon 820 to a more similarly clocked Exynos 7420 (A57 @ 2100MHz), where the maximum advantage drops to 33% and similarly to a clock-normalized Snapdragon 810, the overall average comes in at only 5-6%. Once we get the opportunity to have more time with a Snapdragon 820 device we'll be able to verify how much the compiler settings affect the score on the Kryo architecture.
Our other set of comparison benchmarks comes from Geekbench 3. Unlike SPECint2000, Geekbench 3 is a mix of integer and floating point workloads, so it will give us a second set of eyes on the integer results along with a take on floating point improvements.
Geekbench 3 - Integer Performance | ||||||
Snapdragon 810 | Snapdragon 820 | % Advantage | ||||
AES ST |
739.7 MB/s
|
700.7 MB/s
|
-5%
|
|||
AES MT |
3.05 GB/s
|
1.99 GB/s
|
-35%
|
|||
Twofish ST |
89.8 MB/s
|
102.7 MB/s
|
14%
|
|||
Twofish MT |
448.5 MB/s
|
345.5 MB/s
|
-23%
|
|||
SHA1 ST |
628.9 MB/s
|
983 MB/s
|
56%
|
|||
SHA1 MT |
3.02 GB/s
|
2.84 GB/s
|
-6%
|
|||
SHA2 ST |
83.5 MB/s
|
134.9 MB/s
|
61%
|
|||
SHA2 MT |
393.4 MB/s
|
374.6 MB/
|
-5%
|
|||
BZip2Comp ST |
5.01 MB/s
|
7.29 MB/s
|
45%
|
|||
BZip2Comp MT |
20.5 MB/s
|
20.5 MB/s
|
0%
|
|||
Bzip2Decomp ST |
7.99 MB/s
|
9.76 MB/s
|
24%
|
|||
Bzip2Decomp MT |
30.8 MB/s
|
24.9 MB/s
|
-19%
|
|||
JPG Comp ST |
18.9 MP/s
|
23.3 MP/s
|
23%
|
|||
JPG Comp MT |
88.9 MP/s
|
76.7 MP/s
|
-14%
|
|||
JPG Decomp ST |
41.5 MP/s
|
62.2 MP/s
|
49%
|
|||
JPG Decomp MT |
182.7 MP/s
|
176.6 MP/s
|
-3%
|
|||
PNG Comp ST |
1.11 MP/s
|
1.56 MP/s
|
43%
|
|||
PNG Comp MT |
4.78 MP/s
|
4.61 MP/s
|
-4%
|
|||
PNG Decomp ST |
17.9 MP/s
|
24.2 MP/s
|
35%
|
|||
PNG Decomp MT |
94.1 MP/s
|
64.3 MPs
|
-32%
|
|||
Sobel ST |
53.3 MP/s
|
86.3 MP/s
|
62%
|
|||
Sobel MT |
248.4 MP/s
|
244.8 MP/s
|
-1%
|
|||
Lua ST |
1.30 MB/s
|
1.59 MB/s
|
22%
|
|||
Lua MT |
5.93 MB/s
|
4.5 MB/s
|
-24%
|
|||
Dijkstra ST |
3.38 Mpairs/s
|
5.52 Mpairs/s
|
63%
|
|||
Dijkstra MT |
13.7 Mpairs/s
|
13.7 Mpairs/s
|
0%
|
The actual integer performance gains with GeekBench 3 are rather varied. Single-threaded results consistently show gains, ranging from a minor -5% regression for AES up to a 61% improvement for SHA2. Given the architecture shift involved here, this is a bit surprising (and in Qualcomm’s favor) since you wouldn’t necessarily expect Kryo to beat Cortex-A57 on everything. On the other hand MT results typically show a regression, since Snapdragon 810 had a 4+4 big.LITTLE configuration that meant that it had the 4 Cortex-A53 cores contributing to the task, along with the big cores all running at their near-full clockspeed, while Kryo’s second cluster runs at a reduced clockrate. And though one could have a spirited argument about whether single-threaded or multi-threaded performance is more important, I’m firmly on the side of ST for most use cases.
Geekbench 3 - Floating Point Performance | ||||||
Snapdragon 810 | Snapdragon 820 | % Advantage | ||||
BlackScholes ST |
5.46 Mnodes/s
|
12.3 Mnodes/s
|
125%
|
|||
BlackScholes MT |
25.5 Mnodes/s
|
32.1 Mnodes/s
|
26%
|
|||
Mandelbrot ST |
1.2 GFLOPS
|
2 GFLOPS
|
67%
|
|||
Mandelbrot MT |
6.41 GFLOPS
|
6.23 GFLOPS
|
-3%
|
|||
Sharpen Filter ST |
1.07 GFLOPS
|
2.15 GFLOPS
|
100%
|
|||
Sharpen Filter MT |
5.02 GFLOPS
|
6.11 GFLOPS
|
22%
|
|||
Blur Filter ST |
1.27 GFLOPS
|
3.14 GFLOPS
|
147%
|
|||
Blur Filter MT |
6.14 GFLOPS
|
8.84 GFLOPS
|
44%
|
|||
SGEMM ST |
2.29 GFLOPS
|
4.09 GFLOPS
|
79%
|
|||
SGEMM MT |
6.12 GFLOPS
|
9.19 GFLOPS
|
50%
|
|||
DGEMM ST |
1.05 GFLOPS
|
1.95 GFLOPS
|
85%
|
|||
DGEMM MT |
2.81 GFLOPS
|
4.53 GFLOPS
|
61%
|
|||
SFFT ST |
1.25 GFLOPS
|
1.98 GFLOPS
|
58%
|
|||
SFFT MT |
4.11 GFLOPS
|
5.65 GFLOPS
|
37%
|
|||
DFFT ST |
1.03 GFLOPS
|
1.68 GFLOPS
|
63%
|
|||
DFFT MT |
2.97 GFLOPS
|
4.76 GFLOPS
|
60%
|
|||
N-Body ST |
486.6 Kpairs/s
|
841 Kpairs/s
|
73%
|
|||
N-Body MT |
1.72 Mpairs/s
|
2.34 Mpairs/s
|
36%
|
|||
Ray Trace ST |
1.84MP/s
|
2.86 MP/s
|
55%
|
|||
Ray Trace MT |
8.16 MP/s
|
8.46 MP/s
|
4%
|
GeekBench 3’s floating point results are even more positive for Snapdragon 820. There is only a single performance regression, a -3% in Mandelbrot multi-threaded. Otherwise in both MT and ST workloads, performance is significantly up. This is a prime example of where Kryo is taking better advantage of its execution units than any high-end Qualcomm SoC before it, as even holding steady (or on paper having a slight deficit) it in practice comes out significantly ahead.
146 Comments
View All Comments
BurntMyBacon - Monday, December 14, 2015 - link
@mmrezaie: "It is actually at best as good as A72 performances reported so far, and not even on a same node size. So what was all the reason behind research and development when you build something as good as ARM's offering."To be fair, Qualcomm used ARM cores for the 810 and that turn out, lets say, less than stellar. I can understand why they might want to go back to their own IP. Even if performance is the same, that doesn't mean power consumption, heat density, etc. are the same. Samsung uses ARM cores for their Exynos chips and IIRC they had to fix a problem with their cores in the past as well to get the cores up to the speed they wanted. Also, designing it yourself can be cheaper than buying the core from ARM if you are proficient enough.
melgross - Thursday, December 10, 2015 - link
What happened, really, was that the Exynos chips weren't as good as the Snapdragon, and would be used in areas of the world where cost was more important that ultimate performance. The 810 wasn't used by them because it wasn't a very good chip, and it's only been recently, with the latter tape-outs, that aimed of the heating problems have been mitigated.lilmoe - Friday, December 11, 2015 - link
"Exynos chips weren't as good as the Snapdragon"I'm not sure when this false perception started, but that's just the fantasy of a handful of Snapdragon apologists. Exynos SoCs have ALWAYS been better than Snapdragons since their inception with the Hummingbird (GS1). Samsung has only stumbled with the Exynos 5410 (where they didn't have a "working" CCI), and less so on the 5420, and that was more like ARM's fault rather than Samsung's. Samsung later "fixed" ARM's design and moved forward with better chips than Qualcomm's offerings starting with the Exynos 5422 (except for the integrated modem part, up until recently that is).
They sometimes ran hotter than Snapdragons but Samsung always fixes things up with updates. Apps and Games have always run better and smoother on Exynos variants (even the 5410), and they've always aged better, *especially* after patches and software updates. I can attest to that through experience, and so can many reviewers.
Snapdragon apologists have always argued "custom ROM support". That's a very small percentage of users. Like REALLY small, to the point of irrelevance.
kspirit - Friday, December 11, 2015 - link
The main reason I do prefer devices with snapdragon SoCs is because of AOSP-based ROMs. You're right, it's a very small minority, but it's still nice to have. Samsung makes A+ hardware but their software is kind of meh to me. Personal preference and all.But Exynos hasn't historically been a very good chipset. Sure, it beat the 810 this year and did well with heat, but there have been shortcomings on Exynos in the past.
I remember back in the days of GS2, Exynos didn't have anything on their chipset to support notification LEDs (and even if they did, no one knew how to use them), while the same was available on Qualcomm's chips. Also, up to at least the Galaxy S4 (maybe even S5), Samsung's Exynos devices had a very seriously annoying lag between the time the home button was pressed and the screen turned on. Someone said it was because of the S-voice shortcut but it persisted on custom ROMs where S-Voice wasn't even there. It was some hardware thing.
TL;DR: being a benchmark destroyer isn't everything.
Andrei Frumusanu - Saturday, December 12, 2015 - link
Notification LEDs have absolutely nothing to so with the SoC...alex3run - Saturday, December 12, 2015 - link
Exynos 5410 wasn't really a failure just because its GPU is FAR ahead of Adreno 320 used in SD600. I was just surprised when saw how bad Adreno 320 runs real 3D games.LiverpoolFC5903 - Monday, December 14, 2015 - link
Thats nowhere near true I am afraid. The Powervr sgx 544 mp3 was beaten in almost every metric by the Adreno 320 rev.2. CPU wise the 5410 was better due to the use of higher ipc A15 cores but GPU performance was better in the Snapdragon 600, in real life as well as in most benchmarks.The Adreno 320 revision 2 is still relevant at around 85 Gflops, peforming better than midrangers like the Adreno 405 and Mali T760 MP2. Its almost identical in performance with the Rogue G6200 used in Mediatek's Mt6595 and Mt6795.
alex3run - Monday, December 21, 2015 - link
Sorry but Adreno 320 v2 doesn't exist at all. Stop believing the delusional lies from a chinese blog.As I said I was just surprised how bad Adreno 320 really is. I don't mind benchmarks because it seems like Qualcomm bought most benchmark makers. Only real performance I trust. Only in real games and apps.
tuxRoller - Monday, December 21, 2015 - link
How do you determine that the pvr sgx 544 is FAR ahead of the adreno 320?Anything reproducible?
V900 - Friday, December 11, 2015 - link
Actually Samsung probably wouldn't save any money by using an Exynos SOC.The two divisions are independent of each other, which means that Samsung the SOC vendor charges Samsung the device vendor the same prices they charge everyone else.
I doubt Apple would let them manufacture their CPUs if they weren't seperate divisions and had firewalls between them.