Intel’s Tiger Lake 11th Gen Core i7-1185G7 Review and Deep Dive: Baskin’ for the Exotic
by Dr. Ian Cutress & Andrei Frumusanu on September 17, 2020 9:35 AM EST- Posted in
- CPUs
- Intel
- 10nm
- Tiger Lake
- Xe-LP
- Willow Cove
- SuperFin
- 11th Gen
- i7-1185G7
- Tiger King
New Instructions and Updated Security
When a new generation of processors is launched, alongside the physical design and layout changes made, this is usually the opportunity to also optimize instruction flow, increase throughput, and enhance security.
Core Instructions
When Intel first stated to us in our briefings that by-and-large, aside from the caches, the new core was identical to the previous generation, we were somewhat confused. Normally we see something like a common math function get sped up in the ALUs, but no – the only additional changes made were for security.
As part of our normal benchmark tests, we do a full instruction sweep, covering throughput and latency for all (known) supported instructions inside each of the major x86 extensions. We did find some minor enhancements within Willow Cove.
- CLD/STD - Clearing and setting the data direction flag - Latency is reduced from 5 to 4 clocks
- REP STOS* - Repeated String Stores - Increased throughput from 53 to 62 bytes per clock
- CMPXCHG16B - compare and exchange bytes - latency reduced from 17 clocks to 16 clocks
- LFENCE - serializes load instructions - throughput up from 5/cycle to 8/cycle
There were two regressions:
- REP MOVS* - Repeated Data String Moves - Decreased throughput from 101 to 93 bytes per clock
- SHA256MSG1 - SHA256 message scheduling - throughput down from 5/cycle to 4/cycle
It is worth noting that Willow Cove, while supporting SHA instructions, does not have any form of hardware-based SHA acceleration. By comparison, Intel’s lower-power Tremont Atom core does have SHA acceleration, as does AMD’s Zen 2 cores, and even VIA’s cores and VIA’s Zhaoxin joint venture cores. I’ve asked Intel exactly why the Cove cores don’t have hardware-based SHA acceleration (either due to current performance being sufficient, or timing, or power, or die area), but have yet to receive an answer.
From a pure x86 instruction performance standpoint, Intel is correct in that there aren’t many changes here. By comparison, the jump from Skylake to Cannon Lake was bigger than this.
Security and CET
On the security side, Willow Cove will now enable Control-Flow Enforcement Technology (CET) to protect against a new type of attack. In this attack, the methodology takes advantage of control transfer instructions, such as returns, calls and jumps, to divert the instruction stream to undesired code.
CET is the combination of two technologies: Shadow Stacks (SS) and Indirect Branch Tracking (IBT).
For returns, the Shadow Stack creates a second stack elsewhere in memory, through the use of a shadow stack pointer register, with a list of return addresses with page tracking - if the return address on the stack is called and not matched with the return address expected in the shadow stack, the attack will be caught. Shadow stacks are implemented without code changes, however additional management in the event of an attack will need to be programmed for.
New instructions are added for shadow stack page management:
- INCSSP: increment shadow stack pointer (i.e. to unwind shadow stack)
- RDSSP: read shadow stack pointer into general purpose register
- SAVEPREVSSP/RSTORSSP: save/restore shadow stack (i.e. thread switching)
- WRSS: Write to Shadow Stack
- WRUSS: Write to User Shadow Stack
- SETSSBSY: Set Shadow Stack Busy Flag to 1
- CLRSSBSY: Clear Shadow Stack Busy Flag to 0
Indirect Branch Tracking is added to defend against equivalent misdirected jump/call targets, but requires software to be built with new instructions:
- ENDBR32/ENDBR64: Terminate an indirect branch in 32-bit/64-bit mode
Full details about Intel’s CET can be found in Intel’s CET Specification.
At the time of presentation, we were under the impression that CET would be available for all of Intel’s processors. However we have since learned that Intel’s CET will require a vPro enabled processor as well as operating system support for Hardware-Enforced Stack Protection. This is currently available on Windows 10’s Insider Previews. I am unsure about Linux support at this time.
Update: Intel has reached out to say that their text implying that CET was vPro only was badly worded. What it was meant to say was 'All CPUs support CET, however vPro also provides additional security such as Intel Hardware Shield'.
AI Acceleration: AVX-512, Xe-LP, and GNA2.0
One of the big changes for Ice Lake last time around was the inclusion of an AVX-512 on every core, which enabled vector acceleration for a variety of code paths. Tiger Lake retains Intel’s AVX-512 instruction unit, with support for the VNNI instructions introduced with Ice Lake.
It is easy to argue that since AVX-512 has been around for a number of years, particularly in the server space, we haven’t yet seen it propagate into the consumer ecosphere in any large way – most efforts for AVX-512 have been primarily by software companies in close collaboration with Intel, taking advantage of Intel’s own vector gurus and ninja programmers. Out of the 19-20 or so software tools that Intel likes to promote as being AI accelerated, only a handful focus on the AVX-512 unit, and some of those tools are within the same software title (e.g. Adobe CC).
There has been a famous ruckus recently with the Linux creator Linus Torvalds suggesting that ‘AVX-512 should die a painful death’, citing that AVX-512, due to the compute density it provides, reduces the frequency of the core as well as removes die area and power budget from the rest of the processor that could be spent on better things. Intel stands by its decision to migrate AVX-512 across to its mobile processors, stating that its key customers are accustomed to seeing instructions supported across its processor portfolio from Server to Mobile. Intel implied that AVX-512 has been a win in its HPC business, but it will take time for the consumer platform to leverage the benefits. Some of the biggest uses so far for consumer AVX-512 acceleration have been for specific functions in Adobe Creative Cloud, or AI image upscaling with Topaz.
Intel has enabled new AI instruction functionality in Tiger Lake, such as DP4a, which is an Xe-LP addition. Tiger Lake also sports an updated Gaussian Neural Accelerator 2.0, which Intel states can offer 1 Giga-OP of inference within one milliwatt of power – up to 38 Giga-Ops at 38 mW. The GNA is mostly used for natural language processing, or wake words. In order to enable AI acceleration through the AVX-512 units, the Xe-LP graphics, and the GNA, Tiger Lake supports Intel’s latest DL Boost package and the upcoming OneAPI toolkit.
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AMDSuperFan - Monday, September 21, 2020 - link
What really concerns me is this Intel Tiger is built on a 10mm process that looks like it is as good or better than the TSMC 7nm process. https://en.wikipedia.org/wiki/7_nm_process. They do not talk about the +++ superfin variants for node density. We need Super Navi to fight against this. We know for laptops or gaming, nobody can touch big navi. Nvidia cannot. It will be much faster I think than 3090 or even 4090 by everything I see. Nvidia might be out of their league finally and put into their place. I would not be surprised to see Big Navi designs at 150w with 10x the speed.Rtx dude - Monday, September 28, 2020 - link
3090 is twice the size of 3080. So, it will ebd big NAVI in performance and bebchmarksShowtime - Friday, September 18, 2020 - link
Sorry, but with your name alone, we can't take anything you say seriously.MrVibrato - Saturday, September 19, 2020 - link
Oh, but there are quite a few who couldn't resist the bait. Which, and this is one of my guilty pleasures, makes for entertaining reading...hecksagon - Friday, September 18, 2020 - link
He's referencing the performance improvement we will see in AMD's integrated graphics once the architectural improvements from Big Navi trickle down.dotjaz - Friday, September 18, 2020 - link
In the meantime, Intel wins for the next 8 months or so. We don't even know if Van Gogh can beat TGL yet.Spunjji - Friday, September 18, 2020 - link
That's a charitable interpretation, but actually this account is just a sockpuppet for an Intel shill who got tired of waiting for AMD fanboys to show up and so made one of their own. Everything they post is nonsensical junk.AMDSuperFan - Monday, September 21, 2020 - link
Even as a superfan it seems obvious that our amd cannot fight against this new technology. How is a usurper faster than us on video for gaming? As the owner of ATI, we are a video gaming company. Nvidia with their Voodoo 2 technology has nothing on ATI. My 7900 card is still fast for many games even today - but the same cannot be said for Voodoo 2 cards. But we have big things on the future and we should get back our championship in 2022.PixyMisa - Thursday, September 17, 2020 - link
This was almost funny once.SarahKerrigan - Thursday, September 17, 2020 - link
Big Navi is a multi-hundred-watt dGPU. This is a laptop processor. They don't compete with each other at all.