The Sandy Bridge Preview
by Anand Lal Shimpi on August 27, 2010 2:38 PM ESTOverclocking Controversy
It wasn’t until the Pentium II that Intel started shipping multiplier locked CPUs. Before then you could set the multiplier on your CPU to anything that was supported by the line, and if you had a good chip and good enough cooling you just overclocked your processor. Intel’s policies changed once remarking, the process of relabeling and reselling a lower spec CPU as a higher one, started to take off.
While multipliers were locked, Intel left FSB overclocking open. That would be an end user or system integrator decision and not something that could be done when selling an individual CPU. However, ever since before the Pentium III Intel had aspirations of shipping fully locked CPUs. The power of the enthusiast community generally kept Intel from exploring such avenues, but we live in different times today.
Two things have changed Intel’s feelings on the topic. First and foremost is the advent of Turbo Boost. So long as Intel doesn’t artificially limit turbo modes, we now have the ability to run CPUs at whatever clock speed they can run at without exceeding thermal or current limits. We saw the first really exciting Turbo with Lynnfield, and Sandy Bridge is going to expand on that as well. On the flip side, Intel has used Turbo as a marketing differentiator between parts so there’s still a need to overclock.
The second major change within Intel is the willingness to directly address the enthusiast community with unlocked K-series SKUs. We saw this recently with the Core i7 875K and Core i5 655K parts that ship fully unlocked for the overclocking community.
The K-series SKUs, these will be more important with Sandy Bridge
With Sandy Bridge, Intel integrated the clock generator, usually present on the motherboard, onto the 6-series chipset die. While BCLK is adjustable on current Core iX processors, with Sandy Bridge it’s mostly locked at 100MHz. There will be some wiggle room as far as I can tell, but it’s not going to be much. Overclocking, as we know it, is dead.
Well, not exactly.
Intel makes three concessions.
First and foremost we have the K-series parts. These will be fully unlocked, supporting multipliers up to 57x. Sandy Bridge should have more attractive K SKUs than what we’ve seen to date. The Core i7 2600 and 2500 will both be available as a K-edition. The former should be priced around $562 and the latter at $205 if we go off of current pricing.
Secondly, some regular Sandy Bridge processors will have partially unlocked multipliers. The idea is that you take your highest turbo multiplier, add a few more bins on top of that, and that’ll be your maximum multiplier. It gives some overclocking headroom, but not limitless. Intel is still working out the details for how far you can go with these partially unlocked parts, but I’ve chimed in with my opinion and hopefully we’ll see something reasonable come from the company. I am hopeful that these partially unlocked parts will have enough multipliers available to make for decent overclocks.
Finally, if you focus on multiplier-only overclocking you lose the ability to increase memory bandwidth as you increase CPU clock speed. The faster your CPU, the more data it needs and thus the faster your memory subsystem needs to be in order to scale well. As a result, on P67 motherboards you’ll be able to adjust your memory ratios to support up to DDR3-2133.
Personally, I’d love nothing more than for everything to ship unlocked. The realities of Intel’s business apparently prevent that, so we’re left with something that could either be a non-issue or just horrible.
If the K-series parts are priced appropriately, which at first indication it seems they will be, then this will be a non-issue for a portion of the enthusiast market. You’ll pay the same amount for your Core i7 2500K as you would for a Core i5 750 and you’ll have the same overclocking potential.
Regardless of how they’re priced, what this is sure to hurt is the ability to buy a low end part like the Core i3 530 and overclock the crap out of it. What Intel decides to do with the available multiplier headroom on parts further down the stack is unknown at this point. If Intel wanted to, it could pick exciting parts at lower price points, give them a few more bins of overclocking headroom and compete in a more targeted way with AMD offerings at similar price points. A benevolent Intel would allow enough headroom as the parts can reliably hit with air cooling.
The potential for this to all go very wrong is there. I’m going to reserve final judgment until I get a better idea for what the Sandy Bridge family is going to look like.
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chizow - Saturday, August 28, 2010 - link
OK it seems as if you were referring to the PCIe lanes connected off the actual P67 chipset, not the native PCIe controller integrated into the CPU. I do recall the P55 chipset supporting PCIe 2.0 but limiting it to PCIe 1.0 bandwidth for interconnects like USB or SATA controllers.chizow - Saturday, August 28, 2010 - link
Overall it looks like Sandy Bridge is a disappointment. One really has to question why Intel has reversed their Tick Tock cadence this time around by launching their low-mid range parts and platform so soon on the heals of P55/Lynnfield/Clarkfield, but I guess it makes more sense in the light of the fact Intel delayed that platform's launch for nearly a year. I would be EXTREMELY disappointed if I bought a P55 board in the last year only to find out Intel is again requiring a platform/socket change for what appears to be a marginal upgrade.There's also some clear deficiencies and disappointments in terms of improvements over last-gen platforms with P67:
1) No additional L2/L3 cache, in some cases less than previous gen.
2) No native USB 3.0 support. One can conjure up myriad reasons for why Intel is resisting USB 3.0 adoption, but its clearly obvious at this point that they have been resisting it since its inception.
3) Limited SATA 6G support. 2/8 ports I believe, but still better than nothing I suppose.
4) No additional PCIe lanes or PCIe 3.0 support, but at least they're finally going to support their actual PCIe 2.0 rated specs?
5) Limited/reduced overclockability. Big mistake imo, Intel seems to be forgetting why AMD was the enthusiast's choice back in the early Athlon/P4 days.
That leaves us with the major improvements:
1) 5-15% improvement clock-for-clock and core-for-core compared to older Nehalem and Westmere architectures.
2) Lower TDP
3) 2x faster GPU that's still too slow for any meaningful gaming
Hopefully the high-end X58 replacement platform offers bigger improvements. There's also some question as to whether LGA2011 will be HPC/server only and an intermediary platform (LGA1355) is to replace LGA1366, however, early rumors show it will introduce or improve upon many of the deficiencies I listed with P67 and show us what Sandy Bridge is really capable of. Get rid of that extraneous, massive GPU on the high-end and replace it with more L3 and execution units and we'll see some bigger gains than the underwhelming 5-15% we see with this first version of Sandy Bridge.
seapeople - Saturday, August 28, 2010 - link
Remember, that 5-15% clock-for-clock increase includes turboboost functioning on the current processors, which generally ratchets up the clock speed even in heavily multithreaded loads. It looks like the IPC increase with Sandy Bridge is at least 20% here. I would consider that fairly significant considering that Intel is already on top of the market with no real competition, other than for AMD to sell its top-of-the-line CPU's for cheap.It's also weird to see people deride IGP improvements that double the performance of the previous version. These integrated graphics are sufficient for probably 85% of the market (pretty much everyone who doesn't need to play current high-end games). Basically, the majority of people will be getting a free $50 graphics card built in to their processor, which itself is giving you a 20-40% performance improvement over a similarly priced last-gen processor.
chizow - Saturday, August 28, 2010 - link
Yeah I actually factored Turbo Boost not working on Sandy Bridge, as otherwise it would probably be closer to 0-10% increase clock-for-clock. Anand pegs SB ~10% faster overall clock-for-clock in his conclusion with another 3-7% with Turbo.Also, tempering any excitement over that 10% IPC increase we have the very bad news about Intel limiting overclocking significantly, so for virtually anyone who already owns a P55/Lynnfield/Clarkfield combo anything but a "K" designated chip may actually be a downgrade as you won't be able to easily enable your own homebrewed "Turbo" any longer with most Sandy Bridge SKUs. I'd say the nearly guaranteed 30-40% OC you lose far outweighs the prospective 10-15% clock-for-clock gain you'd see with Sandy Bridge.
As for the IGP being sufficient or any great accomplishment with what Sandy Bridge brings...I'd disagree. Sure I guess its great news for Intel that SB is actually able to adequately accelerate 1080p, but its still far from replacing even mid-range parts from 2-3 generations ago. If Anand perhaps ran some benchmarks at resolutions and settings people actually used it might be more relevant but the fact of the matter is, ~80% of "gamers" are gaming at resolutions of 1280x1024 or higher according to Steam Survey: http://store.steampowered.com/hwsurvey/
My issue with the IGP is its going to take up significant die space, I estimate at least as much die area for the 2C IGP relative to the rest of the 4C CPU using Clarkdale as a guideline. For those who have no interest in an IGP or go with the P67 platform that doesn't even support it, that's a waste of die space that you're still absorbing and paying for.
I just find it amazingly ironic how times have changed where the CPU was once thought of as the "general purpose" ASIC and the GPU was the "fixed-function", inflexible ASIC. How times have changed. With Sandy Bridge, we now have the CPU, an on-die IGP, and now even talk of an integrated super-sekret hardware video transcoder! Roles have clearly reversed as the CPU becomes ever-increasingly segmented and specialized while the GPU continues to evolve toward general purpose flexibility.
In that sense, I really think AMD has the right approach with Fusion, as their ALU and FPUs will be shared on their Bulldozer and Bobcat designs rather than segregated and specialized like on Sandy Bridge with its single-purposed CPU cores and IGP EUs.
DanNeely - Sunday, August 29, 2010 - link
80% of steam users is not the same thing as 80% of total PC buyers, or even 80% of the total gamers (think facebook games, etc). Serious gamers are not, any more than overclockers, a core market for Intel or AMD's CPU divisions.chizow - Sunday, August 29, 2010 - link
Yes I'm well aware Steam users do not make up 100% of the total PC market, but I would say it is a fair representation of the kind of hardware and resolution actual gamers use. In those same browser-based games you're referring to, any existing IGP would have been adequate but that's clearly not the market Intel is trying to entice or the point of the comparison, buyers who would otherwise choose discrete GPUs.As you can see, most of these users are not using Intel IGPs (only 7%) because they are inadequate for actual gaming at the resolutions ~80% of them game at, 1280x1024 or higher, so benching a bunch of games at 1024x768 and trying to pass off this new IGP as adequate tells me nothing as its not indicative of real world applications.
Also, I'd take this a step further and argue the vast majority of those buying one of these new Sandy Bridge processors and systems would opt for a much higher resolution than even 1280x1024, as the most common desktop resolutions available for purchase today are going to be wide aspect 1680x1050, 1920x1080, and 1920x1200 displays. When's the last time you were able to buy an OEM build with a 1024x768 native display or even a 4:3 or 5:4 display for that matter?
If Intel and AT want to pass this IGP off as an HD gaming solution to rival discrete solutions, bench some resolutions and settings people would actually expect to game at.
tatertot - Sunday, August 29, 2010 - link
No, the 10% average outperformance in this review (see the conclusion) is against the i7 880 which has been allowed to turbo.Anand uses "clock-for-clock" to distinguish that part from the "same price replacement" the i5 760.
So it achieves 10% average outperformance against a part that runs ~20% faster on single-threaded loads, ~15% faster on 2 threads... down to a bin or so of turboing on fully-threaded loads.
That puts the clock/clock performance improvement at around 20%, and this is not including AVX / hardware transcoding.
chizow - Sunday, August 29, 2010 - link
Yes the i7 880 is the basis for the clock-for-clock comparisons to come to 10% increase, with Turbo on SB he expects another 3-7% increase which is again, in-line with my estimate of 5-15% instead of 0-10% gain, clock-for-clock with and without Turbo.From the conclusion verbatim:
"Sandy Bridge seems to offer a 10% increase in performance. Keep in mind that this analysis was done without a functional turbo mode, so the shipping Sandy Bridge CPUs should be even quicker. I'd estimate you can add another 3 - 7% to these numbers for the final chips."
In almost all of the benches in the test, you are going to be limited to 1 or 2 Turbo bins max which is why Anand limited his estimates to 3-7%, because all of the tests will be using more than 1 core. Under the same tests the benefits of Turbo for both Lynnfield and SB are going to be the same assuming the final Turbo bins and throttling is also the same. So if Lynnfield only gets 1 bin at 2+ cores then SB would only get the same benefit, which is where I'm sure Anand based his estimates (100/3100 and 200/3100).
Simply put, a 15% or even 20% clock-for-clock increase after 2 years from a new architecture is underwhelming imo, especially considering everything else they've left out, but I guess this is what we've come to expect and be thrilled about in a market dominated by Intel without any real competition. Sorry, I'm just less than impressed, especially given the artificial restrictions Intel plans to place on overclocking, further reducing any IPC benefits from SB compared to Lynnfield.
seapeople - Sunday, August 29, 2010 - link
If you throw out Netburst, which was a significant decrease in IPC from Pentium III, when have we had significantly greater than 20% IPC increase within 2 years for an architecture? I understand your other complaints (although I don't see what's wrong with just buying the K models, which all indications suggest won't be much more expensive), but what were you really expecting in IPC increases? 40%? 60%?chizow - Sunday, August 29, 2010 - link
Netburst was a reduction in IPC but a tripling of clockspeed compared to P3, but surely you aren't forgetting the incredible gains in IPC from Netburst to Yonah (Core) and Conroe (Core 2)?Conroe effectively increased performance 100% clock-for-clock from P4 (or 50% or so from Yonah), as it offered some 50% better performance at 50% lower clockspeeds compared to Netburst. While I certainly don't expect that kind of revolutionary product every 2-3 years, we're not even close to that kind of gain in the 4-5 years since Conroe was introduced with not even that much aggregrate difference from Conroe/Penryn/Nehalem/Westmere to SB. From Conroe to SB, clock for clock, we're maybe looking at 50% improvement?
That's 2 full Tick-Tock cycles signaling Moore's Law is clearly dead to Intel when it comes to performance, they only loosely follow its cadence in terms of refreshes, die sizes, transistor counts and fab processes. In order to achieve those kinds of gains, they had to redesign their CPU from nearly the ground-up to compete with AMD, which had the performance lead at the time. Intel clearly hasn't felt the need to improve or innovate signfificantly since then as AMD is essentially 2 generations behind still in performance, about on par with their Penryn offerings at this point.