Nehalem Part 3: The Cache Debate, LGA-1156 and the 32nm Future
by Anand Lal Shimpi on November 19, 2008 8:00 PM EST- Posted in
- CPUs
What to Buy: Mainsteam vs. High End Nehalem
With two sockets targeted at desktops, how will the Core i7s that launched this month stack up to the mainstream Lynnfield and Havendale parts?
The absolute highest frequencies will only be available in LGA-1366 packages and I’d expect this is where we’d see 8-core/16-thread Nehalem parts first (if not exclusively). We’ve already shown that the three DDR3 channels don’t really help for most desktop applications, but this could change when Nehalem moves to 8 cores. Overclockability may also be better on LGA-1366 as the CPUs themselves will be higher bins.
Intel’s roadmaps show three pricepoints of Lynnfield processors in 2009. The top end Lynnfield part looks to be something that’s similar in price/frequency to the i7-940 (or whatever replaces it in Q3 2009). If I were to guess I’d say that’d be a $562 3GHz+ Lynnfield with performance somewhere in between an i7-940 and i7-965.
There will be a midrange Lynnfield, most likely priced/clocked similarly to the i7-920 or its eventual replacement. I’d guess a 2.66GHz - 2.93GHz CPU priced at around $284. Finally the low-end Lynnfield will be somewhere near $200 and probably weigh in at 2.4/2.53GHz. With Havendale not arriving until 2010, it’s currently absent from all Intel roadmaps.
Intel is going to support both platforms, LGA-1366 and LGA-1156 for the long term, the difference will be in the type of processors enabled. LGA-1366 may end up being more of a high end enthusiast play, Intel indicated that LGA-1366 CPUs would be binned higher so you can expect higher overclocks and obviously higher top end frequencies.
At the same time you should be able to get pretty far with LGA-1156, simple 500MHz overclocks shouldn’t be a problem but the 1GHz+ overclocks we’re used to on LGA-1366 and LGA-775 may not be as possible - at least not at 45nm.
Intel isn’t going to do anything to limit overclocking on LGA-1156 platforms, the same current limit bypass that’s on LGA-1366 boards will be optional on 1156 boards should the motherboard manufacturer choose to support it.
The breakdown seems pretty simple: if you’re the type of person who bought the Q6600/Q9300, then Lynnfield may be the Nehalem for you. If you spent a bit more on your CPU or are more of an enthusiast overclocker, the current Core i7 seems like the path Intel wants you to take.
The issue with Lynnfield is that it’s a good 6+ months away, and if Core i7 can speedup your workloads a lot today then you’ll be tempted to make the upgrade now. In notebooks we’ll see Lynnfield in the larger machines and Havendale in most of the platforms.
Without mainstream mobile Nehalem until Q1 2010, next year will be a very long wait for a serious mobile upgrade. But if you can wait it out, or buy something cheaper today, the time to upgrade will be in Q1 2010. I’m going to go ahead and revise my Apple notebook recommendation given that we probably won’t see a Nehalem based MacBook until 2010. Buy the cheapest MacBook you can today and make it last, upgrade again in 2010. Ooh, that rhymes.
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IntelUser2000 - Saturday, November 22, 2008 - link
To: ltcommanderdataActually you can't compare to Dothan. You have to compare to Conroe/Penryn. Conroe's L2 latency is at 14 cycles. I think it went up to make up for the complexity of the core(which is more than Dothan). Nehalem makes it even more complex.
The reason individual transistors can run at 200GHz+ within certain research labs but nowhere near with a commercial chip is they have to synchronize every part of the chip with the clock.
The CPU designers seem to take some chances when making a chip. Likely that's the reason for the delays for certain products as if you make a wrong decision then the prototypes might not come up as you wanted and you gotta make up for it.
That's probably the reason that Conroe didn't come with SMT as the Israeli team managing the chip wasn't experienced as the team that made the P4. They probably could have but risking it would not have been a good idea.
The Israeli team clings on proven technologies while the Hillsbro team makes up more radical ones, like Trace Cache, Out of Order, SMT, etc.
JonnyDough - Friday, November 21, 2008 - link
It should be exactly like Penryn. Die shrink = less heat = higher clocks = performance increase.ltcommanderdata - Friday, November 21, 2008 - link
The point is that Penryn was not just a dumb shrink of Conroe with added cache as Presler was of Smithfield. Penryn wasn't a major redesign, but it did have architectural tweaks over Conroe including speeding up how the execution units divide numbers and execute shuffles. The FSB was also reworked to allow half multipliers while lower power states were added in mobile versions. VT support was enhanced and of course SSE4.1 was added.I believe clock-for-clock Penryn is on average 5% faster than Conroe while the difference can be substantially higher for SSE4.1 optimized apps. When I say I hope Westmere is more like Penryn, I'm hoping for similar tweaks to be made to increase performance clock-for-clock, rather than just relying on 32nm to increase clock speeds. I don't believe Intel is releasing another SSE instruction set before AVX in Sandy Bridge, so I guess they'll have to dig deeper for a performance boost.
VaultDweller - Thursday, November 20, 2008 - link
"We’re finally getting wind of X58 motherboards at well below $300"Oh, please do share! This is what I'm interested in. Without this I would not even consider touching Nehalem with a ten foot pole.
In the past I brushed off X38 and X48 completely, as it was so hard to find reasonable motherboards based on these chipsets. X58 is shaping up to be the same.
The problem is that when I found X38 to be too expensive, I was able to find my peace with a P35 board (a P5K Premium). If I had building a system when X48 was hot off the press, I could find comfort knowing that P45 was right around the corner. There is no such comfort with Nehalem - the only lower-priced chip platform on the radar is based on a different socket, like S754 all over again.
I don't want to cripple or limit the options for my next system build by going with LGA1156, but I don't want to pay $300-450 for a motherboard either.
heavyglow - Thursday, November 20, 2008 - link
this is exactly what im thinking. im concerned that intel will abandon LGA1156 and ill be left with nothing.3DoubleD - Thursday, November 20, 2008 - link
I can think of the reverse scenario where AMD abandoned the 940 platform and released all FX processors on 939. Neither option is safe, just pick one you don't mind sticking with if you have to.Kiijibari - Thursday, November 20, 2008 - link
It's so small because Nehalem is a 100% Server design.Because of this Intel went ahead with the inclusive cache design. It comes in quite handy in MP systems, if you just have to probe one L3 only instead of 4 L1/L2 caches.
But there is one drawback, bigger L2 kills the benefit of the L3 size.
Neglecting the L1 Caches, Nehalem has an effective L3 size of 7 MB, as 4x256kb are just copied data from the L2.
Now imagine what would happen if intel would double the L2. Effective L3 cache size would have shrunk to 6MB, 2 MB waste .. that a lot of transistors.
To make L2 problems worse, Intel reintroduced Hyperthreading. Great technique, no doubt, but now we even have 2 threads struggling for the tiny, little 256kb cache.
I guess all the decisions pay off in a server environment, but to state that intel designed the small size L2 Caches because of the latency only is just a fine excuse for all the wanna-be gamers, who once heard that CL3 memory is better than CL5.
cheers
Kiiji
plonk420 - Thursday, November 20, 2008 - link
If 8core i7s will work on x58, i'll likely bite sooner rather than doing a "wait and see."does this seem highly likely? or is it anyone's guess?
Casper42 - Thursday, November 20, 2008 - link
Speaking of which, I ran across this today on accident:http://www.ecs.com.tw/ECSWebSite/Downloads/Product...">http://www.ecs.com.tw/ECSWebSite/Downlo...ilName=M...
The ECS X58B-A
Contains:
6 DDR3 Slots
2 x16 Slots
1 x4 Slot
2 x1 Slots
1 PCI Slot
The Manual makes mention of SLI as well which was surprising to me.
I can see that a machine with this ECS Board, a 920 proc and 2 x 9800GTX+ cards (Currently going for around $150 each) and you could have a pretty potent little machine for around $1000
iwodo - Thursday, November 20, 2008 - link
So we wont see new Mobile Part till 2010 ?That doesn't sound right to me at all. If that is the case then the rumours about it being a 32nm part may be right.
However, the idea Intel not updating their Mobile Part for 18 months doesn't sound right to me at all.