I just build my new pc which is a q9450, 4 gb ddr2 800, BFG 8800GTS 512 so this will be out dated when nehalem comes out and how long will it be for nehalem to be needed for games since right now not a lot of many games use quad core cpus. Will nehalem be a good product for the main stream gamer?
For the first year or so nehalem will be ridiculously expensive and used mainly in servers. It will be a while before all games use quad core not to mention nehalem. You'll get a quite few years out of that Q9450 before you need to move onto nehalem.
Only the eight core version of Nehalem provides significant benifit over whats available now. We still are yet to see the 8 thread SMT on 4 cores provide real world significant advantages. I think by the time your Q9450 becomes outdated, you will be moving onto something post Nehalem.
From what I've read the Nehalem CPUs will be twice as fast per core at the same clock speed at certain apps but on average 30-80% faster at the same clock speed.
Where it will separate itself is its a true quad core allowing 2 quad core dies in a single chip. 8 physical cores with hyperthreading allowing the CPU to scale between 8 and 16 logical cores. More importantly the memory access will be considerably faster.
@Vertigon, the idea behind hyperthreading is that you can dynamically allow a single physical cores processing power between 2 threads however the operating system will see this as 2 logical cores because of how hyperthreading persents itself to the OS(doing this avoids the need to have multi core and multi thread per core code). So if the 'two cores' are only running 1 thread a core will get 100% while the other gets nothing which effectively allows it to scale between 1 and 2 logical cores per a physical core.
Vertigon, hyperthreading could put a 1000 on a single core but basically more 2 is not worth it. You see appart from partitioning the CPU threading a second trick....
Consider a Core 2 45nm, it can take 5 instructions per a cycle but if the instruction group has 6 instructions that means it needs 2 cycle or 10 instructions leaving 4 wasted. Hyperthreading can 'redirect' in simple terms to the second virtual core. This is how on certain programs hyperthreading can 'give' or rather save up to 30% of the available processing power on a 4 instructions per cycle processor.
More logical cores would lead to more overhead countering the speed gains besides you could just swap threads between cycles making the extra virtual cores uselss in any case.
Ok thanks. So in theory how many logical cores could we have per physical core? Where does hyperthreading taper off?
The old Hyperthreading wasn't more than a few registers, flags and instructions that could hold a certain processor stage. The number of threads possible per core should only be limited by the transistor count and, logically, by the efficiency of the additional threads - which i believe is not that great, otherwise intel would've increased them earlier.
Another problem that limits the amount of virtual threads is the inter-core communication since all processors need to know which processor is holding which thread in "storage". If i'm not mistaken Intel uses some hyperthreading related technology on Larrabee where 1 core can juggle 4 threads.
I think with the new memory controler the new HT tech will be a whole lot more efficient. Another big benefit are the huge L2 cache sizes. If they improved the old Hyperthreading, and i bet they have, it will be very interesting to see and compare a single core with two threads against a real dual core.
Slobogob I was refering to the Core 2 Extreme Edition's second generation hyperthreading which was a huge improvement over the P4 hyperthreading since the P4 only has 2 instructions per cycle (not much to save there so the management overhead would at times create a small performance lose) but the Core 2 EE hyperthreading had undergone some updates and had 4 instructions per a cycle to work with leaving far more to be saved.
Edit: With Nehelam, a single socket CPU with dual die would communicate via the L2 cache for cores on the same die (unbelievable bandwidth) or via the memory controller which is capable of 24gb/s per a die if I understand correctly. Bandwidth shouldn't be a problem.
Slobogob I was refering to the Core 2 Extreme Edition's second generation hyperthreading which was a huge improvement over the P4 hyperthreading since the P4 only has 2 instructions per cycle (not much to save there so the management overhead would at times create a small performance lose) but the Core 2 EE hyperthreading had undergone some updates and had 4 instructions per a cycle to work with leaving far more to be saved.
Edit: With Nehelam, a single socket CPU with dual die would communicate via the L2 cache for cores on the same die (unbelievable bandwidth) or via the memory controller which is capable of 24gb/s per a die if I understand correctly. Bandwidth shouldn't be a problem.
The bandwidth is amazing, thanks to the memory controller, but the bandwidth was not the real problem. Once a thread gets "stored" in a virtual core, another thread gets processed. Once the old one gets loaded up again, data has to be fetched from the memory. With a little luck the data is still in the L2 cache, but if not the processor has to access the memory - and that's slow. With the new interconnect the access gets sped up and the L2 is larger which should improve Hyperthreading even without improvements to the hyperthreading tech itself. This is one of the reasons AMD does not have Hyperthreading. They can do a lot of work per clock and they can switch more easily between threads. Instead of catching up with the memory controller, intel tries to jump one step ahead of that by re-introducing a new version of Hyperthreading. I'm quite eager to see it at work.
There's not enough evidence to confirm how Nehalem will perform, so take any wild claims as a pinch of salt. You can also guarantee that Intel are not going to let these new CPU's go like the Value prices we have now, it'll probably take sometime for them to become affordable enough for your average mainstream user. There's always going to be something better there's no such thing as 'Future proofing', always buy what's best for a given budget at the time, not worth waiting. Being Native Quad core does not always mean it's going to be better, AMD have had problems with theirs and Intel could well encounter problems too.
There's not enough evidence to confirm how Nehalem will perform, so take any wild claims as a pinch of salt. You can also guarantee that Intel are not going to let these new CPU's go like the Value prices we have now, it'll probably take sometime for them to become affordable enough for your average mainstream user. There's always going to be something better there's no such thing as 'Future proofing', always buy what's best for a given budget at the time, not worth waiting. Being Native Quad core does not always mean it's going to be better, AMD have had problems with theirs and Intel could well encounter problems too.
Wait for Official Benchmarks and testing
While i agree that official benchmarks are better than speculation, there are always indicators for what is to come. The totally botched launch of AMDs, on paper superior looking and by marketing gurus hyped up, Phenom, is a fine example. Everyone waiting for it will remember the hurricane of NDAs, mysterious and exclusive test-rigs and so on. I haven't heard or seen anything like that regarding intels latest.
