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Why is Core i7 920 better than Phenom 2 955

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May 17, 2009 11:46:19 AM

I just want to ask the question above...Core i7 clockspeed is lower, the amount of cache is the same but why does it performs better in most apps? I wonder how, I wonder why...

More about : core 920 phenom 955

May 17, 2009 1:15:59 PM

Core I7 architecture is different to Phenom II architecture,
The frecuency (clockspeed) is not the most important factor anymore... Some differences:

I7 has more L3 Cache,
HT technology (which allows it to become an "" 8-Cores-CPU """ ),
A better memory controller system (Tri-Channel and up to 2000Mhz vs. Dual-Channel and up to 1600Mhz... right?),

By the way, there`s not a huge difference... It deppends on the software you use, on High-Res gaming they run very similar... But I7 is better in many other things.
May 17, 2009 2:16:35 PM

and it has a slightly higher IPC (instructions per clock)
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a b à CPUs
May 17, 2009 2:21:30 PM

I think it is mainly due to Intel's superior cache and prefetch design, and, given the core2 cores have higher IPC than K8's then all things now equal ... both now have an IMC ... then the i7 is slightly faster on most applications than K10.5.

i7 and K10.5 both have cores that are essentially based on their predecessors.

a b à CPUs
May 17, 2009 2:31:28 PM

You don't throw away 10 years worth of effort sorting bugs out of a core unless the previous model was better ... its very hard to start from scratch.

That's why they threw the Pentium 4 away and reworked the Pentium 3 (mobile) to come up with core2. P3 had a higher IPC than P4 ... the pipes were a better design ... or could be improved moreso. The core2 cores are at the heart of the i7 ... some changes of course.

Sorry for the oversimplification ... very crude explanation.
May 17, 2009 2:40:48 PM

In my opinion the Phenom II is still better value for money and fast enough for most. The Average user isn't going to really see a difference. Oh yeah Hyperthreading is a Gimmick, it still only has four processor cores.
a b à CPUs
May 17, 2009 2:47:34 PM

I agree ... for the price it is hard to go past.

But it isn't a better CPU.
a c 83 à CPUs
May 17, 2009 3:21:39 PM

speedbird said:
In my opinion the Phenom II is still better value for money and fast enough for most. The Average user isn't going to really see a difference. Oh yeah Hyperthreading is a Gimmick, it still only has four processor cores.


I'll agree since you can find Newegg combos and pick up a Phenom II 940, 4Gb (2x2) DDR2 1066, and a AM2+ motherboard for less than the I7 920 costs alone. Although AMD is going to be in trouble when the I5 is released.
May 17, 2009 4:35:58 PM

phenom II is better value until the i7 price cuts come, and i5 will be just a bit cheaper than i7 is now so AMD doesn't really need to be worried.

I think Intel is making a mistake though by using larrabee as a GPU, if they used it as a CPU they would easily own the market but then I guess the EU would stomp down on them for taking out the competition.
May 17, 2009 4:48:02 PM

thanks guys... So the i7 does better work per clockspeed but not better work per dollar?

Actually I'm gonna build a desktop in quarter three, so this helps me although i don't really understand what some of guys are saying. lol

My plan is:

MSI GD-70
Phenom II 955
2GB Corsair DDR3 1333 DHX
Corsair TX 650
2 X ATI Radeon 4770
Cooler Master CM 690

Are these things suitable?
And good value for money?

I just want to play games a lot because I have restrained my self from doing so for three or four years
a c 126 à CPUs
May 18, 2009 1:43:50 AM

Reynod said:
You don't throw away 10 years worth of effort sorting bugs out of a core unless the previous model was better ... its very hard to start from scratch.

That's why they threw the Pentium 4 away and reworked the Pentium 3 (mobile) to come up with core2. P3 had a higher IPC than P4 ... the pipes were a better design ... or could be improved moreso. The core2 cores are at the heart of the i7 ... some changes of course.

Sorry for the oversimplification ... very crude explanation.


While this is close, its a bit off. Core 2 is actually based off of the Pentium III Coppermine that was a desktop part. What happened was that during the Pentium 4 era is that Intel needed a good mobile offense against AMDs Athlon that was low power and decent performance.

What they did is they wrapped the Pentium III Coppermineinto a mobile package naming it the Pentium M.

What they saw (well the guys in Israel anyways) was that it would run better than a Pentium 4 and clock per clock it whomped it and Athlon like there was no tomorrow.

So they took what they learned from Pentium 4 (lets faces it, the P4s pipeline design was better since it gave the ability to clock higher than others it was just the rest of the arch that had leakage up the arse) and applied it to the Pentium M thus creating Core 2.

Core i7 is Core 2 with a lot of IPC enhancements, a IMC and QPI.

speedbird said:
In my opinion the Phenom II is still better value for money and fast enough for most. The Average user isn't going to really see a difference. Oh yeah Hyperthreading is a Gimmick, it still only has four processor cores.


Its not HT. And it was a gimmick but SMT actually does give a nice performance boost. But yes the average user wont see any difference which is why a Pentium Dual Core E2200 is suffice for most average users.

Helloworld_98 said:
phenom II is better value until the i7 price cuts come, and i5 will be just a bit cheaper than i7 is now so AMD doesn't really need to be worried.

I think Intel is making a mistake though by using larrabee as a GPU, if they used it as a CPU they would easily own the market but then I guess the EU would stomp down on them for taking out the competition.


Well that depends on the Core i5s performance. It may be something AMD might worry about.

And Larrabee is a bit different. The design of the processors for it re mainly for GPU applications. Of course they could be using their design based off of Terascale mixed with Core i7s SMT (I think its supposed to be 32 processors with 64 threads and each core is capable of so many shaders) which will be great since Terascale was completely modular.

That means they could have some of the processors be PPUs(Physic Processing Units) and link it with Havoks Physics engine since they now own havok.

And you are right. If they released a CPU like Terascale or Larrabee they would end up monopolizing the market and especially the server market. Terascale was shwon to be able to do the same job as 130 CPUs (it was only 80) and only used 62w @ full load @ 2.5GHz per core. And we all know Intel doesn't want that to happen or they will be broken up again which in the end is bad for us end users.

q_nanotubes said:
thanks guys... So the i7 does better work per clockspeed but not better work per dollar?

Actually I'm gonna build a desktop in quarter three, so this helps me although i don't really understand what some of guys are saying. lol

My plan is:

MSI GD-70
Phenom II 955
2GB Corsair DDR3 1333 DHX
Corsair TX 650
2 X ATI Radeon 4770
Cooler Master CM 690

Are these things suitable?
And good value for money?

I just want to play games a lot because I have restrained my self from doing so for three or four years



Well what do you plan on doing? For gaming thats a pretty decent rig right there although for me I would go with the HD4870 2GB but thats cuz I am crazy.

Also, do you know what OS you plan to use? If its XP 2GB of RAM is fine but if its Vista or even Windows 7 4GB+ is always better.
a b à CPUs
May 18, 2009 3:36:29 AM

You can't compare Hyperthreading from the P4 era to now. If it made no difference, why does both performance and power consumption increase when it is enabled?
a b à CPUs
May 18, 2009 9:03:12 AM

jimmy did you not restate what I said?

Where was I off?



May 18, 2009 9:15:05 AM

@Psycho, show me some results with them all running at 1600mhz FSB/HT/QPI and 3.2ghz clock speed.

otherwise it will not be a fair test.
May 18, 2009 10:35:38 AM

Helloworld_98....you really don't get the point, do you? Psycho showed you exactly that HT makes a difference. Look when HT is OFF and when is ON on the same processor and you can see the difference.
May 18, 2009 10:43:32 AM

The fair test is the price test so you should compare 2 processors with the same or similar price.
May 18, 2009 11:42:07 AM

^ Yes but he also uses that same graph in situations where my point has more meaning.

And the extra bandwidth gives HT it's performance boost, drop the QPI down to 1600mhz and in theory there will be less difference between the i7 with HT and the Phenom II.
a b à CPUs
May 18, 2009 12:38:46 PM

Drop the clock speed and slow it down. No kidding?
a c 108 à CPUs
May 18, 2009 1:24:29 PM

q_nanotubes said:
thanks guys... So the i7 does better work per clockspeed but not better work per dollar?

Actually I'm gonna build a desktop in quarter three, so this helps me although i don't really understand what some of guys are saying. lol

My plan is:

MSI GD-70
Phenom II 955
2GB Corsair DDR3 1333 DHX
Corsair TX 650
2 X ATI Radeon 4770
Cooler Master CM 690

Are these things suitable?
And good value for money?

I just want to play games a lot because I have restrained my self from doing so for three or four years


Asus 790FX AM3 / PhII 720BE: $320
http://www.newegg.com/Product/ComboDealDetails.aspx?Ite...

Anandtech: Phenom II X3 720BE & CrossFire X Performance
http://www.anandtech.com/mb/showdoc.aspx?i=3533&p=9


Need OS and gaming resolution to tighten things up ...
May 18, 2009 2:18:10 PM

randomizer said:
Drop the clock speed and slow it down. No kidding?


I'm guessing this was aimed at me but until we fair out the playing field on the CPU's we won't actually know which one is faster clock for clock.
May 18, 2009 2:31:55 PM

You want to compare apples with pears. You can't. The only thing that we care of is the performance. Real tests and the price that we are paying. It is the same thing when AMD had lower speed processor (Athlon 64) compare to Intel (Pentium 4 and D) but still were much better than Intel. In the end doesn't matter how big is the FSB, core speed, cache memory,etc. Is important how much processing power can provide.
May 18, 2009 8:06:03 PM

^ well lowering the QPI multiplier would be a start.
a b à CPUs
May 19, 2009 12:11:13 AM

How is it fair to slow it down? I don't see the logic. Unless you slow the HyperTransport bus speed as well, then it's fair, because both are being restricted. Restricting one and not the other is not fair. By similar logic you could say "let's disable some of i7's cores and then it will compete evenly with Phenom II" :heink: 
a c 126 à CPUs
May 19, 2009 6:07:03 AM

Helloworld_98 said:
I'm guessing this was aimed at me but until we fair out the playing field on the CPU's we won't actually know which one is faster clock for clock.


I agree with Random. Why would you lower the CPUs QPI and not the HTT? Do you not like seeing a lower speed CPU beat the pants off of a higher clocked CPU? It happens all the time (Athlon X2 vs Pentium D?)

Using your logic as well, we should lower Phenom and Phenom IIs HTT to match that of the FSB of a C2Q for a FAIR and EVEN comparison when looking at that.

And rey, you said it was mainly based off a mobile part. It wasn't. It was based off of the roots of the Pentium III (desktop). And the P4 had a much better pipeline arch it was just much longer. Intel took the pipeline abilities of P4, shortened the pipes and made a lot of enhancements to the IPC, cache and such based off of Pentium III.

Every process gen is in Core 2/Core i7 somehow. Just like I am sure every gen (K6/K6-II/K7/K8) is somewhere in Phenom II.
May 19, 2009 9:05:56 AM

DMilardovich said:
I7 has more L3 Cache


Actually i7 has less cache compared to Phenom II. Phenom uses exclusive cache, i7 are using inclusive cache. Inclusive cache duplicates data in different cache levels. Exclusive cache don't do that.

http://en.wikipedia.org/wiki/CPU_cache#Exclusive_versus...
a b à CPUs
May 19, 2009 10:45:22 AM

Just stay away from them PCChips cache chips they used to put on the old 486's.

The legs weren't even connected ... now that's exclusive !!
May 19, 2009 6:04:17 PM

hyperthreading is not a gimmick dork! Read up on hyperthreading before you call it a gimmick. Ok, let's make it fair, Hypertransport is a gimmick.
a b à CPUs
May 19, 2009 11:17:25 PM

kassler said:
Actually i7 has less cache compared to Phenom II. Phenom uses exclusive cache, i7 are using inclusive cache. Inclusive cache duplicates data in different cache levels. Exclusive cache don't do that.

http://en.wikipedia.org/wiki/CPU_cache#Exclusive_versus...


The problem with exclusive caches is that the hypertransport bandwidth has to be used for snooping in the other cores' caches. See HERE :

Quote:
Nehalem’s 8MB and 16 way associative L3 cache is inclusive of all lower levels of the cache hierarchy and shared between all four cores. Although Intel has not discussed the physical design of Nehalem at all, it appears that the L3 cache sits on a separate power plane than the cores and operates at an independent frequency. This makes sense from both a power saving and a reliability perspective, since large caches are more susceptible to soft errors at low voltage. As a result, the load to use latency for Nehalem varies depending on the relative frequency and phase alignment of the cores and the L3 itself and the latency of arbitration for access to the L3. In the best case, i.e. phase aligned operation and frequencies that differ by an integer multiple, Nehalem’s L3 load to use latency is somewhere in the range of 30-40 cycles according to Intel architects. The advantage of an inclusive cache is that it can handle almost all coherency traffic without disturbing the private caches for each individual-core. If a cache access misses in the L3, it cannot be present in any of the L2 or L1 caches of the cores. On the other hand, Nehalem’s L3 also acts like a snoop filter for cache hits. Each cache line in the L3 contains four “core valid” bits denoting which cores may have a copy of that line in their private caches. If a “core valid” bit is set to 0, then that core cannot possibly have a copy of the cache line – while a “core valid” bit set to 1 indicates it is possible (but not guaranteed) that the core in question could have a private copy of the line. Since Nehalem uses the MESIF cache coherency protocol, as discussed previously, if two cores have valid bits, then the cache line is guaranteed to be clean (i.e. not modified). The combination of these two techniques lets the L3 cache insulate each of the cores from as much coherency traffic as possible, leaving more bandwidth available for actual data in the caches.

May 20, 2009 6:13:31 AM

kassler said:
Actually i7 has less cache compared to Phenom II. Phenom uses exclusive cache, i7 are using inclusive cache. Inclusive cache duplicates data in different cache levels. Exclusive cache don't do that.

http://en.wikipedia.org/wiki/CPU_cache#Exclusive_versus...


On the other hand, due to inclusive technique, Core i7 also has less cache miss than Phenom II (theoretically speaking). High rate of cache miss means in the case core cannot find the file in its L1 data, it will then seek data in L2, L2s in other cores, and L3s (also segmented among cores), before finally hitting the RAM. This causes outrageously high latencies.
a b à CPUs
May 20, 2009 6:26:17 AM

Core i7 latency is waaay higher than PhII.

PhII's cache is slower than the Core series CPUs too.
May 20, 2009 2:49:10 PM

Not really.

K10's latency:


Core i7's latency:


Not only that, the chance of Core i7 having a cache miss (which warrants a read from the RAM) is much lower than Phenom II due to inclusive cache.
a b à CPUs
May 20, 2009 3:16:59 PM

^ +1. Also note that for Istanbul, AMD is including a snoop filter that will look in the other 5 cores' caches for data before heading out to main memory, in an attempt to catch up to Intel. Of course, this will consume some of the hypertransport bandwidth.
May 20, 2009 3:26:49 PM

does that chart apply to the 955 too?
a c 126 à CPUs
May 21, 2009 7:51:55 AM

noodle64 said:
does that chart apply to the 955 too?


I don't see why not. The 955 is just a Phenom II 940 @ 3.2GHz. The actual chip itself is pretty much unchanged just mainly the clock speed.
a b à CPUs
May 22, 2009 7:57:32 AM

Yeh, that and a higher HT speed.
May 24, 2009 2:23:15 AM

hey tomshardware didn't notify me about the replies to this thread....

yes I only want to play a lot and lot of games and I will be using Vista then will change to windows 7. Am planning to use a 22 inch monitor.

Thanks for the answers. Really appreciate them.
a c 108 à CPUs
May 24, 2009 6:01:49 PM

q_nanotubes said:
hey tomshardware didn't notify me about the replies to this thread....

yes I only want to play a lot and lot of games and I will be using Vista then will change to windows 7. Am planning to use a 22 inch monitor.

Thanks for the answers. Really appreciate them.


22-inch very likely equals 1680 x 1050, right? :??: 

2 x HD 4770s have looked really good at that rez - and I was surprised how well they have mostly performed at 19x12, too.

It's a tough call (but) if I were gonna spend $200 today I'd snag an HD 4890 1GB for $200 AR ---->>
http://www.newegg.com/Product/Product.aspx?Item=N82E168...

And later on this year when you want to reward yourself (and the price continues to drop) I'd snag another one (so you can play all the upcoming games really fast on that new 50-inch 1080p plasma you get for the holidays - LOL)

a b à CPUs
May 25, 2009 5:01:24 AM

blah, blah. tired of seeing these pics....
a b à CPUs
May 25, 2009 5:04:21 AM

At least we have a browser cache. Imagine if you had to download them every time? I'd hit my bandwidth cap in a matter of days.
a b à CPUs
May 25, 2009 5:10:18 AM

lmao, good one. Damn i understand being proud of my rig, and it does look nice, but why in every thread?
May 25, 2009 5:35:52 AM

....so is that your computer?
a b à CPUs
May 25, 2009 12:08:20 PM

I am not tired of seeing those pics.

Just stick another 4870 in the box soldier.

a b à CPUs
May 25, 2009 12:09:23 PM

Nice to see your quoting Scotty W there Yo ... he writes superior articles.
May 25, 2009 1:26:24 PM



Hes got speed stickers on the side panel helps overclock with the magic green AMD lighting meaning the overclocking gnomes are working hard.

Word, Playa.
a b à CPUs
May 25, 2009 1:39:16 PM

Don't forget the Mac keyboard.
a b à CPUs
May 25, 2009 2:13:32 PM

jealous poor peons without the cash to bling up your rig ... like me.
a b à CPUs
May 26, 2009 1:01:52 AM

I have the cash, I prefer to keep it.
a b à CPUs
May 26, 2009 2:26:53 AM

I still like how the "screenshots" were taken with a camera. Shows true class.
a b à CPUs
May 26, 2009 11:49:18 AM

^+1 lmao
a b à CPUs
May 26, 2009 12:04:41 PM

I am too embarrassed to put up a photo of my PC.

She is a bit fat and has stretch marks.

Is a real goer though ... only locks up very rarely.

I will love her to eventual bits.
!