Any plans for dealing with dual cores?

Cooling Processors quietly

Moderators: NeilBlanchard, Ralf Hutter, sthayashi, Lawrence Lee

Post Reply
mathias
Posts: 2057
Joined: Sun Jul 11, 2004 3:58 pm
Location: Toronto
Contact:

Any plans for dealing with dual cores?

Post by mathias » Sun Sep 26, 2004 6:17 pm

If dual core CPU's will be almost twice as hot, does anyone have any plans for cooling that silently?

I don't see what makes dual cores any different from dual CPU's, so if dual cores cause multithreaded software to become widespread, I think I'll get a dual CPU system instead. This plan seems so obvious to me, there has to be something wrong with it, so what am I overlooking?

sthayashi
*Lifetime Patron*
Posts: 3214
Joined: Wed Nov 12, 2003 10:06 am
Location: Pittsburgh, PA

Post by sthayashi » Sun Sep 26, 2004 6:25 pm

If you've looked at the prices of dual processors lately, you'll see why that's not necessarily a cost effective solution for doing that. A dual Opteron system can cost close to $1000 for just the CPUs and Motherboard.
[size=75][url=http://www.twolf1300.net/sthayashi/SPCR/systems.html]My Power Rig, Storage Rig, HTPC and Main Rig[/url][/size]

mathias
Posts: 2057
Joined: Sun Jul 11, 2004 3:58 pm
Location: Toronto
Contact:

Post by mathias » Sun Sep 26, 2004 6:46 pm

I have sort of noticed that, though athlon64's in general seem rather expensive to me.

What about dual (mobile) XP's? AMD hasn't made tham unmoddable into MP's, have they?

sthayashi
*Lifetime Patron*
Posts: 3214
Joined: Wed Nov 12, 2003 10:06 am
Location: Pittsburgh, PA

Post by sthayashi » Sun Sep 26, 2004 7:00 pm

If you're handy with a scalpel and conductive paint, you can fake a normal XP into being an MP capable processor.

http://forums.2cpu.com/showthread.php?s=&threadid=29923

Really the 2cpu.com forums are the best forums for anything and everything dual processor related.

I have no idea how well mobile CPUs would work in a dual system. If you care to give me pair, I can find out for you... :D

To be honest though, I don't think dual core will necessarily mean twice the heat. I think it's more likely that they'll take their lower powered designs and dual core that, making the TDP about the same as other processors. But that's just pure speculation on my part.
[size=75][url=http://www.twolf1300.net/sthayashi/SPCR/systems.html]My Power Rig, Storage Rig, HTPC and Main Rig[/url][/size]

pony-tail
Posts: 488
Joined: Sat Aug 23, 2003 4:39 pm
Location: Brisbane AU

Post by pony-tail » Tue Sep 28, 2004 11:29 pm

From my understanding of Intels implementation of Dual core CPUs They will share the Cache and some of the logic area , and if you do some research you will find that this ammounts to almost half of a single core Die making the Dual Core CPU only a little more than 1/3 larger and with the appropriate 1/3 increase in powere consumption and thus heat . But and it is a big BUT with Intels CPUs reaching 120 watts thermal output at full load for the current fastest CPUs that would wind up at the substantial sum of 160 watts ( more than a soldering iron I use to repair Automotive radiators ) and that is going to be difficult to cool Quietly but not impossible ( 3kg copper cooler with 8 heatpipes and dual 120 mm panaflo fans - at 5 volt of course :lol: )
Small Fast and Silent - Quiet SFF With Gonads!

sthayashi
*Lifetime Patron*
Posts: 3214
Joined: Wed Nov 12, 2003 10:06 am
Location: Pittsburgh, PA

Post by sthayashi » Tue Sep 28, 2004 11:42 pm

pony-tail wrote:( more than a soldering iron I use to repair Automotive radiators )
IIRC from my computer architecture class several years ago, CPUs are reaching and maybe even exceeding heat dissipation per square inch of Nuclear reactors.
[size=75][url=http://www.twolf1300.net/sthayashi/SPCR/systems.html]My Power Rig, Storage Rig, HTPC and Main Rig[/url][/size]

silvervarg
Posts: 1283
Joined: Wed Sep 03, 2003 1:35 am
Location: Sweden, Linkoping

Post by silvervarg » Wed Sep 29, 2004 12:03 am

But and it is a big BUT with Intels CPUs reaching 120 watts thermal output at full load for the current fastest CPUs that would wind up at the substantial sum of 160 watts
Well, if you look at it from a CPu manufacturers perspective:
Lets assume you have a CPU core A with 100% performance and 100% heat.
If you underclock and undervolt the factory settings a bit you can typically reach 80% performance and 60% heat.
By throwing in another core you typically get 95% extra speed for ~33% extra heat.
So your new CPU could get 80%*195%=156% speed and 60%*133%=80% heat. So you could end up with more than 50% faster CPU that produce 20% less heat. The downside is that you used about 33% more die space, so cost is up ~33%. This is if you stay on the same manufacturing process. This looks like a fairly good deal, and it is far better than the benefits you get from hyperthreading.
[size=75][b]Passive XP2500+:[/b] Convection cooled, ~XP1500+, DP-102 cooler, Abit NF7-M, CNPS6000Cu on NB, Antec Overture, Samsung P80 120GB[/size]

stmok
Posts: 26
Joined: Fri Jul 09, 2004 2:35 am
Location: Sydney, Australia

Re: Any plans for dealing with dual cores?

Post by stmok » Fri Oct 01, 2004 8:49 am

mathias wrote:If dual core CPU's will be almost twice as hot, does anyone have any plans for cooling that silently?

I don't see what makes dual cores any different from dual CPU's, so if dual cores cause multithreaded software to become widespread, I think I'll get a dual CPU system instead. This plan seems so obvious to me, there has to be something wrong with it, so what am I overlooking?
Yeap, you are overlooking something. :)

The problem is, despite both Intel and AMD tooting about dual-core, they have failed to clarify about the thermal issue.

Nearly all PC enthusiasts I've come across talking to about dual-core haven't realised the following. (because both Intel and AMD have said very little about it).

The fact is, they will do the following to remain no hotter than today's CPU.

(1) They will NOT use regular voltage core like their single-core brothers.

They will use low voltage cores (CPUs that operate the same speed, but can run perfectly at a lower core voltage...Its like those used in mobile and embedded applications). Both AMD and Intel have low voltage versions of their Opteron and Xeon lines.

ie : Instead of one core CPU at 90W, you have two cores at 45W.
(In reality, it'll be a tad hotter for dual-core...About 93W)

(2) Dual-core CPUs will NOT run at the same speeds as their single-core brothers.

ie : Instead of single-core at 2.4Ghz, it'll be dual-core at 2Ghz.

The above two points are the most logical approaches (reduce speed and lower core voltage to maintain thermal cooling requirements of today's systems)...Its the same methodology adopted by some folks around here...Reduce speed (underclock) and lower core voltage to reduce thermal output.

Why do you think AMD has spec'ed their dual-core for 95W, whereas their regular single core Opterons are spec'ed for 89W?
(They represent the MAX that all Opteron mobos a spec'ed for...It doesn't represent the true value of an Opteron CPU at speed)..

This allows any Opteron mobo owner to simply install their new dual-core CPU, (need BIOS update) without worrying about anything else relating to cooling.

One other thing about dual-core...It will not perform the same as true dual CPU setup...Expect about a 10% performance drop compared to dual CPU. (This is because of a design compromise that must be done...eg : In AMD's case, the two cores are sharing the memory controller. In Intel's 1st generation dual-core Xeon, its bandwidth between two cores is shared. They need a bigger or faster pipe between the cores and Northbridge).

So, from a performance view...Assuming all same speed in a multi-threaded scenario. (highest to lowest)

Dual CPU => Dual core => single CPU with SMT (like P4/HT) => single CPU

Intel's dual-core designs will NOT have shared cache, if you look at Pentium-M "Yonah" and Itanium dual-core designs, its two separate cache, one for each core. Did any of you read about Intel Developer Forum 2004 (Sept Edition)?

I hope the above clears it up for you.

mathias
Posts: 2057
Joined: Sun Jul 11, 2004 3:58 pm
Location: Toronto
Contact:

Re: Any plans for dealing with dual cores?

Post by mathias » Fri Oct 01, 2004 12:30 pm

stmok wrote:
(1) They will NOT use regular voltage core like their single-core brothers.

They will use low voltage cores (CPUs that operate the same speed, but can run perfectly at a lower core voltage...Its like those used in mobile and embedded applications). Both AMD and Intel have low voltage versions of their Opteron and Xeon lines.
They can do that? I saw a diagram somewhere indicating they weren't going to double the entire core.
stmok wrote: One other thing about dual-core...It will not perform the same as true dual CPU setup...Expect about a 10% performance drop compared to dual CPU. (This is because of a design compromise that must be done...eg : In AMD's case, the two cores are sharing the memory controller. In Intel's 1st generation dual-core Xeon, its bandwidth between two cores is shared. They need a bigger or faster pipe between the cores and Northbridge).
That's quite helpful, and encouraging. Of course, XP's don't even have onboard memory controllers, but hopefully two mobile XP's will be sufficiently cheaper than an equivalent dual core to compensate for this.

silvervarg
Posts: 1283
Joined: Wed Sep 03, 2003 1:35 am
Location: Sweden, Linkoping

Post by silvervarg » Sun Oct 03, 2004 11:50 pm

hopefully two mobile XP's will be sufficiently cheaper than an equivalent dual core
This probably depends a lot on your timeframe.
AMD has announced dual core versions to come out 2H05, so they will hit the market about a year from now. At first they will like all new CPU's be quite expensive. It seems reasonable to guess that a single dual core CPU with motherboard will be less expencive than two single core CPU's with motherboard some time close to mid 2006.
[size=75][b]Passive XP2500+:[/b] Convection cooled, ~XP1500+, DP-102 cooler, Abit NF7-M, CNPS6000Cu on NB, Antec Overture, Samsung P80 120GB[/size]

Post Reply