[chrisutley]

We need to buy another Mac for the office, and I want to make sure I understand the difference between the dual cores in the PowerMac and new Intel iMac.

It's my understanding that the PowerMac dual core is effectively (2) processors, so you get true SMP. Now is it true that the new dual core iMacs do not support SMP?? If this is really the case, I think lots of people are confused when it comes to "dual core".

[mduell]

Unless you're (not you necessairly, but the general "you") being excessively pedantic, dual core is just having two CPU cores on the same package.
Both the PowerMacs (with 2 G5 cores) and the iMac (with two Pentium M cores). Both share a FSB among the two cores. The PowerMac has 1MB cache for each core, while the iMac has 2MB cache shared between the two cores (which can be more efficient). Both are considered SMP.

[jamil5454]

Which makes me wonder...

The new 20" iMac gets you roughly the same power and somewhat more features than the low-end PowerMac, all for a cheaper price. And you get a 20" Cinema Display as a bonus.

Sounds like a good deal unless you absolutely need the internal expansion.

[chrisutley]

So then I read this in the iMac thread and I'm left scratching my head again.

"From what I've read, Intel is developing another chip called Sossaman that is like Yonah but allows higher-end capabilities like SMP."

What I want to know is will the machine (Intel iMac) effectively be utilizing 2 processors more or less the same way the PowerMacs do, yielding benefits when multi-tasking and running MP aware apps. OR is the new iMac processor seen by the iMac is a single processor?

Pedantic? Shawshank Redemption anyone?

Originally Posted by mduell

Unless you're (not you necessairly, but the general "you") being excessively pedantic, dual core is just having two CPU cores on the same package.
Both the PowerMacs (with 2 G5 cores) and the iMac (with two Pentium M cores). Both share a FSB among the two cores. The PowerMac has 1MB cache for each core, while the iMac has 2MB cache shared between the two cores (which can be more efficient). Both are considered SMP.

[mduell]

Originally Posted by chrisutley

So then I read this in the iMac thread and I'm left scratching my head again.

"From what I've read, Intel is developing another chip called Sossaman that is like Yonah but allows higher-end capabilities like SMP."

What I want to know is will the machine (Intel iMac) effectively be utilizing 2 processors more or less the same way the PowerMacs do, yielding benefits when multi-tasking and running MP aware apps. OR is the new iMac processor seen by the iMac is a single processor?

Yes.
Possibly more effectively, since the cores share an L2 cache while the PowerMacs have two seperate half size) caches.

[Catfish_Man]

Originally Posted by chrisutley

So then I read this in the iMac thread and I'm left scratching my head again.

"From what I've read, Intel is developing another chip called Sossaman that is like Yonah but allows higher-end capabilities like SMP."

What I want to know is will the machine (Intel iMac) effectively be utilizing 2 processors more or less the same way the PowerMacs do, yielding benefits when multi-tasking and running MP aware apps. OR is the new iMac processor seen by the iMac is a single processor?

Pedantic? Shawshank Redemption anyone?

The dual core chips will behave just like every other dual core chip. The SMP support they are talking about is for dual dual core chips.

[chrisutley]

Originally Posted by Catfish_Man

The dual core chips will behave just like every other dual core chip. The SMP support they are talking about is for dual dual core chips.

Okay, so what I'm getting from all this is that the Intel iMac is not the equivalent of a dual processor machine.

[Weezer]

no, it is the equivalent. It's just not 2 seperate processor chips, they are on the same dye. You will get the multi-tasking, etc, you want from a dual with the dualcore chips.

[rhashem]

Originally Posted by chrisutley

Okay, so what I'm getting from all this is that the Intel iMac is not the equivalent of a dual processor machine.

The Core Duo is a dual-core processor, just like the current dual-core PowerMacs (the Dual G5's actually only have a single physical chip now). It is designed to have two processors with a shared cache. From the software's point of view, it is exactly the same as a dual-processor machine. You can run two seperate programs at once, and each will have a whole CPU to itself, or you can run a program with multiple threads, two of which can run simultaniously. It's not like Intel's Hyperthreading, in which one CPU's resources are shared by two threads --- in Yonah, there are two physical sets of CPU resources.

The difference between the Core Duo and a regular dual-processor machine (like the old PowerMac) is that the two processors are manufactured onto the same piece of silicon. This is actually an advantage, because this means they can use very high-speed on-chip communications, instead of using slower off-chip communication as you have with an SMP machine that has two seperate physical processors.

[chrisutley]

Originally Posted by rhashem

From the software's point of view, it is exactly the same as a dual-processor machine. You can run two seperate programs at once, and each will have a whole CPU to itself, or you can run a program with multiple threads, two of which can run simultaniously.

I'm surprised that Apple would give this capability to a consumer Mac, as it seems to be a logical differentiator for Pro/Consumer.

[rhashem]

Originally Posted by chrisutley

I'm surprised that Apple would give this capability to a consumer Mac, as it seems to be a logical differentiator for Pro/Consumer.

Apple has no choice. With Yonah, and the upcoming Merom/Conroe, Intel is pushing dual-cores at all levels, except for the very low-end Celeron replacements. AMD has already started to phase out the single-core FX chips, and is planning on releasing a dual-core Sempron (their budget line). By the end of this year, dual core processors are going to be standard in the iMac's price bracket. So instead of releasing a castrated single-core iMac, Apple did the right thing and beat the rest of the industry to making dual-cores standard in the new Intel Macs.

[Catfish_Man]

Originally Posted by chrisutley

Okay, so what I'm getting from all this is that the Intel iMac is not the equivalent of a dual processor machine.

That's the opposite of what I said, actually. The iMac is the equivalent of a dual processor machine, as are all other dual core machines.

[mduell]

Originally Posted by chrisutley

I'm surprised that Apple would give this capability to a consumer Mac, as it seems to be a logical differentiator for Pro/Consumer.

I expect all the desktop pro Macs to go quad when they switch to Intel (or shortly thereafter), just like they switched to all dual with the second or third revision of the G5 PowerMacs.

[chrisutley]

Originally Posted by Catfish_Man

That's the opposite of what I said, actually. The iMac is the equivalent of a dual processor machine, as are all other dual core machines.

This is what threw me...

"The SMP support they are talking about is for dual dual core chips."

Dual Dual Core chips?

[Busemann]

Originally Posted by chrisutley

This is what threw me...

"The SMP support they are talking about is for dual dual core chips."

Dual Dual Core chips?

Dual dual = Quad (two dual core processors)

[Cadaver]

Originally Posted by mduell

I expect all the desktop pro Macs to go quad when they switch to Intel (or shortly thereafter), just like they switched to all dual with the second or third revision of the G5 PowerMacs.

I'm not sure that Apple will necessarily go dual-processor+dual-core (like in the G5 Quad). Intel is developing higher-performance dual-core processors; the Core Duo™ (aka Yonah) is really a mobile & small form factor chip. The up-coming chips (Merom & others) are more desktop-oriented chips based higher performance architecture. I'd expect Apple to use those instead. Among other things, it will have 4MB of cache (vs. the Core Duo's 2MB) and Intel's 64-bit instruction set (which the Core Duo and Core Solo don't have).

By going with Intel, Apple now will have a lot of different choices in terms of processors... unlike the old days with Motorola and IBM, where the only way Apple could boost performance was to add more processors. A dual core Merom will probably be better in terms of "power-per-Watt" than a 4-core Yonah system.

[mduell]

Originally Posted by Cadaver

I'm not sure that Apple will necessarily go dual-processor+dual-core (like in the G5 Quad). Intel is developing higher-performance dual-core processors; the Core Duo™ (aka Yonah) is really a mobile & small form factor chip. The up-coming chips (Merom & others) are more desktop-oriented chips based higher performance architecture. I'd expect Apple to use those instead. Among other things, it will have 4MB of cache (vs. the Core Duo's 2MB) and Intel's 64-bit instruction set (which the Core Duo and Core Solo don't have).

By going with Intel, Apple now will have a lot of different choices in terms of processors... unlike the old days with Motorola and IBM, where the only way Apple could boost performance was to add more processors. A dual core Merom will probably be better in terms of "power-per-Watt" than a 4-core Yonah system.

Merom is also a portable chip. Conroe is the desktop counterpart and Whitfield is the workstation (SMP capable) chip using the same architecture (INGM).
If I recall correctly Merom is expected to improve on performance per watt by about 30% over Yonah (Yonah improved over Dothan by nearly 100%, in part due to the process shrink). There will also be Kentsfield, two Merom dies on the same package (quad core in one socket).

[rhashem]

Originally Posted by Cadaver

I'm not sure that Apple will necessarily go dual-processor+dual-core (like in the G5 Quad). Intel is developing higher-performance dual-core processors; the Core Duo™ (aka Yonah) is really a mobile & small form factor chip.

I agree with you, but I have to make a correction: Merom is a laptop chip, based on a brand new architecture. Conroe is the desktop chip based on Merom. You're right that this is probably the distinction that Apple will make: Merom in iMacs and laptops, Conroe in workstations. These will all be dual-core chips, since these chips don't support SMP. Apple might keep a dual dual core in their lineup, but such a computer will have to be based on Woodcrest, the Xeon replacement based on the Merom architecture.

In general, I'd expect the difference between iMacs and PowerMacs to become smaller, so they mirror the natural constraints of the form factors of each machine --- the PowerMac will have the highest-clocked (and thus hotter) CPUs, more expandability, more RAM support, etc. Apple won't, in general, be able to get away with the large deltas between lines they've had in the past (G4 versus G5, single core versus dual core). People won't want to buy $1500 iMacs (twice the cost of the average desktop PC) if they use a previous generation processor.

[Todd Madson]

After I bought my DP 2.5 machine I quickly came to the realization
that I would never willingly buy a single CPU system again.

This is a big win for the consumer who wants a decent amount of
power without having to pay $3,000.

Realize too that there are two technologies involved: SMP -
symmetric multiprocessing and pre-emptive multitasking.

You can have pre-emptive multitasking on a single CPU
system but you can only have SMP on a two processor
system or a dual core system.

What's the difference:
single core dual processor = two physical processors.

dual core processor = two (or more) processors on a single die.

I will be eager to see how things go in the future. I love
my dual G5 but I must admit the power bills have been
much higher than I'd like to see.

This is where Intel will help - faster machines with lower
power consumption/heat generation.

[wee_ag]

So in looking at the PM G5 vs the new iMac dual - do we have any comparisons in performance? All I've seen is the PS benchmark which I keep hearing is not optimized for dual core and not a good evaluation.

Do we have any real-world tests of the new iMac to compare with the dual-core PM's? I'm trying to decide between the new iMac, a current PM or wait for the new intel PM.

[Bwa]

I just bought an iMac Intel 17" base model. I also have a dual processor (single cores) G5 @ 2 GHz. Subjectively, the iMac is slower. It bogs down when ripping a CD, streaming to an AirPort Express, and scrolling images in Safari. It may be memory bound; the iMac has 512 MB of RAM vs 1.5 GB in the G5 (not exactly an ocean of RAM in either place).

The iMac is a wonderful piece of engineering, as is the G5 tower.

I think it comes down to the age old advice: If you need a monitor too, and don't need expansion, the iMac may be the right choice for you. If you have the physical space available for a large tower, require expansion slots, or already own the desired monitor(s) you want, then the G5 might be the best choice.

And of course, buy a computer now if you need one now. If you don't need one now, wait. :-)

My 2c.

[OreoCookie]

I wouldn't trade in a dual PowerMac for an Intel iMac just yet. Right now, there are only a few native applications. And if you emulate photoshop on an Intel Mac, it's going to be slower than a dual G5. Obviously this is going to change over the course of this year, in particular when Apple's Pro apps are available as Universal Binaries. But then I expect that you can buy PowerMacs with Intel cpu which should be (considerably) faster than an iMac.

Also, keep in mind that the perceived boost in performance is not as big if you pretend for the moment that Apple would have included a dual core G5 in the iMac. Together with IBM's latest compilers (which are only available for Linux), the two machines should perform on par. I know this is a highly hypothetical argument, but the benchmarks I have seen seem to suggest that the biggest improvement over the previous generation of iMacs is the inclusion of a second core.

[otakujosh]

I will be purchasing the second generation macbook pro in the fall when i get my student refund check, if it is a yonah instead of a merom, do you guys think the motherboard would support upgrading to a merom when they come out?

[mduell]

Originally Posted by otakujosh

I will be purchasing the second generation macbook pro in the fall when i get my student refund check, if it is a yonah instead of a merom, do you guys think the motherboard would support upgrading to a merom when they come out?

The chipset/platform (Napa) will support Merom (since Santa Rosa won't be out until 6mos after Merom launch), but there is no guarantee the firmware will support Merom. Also, the CPU is soldered in the MBP, so changing CPUs would take quite a bit of work.