[Socially Awkward Solo]

Since Motorola is slow as all hell to come out with faster CPU's do you think Apples next step will be 3 processors in the box?

[:XI:]

is it possible to have 3 cpu comps? i've only ever seen 1/2/4/8 cpu comps.*

*ok, so i've only actually seen 1 and 2 cpu computers. but i know they only seem to come with an even number of cpus.

[Thain Esh Kelch]

It isnt possible due to the architecture.

[D'Espice]

Theoretically, 3-processor machines are possible however it'll never happen. Especially since the two processors are being held back by the slow Frontsidebus (nowaday 166 MHz isn't even enough for one single CPU). Imagine four microprocessors having to share one single 166 MHz bus... it'll be like CPU overkill

[Eug]

Plus I'd guess that the 1.25 GHz G4 7455 chips would cost about CAD$500 each.

I'm betting on the 7457 making an appearance by summer 2003, and PPC970 in 2004.

[krove]

Like someone mentioned, what would be the point with the current state of the frontside bus?

[Slaveway]

Originally posted by krove:
Like someone mentioned, what would be the point with the current state of the frontside bus?

I would hope Apple will be working on that problem.
There is so much room for improvement with the computer regardless of getting faster chips.

[D'Espice]

Originally posted by Slaveway:
I would hope Apple will be working on that problem.
There is so much room for improvement with the computer regardless of getting faster chips.

They certainly are... however the MPC74xx and the MPX bux-protocol do not support DDR-FSB therefore Apple will be stuck to SDR-FSB as long as they are going to use the Motorola G4 processor.

[Eug]

Originally posted by D'Espice:
They certainly are... however the MPC74xx and the MPX bux-protocol do not support DDR-FSB therefore Apple will be stuck to SDR-FSB as long as they are going to use the Motorola G4 processor.

I thought the fabled 7457-RM supports DDR (not the plain 7457). (Not that I'm saying it actually exists yet.)

[Superchicken]

we'll be lucky to see 1.5 Ghz CPUs with Firewire 800 and so on and so forth.

[MindFad]

Originally posted by Superchic[k]en:
we'll be lucky to see 1.5 Ghz CPUs with Firewire 800 and so on and so forth.

I bet we'll see that in the next few days. Or at least before the end of February. I'll bet fifty cents on it.

[Amorph]

Originally posted by Eug:
I thought the fabled 7457-RM supports DDR (not the plain 7457). (Not that I'm saying it actually exists yet.)

If the rumored descriptions about the -RM suffix are true, it will support DDR by default, since it will have an on-die memory controller and connect to the rest of the board via RapidIO instead of a conventional bus.

Once freed of MaxBus, Apple could hook a 7457-RM up to whatever memory technology they wanted, because no matter how it comes out of the physical RAM it'll end up getting wrapped in packets and sent across the RIO bus, and vice versa.

The 970 has a similar approach: It's not that its bus supports DDR so much as the bus is completely abstracted from the RAM, and supporting a given memory technology will basically involve a little ASIC to translate between the 970's packet-based bus and whatever interface the RAM uses.

[Socially Awkward Solo]

Originally posted by Thain Esh Kelch:
It isnt possible due to the architecture.

So why can't they change it?

[Eug]

Originally posted by Socially Awkward Solo:
So why can't they change it?

Because the G4 7455 can't support it, as others have already said.

We have been waiting for years for Motorola to make new chips that would, but so far it hasn't happened.

[Leia Shoots Like a Girl]

Originally posted by Eug:
Because the G4 7455 can't support it, as others have already said.

We have been waiting for years for Motorola to make new chips that would, but so far it hasn't happened.

Stange, I thought the whole point of the G4's is that they can support more then 1 prosessor, I didn't know the limit was 2!

[D'Espice]

There is a difference whether a microprocessor is specified to run in an Dual processor machine or in an machine with more than two microprocessors. The Intel Xeon for example is only specified for DP machines, only the Intel Xeon MP will run in MP machines with more than one microprocessor.

[Catfish_Man]

Originally posted by Leia Shoots Like a Girl:
Stange, I thought the whole point of the G4's is that they can support more then 1 prosessor, I didn't know the limit was 2!

Oh they'll support more than two (in theory), they just won't support three (or any odd number). They use something called "symmetric multiprocessing", and it requires an even number of processors. Also, more than 2 G4s would suck big time, since none of them would be able to get enough data. The PowerPC 970 has a separate pair of busses for each processor, and is designed for up to 8 way multiprocessing.

[D'Espice]

Originally posted by Catfish_Man:
Oh they'll support more than two (in theory), they just won't support three (or any odd number). They use something called "symmetric multiprocessing", and it requires an even number of processors. Also, more than 2 G4s would suck big time, since none of them would be able to get enough data. The PowerPC 970 has a separate pair of busses for each processor, and is designed for up to 8 way multiprocessing.

That is so not true. Symmetric Multi Processing has absolutely nothing to do with whether the number of processors is odd or even, nothing at all.

Symmetric Multiprocessing, as opposed to Asymmetric Multiprocessing, means that the available microprocessors (even or odd) are working on one task simultaneously. This means that avaliable tasks and threads are being assigned to one of the two microprocessors, so that - in an ideal world and application - both processors are fully loaded all the time which would result in almost twice the performance. Mac OS X and all other UNIX operating systems as well as Windows NT4, Windows 2000 and Windows XP support SMP.

Asymmetric Multiprocessing is different, a microprocessor is assigned one specific application or task not controlled by the operating system. It's hard to describe the exact difference without an example, so here you go: Mac OS 9 is not capable of utilizing more than one microprocessor. However Photoshop for Mac OS 9 does, it enables the AMP by directly accessing the second CPU, bypassing the operating system's routines. In this case, the operating system controls the first CPU, the application controls the second CPU.

I guess you could say that the basic difference is that SMP has to be supported by the OS as well as the application to get the best results (Multi-Threaded architecture) whereas AMP has to be supported only by specific applications and is much more complicated to implement.
Again, neither of these techniques has something to do with odd or even count of microprocessors.

[Ken_F2]

That is so not true. Symmetric Multi Processing has absolutely nothing to do with whether the number of processors is odd or even, nothing at all.

Most mp chipsets, including the one apple uses, do not support an odd configuration of processors (>2).

[D'Espice]

Originally posted by Ken_F2:
Most mp chipsets, including the one apple uses, do not support an odd configuration of processors (>2).

I did not deny that because this is a chipset, not microprocessor issue. Catfish_Man however blamed it on the word "symmetric" saying that symmetric multiprocessor machines need even numbers, which is not true.

[Eug]

Originally posted by Leia Shoots Like a Girl:
Stange, I thought the whole point of the G4's is that they can support more then 1 prosessor, I didn't know the limit was 2!

If anyone with more knowledge would care to comment feel free to jump in. But here are my 2 (three?) cents as an undereducated peon:

What I was getting at was that it'd be somewhat of a waste of time to put three CPUs on a such a slow bus. Unfortunately, the current G4 7455 doesn't support currently available faster memory designs (ie. DDR). I don't think the 7457 does either, but supposedly the vapourware 7457-RM does.

The benefit of the 7457 is faster CPU speeds and lower power utilization, and the benefit of the 7457-RM is even faster speeds AND support for DDR (or whatever) and potentially lower power utilization (although more than the 7457). Another problem of the 7455 is that it seems that Motorola intended it to max out at 1 GHz. So it seems we're lucky even to have 1.25 GHz chips.

Thus we are up the creek until one of these new chips shows up. In the very least if we got a 1.3-1.5 GHz 7457, it might eliminate the fan noise plaguing current PowerMacs. (Then again it might not, I dunno.) However, it would still be limited by the memory architecture to a certain extent. It'd be nice to jump directly to 7457-RM, but I highly doubt that would be the case. Rumours are such that 7457-RM is not supposed to come out until after the 7457. Mind you, one wonders if the 7457 is now moot, since we already have 7455 chips at 1.25 GHz, and the 7457 is supposed to max out at 1.3 GHz. The 7457-RM was supposed to start at 1.3 GHz and go up to about 1.8 GHz.

The PPC970 won't be out for a while, but is supposed to start at 1.4-1.8 GHz, but rumours have it that 1.8 GHz of a PPC970 will be much faster than 1.8 GHz in a G4 7457-RM.

And of course having 3 chips of any design would be absurdly expensive for a simple home computer even if it's supposed to be a "pro" one. Dual machines are already making Macs pricey. I'd hate to see Apple having to resort to triple or quad CPUs in a PowerMacs, and dual in a laptop.

[normyzo]

Originally posted by Catfish_Man:
Oh they'll support more than two (in theory), they just won't support three (or any odd number). They use something called "symmetric multiprocessing", and it requires an even number of processors. Also, more than 2 G4s would suck big time, since none of them would be able to get enough data. The PowerPC 970 has a separate pair of busses for each processor, and is designed for up to 8 way multiprocessing.

Contrary to popular belief, you can support odd # of processors in SMP. For example, take the ALR 6x6. 6 Pentium Pros, at either 180Mhz or 200Mhz.

Actually, its kind of cheating, because ALR came up with a scheme to use 6 when everyone else could only use 4. Basically, they grouped the processors into 2 groups of 3 and then the "4th" processor in each group of 3 was actually the _other_ group So yes, you do need a power of 2.

Dan

[Simon]

Originally posted by normyzo:
Contrary to popular belief, you can support odd # of processors in SMP. For example, take the ALR 6x6. 6 Pentium Pros, at either 180Mhz or 200Mhz.
...
So yes, you do need a power of 2.

I don't want to be a smart ass here, but 6 is not an odd number. It isn't a power of two, but that doesn't meen it's odd.



Odd = 2m+1 or 2m-1 where m is in Z
Even = 2m where m is in Z

Power of two = 2^m where m is in N

Now, a really strange SMP example would be a machine with 3 or 5 CPUs. Neither an even number nor a power of two, but I have never heard of such a thing. Anybody know an example?

[Tritium]

Sun E420rs run just fine with 3 processors in them...

[Spliffdaddy]

Originally posted by Tritium:
Sun E420rs run just fine with 3 processors in them...

I thought the ALR Revolution 6X6 used three sets of CPU riser cards - each with 2 CPUs.

I also found out you can run 3 Xeons (p2/p3) in a 4-way server.


edit. oops, quoted the wrong individual...