Why PowerPC?

**n00body** · 12-30-2005

*DISCLAIMER*: I did a search and nothing popped up. So I apologize in advance if this has been discussed before.

Does anyone have any idea why MS went the route of the PowerPC architecture? They have always been such staunch supporters of Intel that this decision perplexes me. Especially after Apple went on record that they found they were better off with Intel. Why didn't they just try a multicore Pentuim?

That being said, I like the route they took, but I'm just curious about why they took it. Any comments would be most appreciated.

**TMR_Net_Shark** · 12-30-2005

Power PC architecture is a lot more efficent then Intel's. It has the more "bang for the buck"

I mean sure, Intel processors are powerful and can get up to 4.25 GHz, but it's still not going to be better then PowerPC's.

**Hypx** · 12-30-2005

It was the cheapest. You can't really do triple-core with x86 without breaking the bank in terms of diesize or heat. IBM on the other hand, had this simple and cheap in-order processor that didn't sacrifice anything in the ways of FP power versus a high-end PowerPC chip. Plus IBM was willing to license it, which probably was the primary reason.

**n00body** · 12-30-2005

Thanks for the explanation guys. It just struck me as a little odd that MS was basically saying Intel's chips weren't right for gaming.

**TMR_Net_Shark** · 12-30-2005

Originally Posted by n00body

Thanks for the explanation guys. It just struck me as a little odd that MS was basically saying Intel's chips weren't right for gaming.

To be honest, they aren't really good for floating point math at all. You look at the charts and AMD outperforms Intel in the floating point math department.

And I don't think AMD is really interested in getting into the gaming biz.

**udontneed2know** · 12-30-2005

Well for the 360 atleast, they went with PowerPC as the main component due to time constraints. That is 99% of the reason. And of course because the POWER line is the best that IBM has under its belt currently so it was the obvious choice for them. Why Microsoft went to IBM instead of Intel or AMD is another subject, and I often wonder that myself. I personally think Microsoft paid IBM quite a bit to create the chip so they could get inside information on exactly what IBM was doing with the Cell processor. Microsoft heard Cell would be 8-9 processors, so Microsoft needed IBM to put out similiar numbers.

Was a clever plan by Microsoft but it kind of backfired. IBM didn't have enough time to really flesh out the whole architecture and well, you have what you have today. 3 generic in-order PowerPC cores sharing only 1MB of cache.

**TMR_Net_Shark** · 12-30-2005

I don't know, I still like 3 general purpose cores then just 8 cores that do specific things. 3 cores can do new or different type of processes, while cell needs to do what it will always do, graphics, AI, floating point math.

In the PC world 3 general purpose cores >>> 8 cores that do things already programed into them.

**sevendesigns** · 12-30-2005

TMR, this isn't the PC world.. and I don't agree. I don't agree, because they obviously had gaming in mind when building the Cell. So don't act like it's a slouch in that department. It obviously beats down whatever the Xbox360 has in it.

**udontneed2know** · 12-30-2005

Unfortunately for Microsoft though were talking about gaming consoles here. General purpose really has almost no use within the world of consoles. And logically each SPE can handle general purpose code as well, including housing an OS on each. Each SPE is pretty varied in its capabilities. It can handle graphics, OS's, general purpose code and limited branched code as well through the branch hints avaliable in the instruction set.

Aleman · 12-30-2005

All bickering aside, look at what the original Xbox was able to do with a piece of crap, off-the-shelf Pentium 3 (/Celeron) clocked at 733 MHz...

**Novaboy117** · 12-30-2005

OMG some of you guys r suck A**es step aside and take an unbiased look at the consoles. Goodgrief im pro-PS3 as much as the next guy but I also like the Xbox brand alot. and Aleman I assume your saying what the Xbox could do was impressive for this generation, right? Well if i assume correctly, what makes the processor that got it there a "piece of crap"? Anyways im not a techie like the rest of you seem to be, only because im too lazy to pour all my free time into fully comprehending the stuff, but from developer comments to specs reviewed endlessly to upcoming game trailers and vids the PS3 and The 360 seem to have a small gap between them, PS3 taking the lead of course, but its just that a "small gap" besides wasnt this thread about the 360 exclusively? Why was the cell srpung into the discussion. Anyways forgive me if i've roamed of topic a little but just my little rant.

Aleman · 12-30-2005

What I was trying to do was to put everything in perspective. The Xbox was a great console and pushed amazing games using that crappy CPU. Regardless of how the Cell compares to the 360 CPU, I'm saying that both are many times more powerful than current gen, so everyone should be happy

**psyonic** · 12-30-2005

Originally Posted by TMR_Net_Shark

I don't know, I still like 3 general purpose cores then just 8 cores that do specific things. 3 cores can do new or different type of processes, while cell needs to do what it will always do, graphics, AI, floating point math.

In the PC world 3 general purpose cores >>> 8 cores that do things already programed into them.

This is EXACLY the problem, many have got an idea ps3's cell is an narrow grapics processor of sort, and xenon in xbox360 is "general purpose".

But, both share the same features. Since an xenon is in-order, lack large instruction window, no out of order logic, simmiliar prefetch and branching as Cell, it is an mini cell, without any of its great advantages.

An comparison: An single core AMD64 got 3 sets of units doing cpu work, and logic to feed them. If an core got two treads in an xenon, and got same number of units running in whole cpu, and more brute vectorised power, than an PC amd64 dual core.

Cell will last way longer,probably many years i think, while xenon in xbox360 will lag behind the coming year's processors on PC in practice.

**Terarrim** · 12-30-2005

psyonic said

This is EXACLY the problem, many have got an idea ps3's cell is an narrow grapics processor of sort, and xenon in xbox360 is "general purpose".

But, both share the same features. Since an xenon is in-order, lack large instruction window, no out of order logic, simmiliar prefetch and branching as Cell, it is an mini cell, without any of its great advantages.

They Cell and the Xbox 360 share similar features but it is unfair to call it a mini Cell as there are large difference.

For example the VMX unit on the Xbox 360 CPU cores are different from the PPE on the Cell and the Power PC in that it has a 128bit 128registers. This alone makes the Xbox 360 in order more times more powerful at mathematical crunching than a AMD64 CPU. Most of the 115gflp theoretical rating of the Xbox 360 can be attributed to these upgraded VMX units.

The Xbox 360 CPU also has other features like an on die debugger for helping programmers. You will not find this on the Cell processor. Although we haven't had quite the detail of the PPE for the Cell like we have had for the SPE, as it stands the Xbox 360 CPU contains more features and is more powerful than the PPE (again largely because of the boosted VMX unit in the Xbox 360 processor).

The AMD 4400 dual core is only hitting 18gflp theoretical peak rating and this is far below the 115 gflp rating of the Xbox 360 CPU so the processor will be in contention for some time (even without taken closed architecture into consideration).

Novaboy117 said

but from developer comments to specs reviewed endlessly to upcoming game trailers and vids the PS3 and The 360 seem to have a small gap between them, PS3 taking the lead of course, but its just that a "small gap" besides wasnt this thread about the 360 exclusively? Why was the cell srpung into the discussion. Anyways forgive me if i've roamed of topic a little but just my little rant.

I have to disagree with this statement. The Cell is in order more powerful than the Xbox 360 CPU. The VMX unit in the Xbox 360 the powerhouse of the CPU cannot hope to compete with the Cells SPE's due to the fact they have to share bandwith with other internal CPU units and the issue of cache size and efficany (local store on SPE's are much more efficient). Some benchmarking has been done proving the Cell can reach at least 133 gflops (granted this was 8 SPE's) in realworld applications including FFT and Matrices calculations. With further coding the benchmarking for the cell will be push real world benchmarking results higher.

We have had no such benchmarking for the Xbox 360 CPU at present. However I cannot possibly see the Xbox 360 benching at over 70gflps due to its internal bandwith issues, the cache inefficanys and cache size. The programmers just will not be able to use the VMX unit of the Xbox 360 in the same way as the SPE's due to the fact that other programmes has to be run on units inside the same CPU and the Xbox 360 just hasn't got the flexibility of the Cell.

The general purpose argument is also pie in the sky. No one really clarifies what this means.

does it mean media SPE's can do this in order more times faster than other CPU's
does it mean sound/music (as above)
does it mean spreadsheets (SPE's are superb at number crunching why would this be slower on the cell?).
does this mean wordprocessing (SPE's can do decryption/incryption I'm sure its not going to have a problem with a spellchecker).
Physics? SPE's can outperform a Intel Xeon 8> at FFT a formula used for physics and can do large FFT calculations at 38gflps when the Xenon chocked (It did not have the processor power/resources to run the calculations
Graphics? 5 second graphical rendering and a high end server took 15 minutes
Digital Processing (including compression etc) again FFT shows that is in order times faster than SPE's.

As long as the programmers have the time and the will to program the Cell properly I can't see any application that would not benefit from the raw power of the Cell. The exception might be something like windows Vista but thats a huge amount of clunky coding that really has no place on an architecture that is trying to make things simpler and faster (at least in my opinion).

I would lastly like to add that the debbuging unit on the Xbox 360 CPU might make it easier for programmers to debug code but once the game is running this is just part of the die that is idling (I really do like the Cell's concept of simpler but raw power).

**Novaboy117** · 12-30-2005

^^^^^Well like i said im no Techie just running off of wut i most here from devs n trailers.

**n00body** · 12-30-2005

My thread was specifically pertaining to the 360 processor. I did not ask for a Cell debate, as that is better suited to the PS3 portion of the forum.

**Venger** · 12-31-2005

MS had a couple reasons for going powerPC...though of course I'm speculating.

1) PPC chips tend to be cheaper at high speeds than Intel chips
2) PPC chips tend to perform better for the watts and the speed than Intel chips
3) PPC chips might make it harder to hack 360 than xbox1 was and make it harder to run linux on the system
4) Sony was going with IBM on a PPC based platform, and MS was both hoping Cell was a myth or that IBM had something else that could match Cell
5) PPC in this case is in order like the pentium 1 based celerons in xbox1

That help?

**Terarrim** · 12-31-2005

Maybe Intel and AMD were less willing\more expensive to create a custom chip for a console than IBM.

I would also think that IBM have more experience of creating custom chips than AMD and Intel. And would be more agile to produce the chip from concept, design and production to final stages than Intel and AMD. I think AMD and Intel would be much more reluctant to change portions of their chips to as these companies tend to be quite jealous in regards to their chip designs.

However this if just pure speculation. As far as I'm concerned they made the right choice because a 115gflp theoretical rating CPU is still way more power than either AMD or Intel are pushing at the moment.

[edit]
I do apologize for not directly responding to the topic n00body, however I felt the need to both defend the Xbox 360 (mini cell indeed) and disagree with a statement about the Cell so I hope you expect this post as my apology

.

**n00body** · 12-31-2005

No worries Terarrim.

I was just worried that the post would trail off from the topic like quite a few other threads.

Anyway, thanks for all the well-thought input.

**Shred0r** · 12-31-2005

SUN’s UltraSparc T1 - the Next Generation Server CPU

Holy....SUN has released recently info on their new Sparc CPU with 8 cores. it sucks only 70-80W and has in a specific operation field a 300% efficiency of an Dual Core Opteron 64 Server CPU....

They could rule the server market with this baby.

SUN is going to shine once again...

http://www.anandtech.com/cpuchipsets...oc.aspx?i=2657

**n00body** · 12-31-2005

Shred0r, this is not related to the topic. Could you please go post it in the technology forums instead?

**dbakerstl** · 12-31-2005

Originally Posted by n00body

Shred0r, this is not related to the topic. Could you please go post it in the technology forums instead?

I would disagree - It just shows where technology is going instead of HUGE powersucking GP CPUs for everything, whats the point of having 3 GP cores on a CPU (unless you can virtualise them to run 3 different OSs) I dont see the need - you only need one GP core and the rest should be fore hardcore processing. And going back to MS use of PowerPC -- well its simple since Altevec has been around for a while they thought they could get away with GP cpus and then increase proformance by taking avantage of the altevec stuff on the PPC cores, but it is a complete WASTE of gp cpus, and in my opinion they prob will not be using most of the capabilities of their 3 core CPU simply because of the fact that many of the registers in the CPUs are general purpose and really have no merit for consoloe programming...

**CompGeek** · 01-04-2006

2 Reasons, and these are the ONLY 2. Doesnt hve anything to do with the PowerPC architecture being more idel.

It was cheaper.

IBM was willing to sell MS te rights to produce the chips.

IF the 360 had used an Athlon 64 it would be significantly more capable at AI and Physics calculations. But AMD wasn't about to let their chips be manufactured by another company... so IBM is what they got.