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Now, as we all know Bulldozer performs like crap in its current iteration, there's no excuse and believe me, what I'm posting here isn't an excuse. Any posts saying that it is will be reported and hopefully deleted by our friendly moderating team. This is infact a my thoughts on the Bulldozer architecture as a whole and why Zambezi sucks so hard at the moment.
Note: I don't claim to be an expert with CPUs, this is what I think is affecting performance from BD going from what I've read and what I know.
1) Cache thrashing & Latency: This review from Anandtech shows that L2 and L3 cache latency is horrible, L2 cache latency being nearly double Intels and L3 cache latency being over double. What does this mean for performance? It means that it takes longer for data to get to the cores, combined with the small L1 cache that is used by many cores at once vs by two at most...Well, it makes for a messy scenario, I'm willing to bet a lot of the time the pipelines are doing nothing while waiting for data to come from the cache.
2) CPU scheduling and software: Bulldozer is an entirely new chip, I doubt AMD pulled anything from Thuban/Deneb apart from x86 compatibility, history has shown us (Three separate examples, all from Intel, seriously. Read up on your history if you call this an excuse, I can come up with more if you really want) that new architectures tend to suck when they first come out with the second generation parts being far better (For reference, Pentium 75/90 and the Pentium II. That site is owned by a very reputable store in my home town) I think the same will hold true for Bulldozer, especially since it seems to fare better in Linux than Windows, not to mention this post...There is heaps of room for improvement, and AMD could easily do it.
3) Power consumption: Now, this is a doozy of an issue, a CPU pulling easily nearly 500w alone? There's something wrong there, extreme leakage doesn't seem like it's it either or these chips would require LN2 to come stock...However there is evidence suggesting (Not proving, we need more evidence) that it may be an issue with the CHV motherboard and BD.
4) Delays, delays, delays: We all know BD was delayed 2 quarters from when it was meant to launch, and we all know Trinity with the Piledriver cores is launching in Q1 2012 assuming there's no issues or delays. We also know now (Assuming you didn't before) that history shows that new architectures tend to suck on their first outing and that Llano is AMDs main source of revenue. Now, there were rumours that AMD delayed BD due to Llano yields being bad which I believe (Along with BDs performance), but a friend of mine pointed out something that could very well be true...What if Bulldozer is a pipe cleaner product?
AMD have done it before to great success, BD is a new architecture and the compilers (Intels compiler, gcc, etc) need to get some optimization for this architecture, its not like it used to be where you could get the previous generations one and still get decent performance.
One example of optimization would be to make threads go on either only even or odd cores until they absolutely have to use the others. (Eg. If your program uses 4 cores, use core 1, 3, 5 and 7 on a FX-8150 for max performance but then use cores 2, 4, 6 and 8 when needed)
AMD launching BD, as much of a failure as it is, would make the devs of the various compilation tools at least get a basis for optimization, as well as optimization in the OS for BDs cores, as such, Bulldozer isn't meant to be the product that destroys everything, Piledriver is but they launched Bulldozer to get the worst parts of a new arch out of the way earlier.
They also could have delayed Bulldozer to put more engineers on Piledriver, but after all, it looks like software (Time fixes this) and the cache are what limits BD, I wouldn't be surprised if Piledriver is very good.
Once again, please don't post "This is excuse making!" There is no excuse for BDs performance, but there are reasons for why it is this bad, if any fanboys start posting about Intel in here (This has nothing to do with Intel, so don't say "My i5 is better!" for example) and it goes out of control, I'll PM a mod for a lock, please just discuss possible reasons why BD is slow in here. Excuse the incoherence in some areas, I'll rewrite this after I've had a bit of a good sleep.
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Note: I don't claim to be an expert with CPUs, this is what I think is affecting performance from BD going from what I've read and what I know.
1) Cache thrashing & Latency: This review from Anandtech shows that L2 and L3 cache latency is horrible, L2 cache latency being nearly double Intels and L3 cache latency being over double. What does this mean for performance? It means that it takes longer for data to get to the cores, combined with the small L1 cache that is used by many cores at once vs by two at most...Well, it makes for a messy scenario, I'm willing to bet a lot of the time the pipelines are doing nothing while waiting for data to come from the cache.
2) CPU scheduling and software: Bulldozer is an entirely new chip, I doubt AMD pulled anything from Thuban/Deneb apart from x86 compatibility, history has shown us (Three separate examples, all from Intel, seriously. Read up on your history if you call this an excuse, I can come up with more if you really want) that new architectures tend to suck when they first come out with the second generation parts being far better (For reference, Pentium 75/90 and the Pentium II. That site is owned by a very reputable store in my home town) I think the same will hold true for Bulldozer, especially since it seems to fare better in Linux than Windows, not to mention this post...There is heaps of room for improvement, and AMD could easily do it.
3) Power consumption: Now, this is a doozy of an issue, a CPU pulling easily nearly 500w alone? There's something wrong there, extreme leakage doesn't seem like it's it either or these chips would require LN2 to come stock...However there is evidence suggesting (Not proving, we need more evidence) that it may be an issue with the CHV motherboard and BD.
4) Delays, delays, delays: We all know BD was delayed 2 quarters from when it was meant to launch, and we all know Trinity with the Piledriver cores is launching in Q1 2012 assuming there's no issues or delays. We also know now (Assuming you didn't before) that history shows that new architectures tend to suck on their first outing and that Llano is AMDs main source of revenue. Now, there were rumours that AMD delayed BD due to Llano yields being bad which I believe (Along with BDs performance), but a friend of mine pointed out something that could very well be true...What if Bulldozer is a pipe cleaner product?
AMD have done it before to great success, BD is a new architecture and the compilers (Intels compiler, gcc, etc) need to get some optimization for this architecture, its not like it used to be where you could get the previous generations one and still get decent performance.
One example of optimization would be to make threads go on either only even or odd cores until they absolutely have to use the others. (Eg. If your program uses 4 cores, use core 1, 3, 5 and 7 on a FX-8150 for max performance but then use cores 2, 4, 6 and 8 when needed)
AMD launching BD, as much of a failure as it is, would make the devs of the various compilation tools at least get a basis for optimization, as well as optimization in the OS for BDs cores, as such, Bulldozer isn't meant to be the product that destroys everything, Piledriver is but they launched Bulldozer to get the worst parts of a new arch out of the way earlier.
They also could have delayed Bulldozer to put more engineers on Piledriver, but after all, it looks like software (Time fixes this) and the cache are what limits BD, I wouldn't be surprised if Piledriver is very good.
Once again, please don't post "This is excuse making!" There is no excuse for BDs performance, but there are reasons for why it is this bad, if any fanboys start posting about Intel in here (This has nothing to do with Intel, so don't say "My i5 is better!" for example) and it goes out of control, I'll PM a mod for a lock, please just discuss possible reasons why BD is slow in here. Excuse the incoherence in some areas, I'll rewrite this after I've had a bit of a good sleep.
