The Bulldozer Review: AMD FX-8150 Tested
by Anand Lal Shimpi on October 12, 2011 1:27 AM ESTCache and Memory Performance
I mentioned earlier that cache latencies are higher in order to accommodate the larger caches (8MB L2 + 8MB L3) as well as the high frequency design. We turned to our old friend cachemem to measure these latencies in clocks:
| Cache/Memory Latency Comparison | ||||||
| L1 | L2 | L3 | Main Memory | |||
| AMD FX-8150 (3.6GHz) | 4 | 21 | 65 | 195 | ||
| AMD Phenom II X4 975 BE (3.6GHz) | 3 | 15 | 59 | 182 | ||
| AMD Phenom II X6 1100T (3.3GHz) | 3 | 14 | 55 | 157 | ||
| Intel Core i5 2500K (3.3GHz) | 4 | 11 | 25 | 148 | ||
Cache latencies are up significantly across the board, which is to be expected given the increase in pipeline depth as well as cache size. But is Bulldozer able to overcome the increase through higher clocks? To find out we have to convert latency in clocks to latency in nanoseconds:
We disable turbo in order to get predictable clock speeds, which lets us accurately calculate memory latency in ns. The FX-8150 at 3.6GHz has a longer trip down memory lane than its predecessor, also at 3.6GHz. The higher latency caches play a role in this as they are necessary to help drive AMD's frequency up. What happens if we turn turbo on and peg the FX-8150 at 3.9GHz? Memory latency goes down. Bulldozer still isn't able to get to main memory as quickly as Sandy Bridge, but thanks to Turbo Core it's able to do so better than the outgoing Phenom II.
L3 access latency is effectively a wash compared to the Phenom II thanks to the higher clock speeds enabled by Turbo Core. Latencies haven't really improved though, and Bulldozer has a long way to go before it reaches Sandy Bridge access latencies.
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ET - Wednesday, October 12, 2011 - link
I gather you're trying for a job at AMD.wolfman3k5 - Wednesday, October 12, 2011 - link
Even the most hardcore AMD Fanboys are having a hard time defending this bulldozed Bulldozer chip.I have seen people blaming anything from Global Foundries to saying that "It's not all that bad."
If you're an AMD Fanboy in Denial, you should read what's wrong wigt Bulldozer:
1) AMD's marketing is extremely misleading, because Bulldozer is not more of a Quad Core chip than Intel's Core i7 for example. What AMD did was to create a crude implementation of CMT (chip-level multithreading), which is debatable as of now if it's any better than Intel's Hyper Threading, with the mention that Hyper Threading takes less than 5% of DIE Space per Core. Basically each Module (as AMD likes to call its Cores now) has an additional Integer Unit, but the problem is that the additional Integer Unit shares the Fetch and Decode units with the other Integer Unit in the Module. Ergo, the CPU is not a true 8 Core. It is just a cheap AMD marketing gimmick.
2) The reason for the horrendous single threaded performance is the poor design of the Integer units in the modules (you can interpret this as very low IPC count). Couple that with the fact that two Integer Units share the same Fetch and Decode units, and when one additional thread is added that screws things up and the pipeline needs to be flushed, it messes things up for the other Integer Unit as well. At a bare minimum AMD should have added a Fetch and Decode unit for each Integer Unit. But wait, if they would have done that, then they would have needed to add a dedicated FPU for each separated Integer unit. Hell, this is almost worst than Hyper Threading. At least Hyper Threading makes use of unused resources in the CPU. AMD's implementation can leave resources unused.
Bottom line: no matter how you slice and dice it, the Bulldozer chip cannot be called an 8 core chip. It's a 4 Core CPU with CMT.
3) In order to compensate for the design flaws in each Module (what I've described in point no. 2), AMD increased the L2 cache to almost absurd levels for each module, to mask some of the latency created by their poor CMT implementation. Intel's Sandy Bridge does away with 256KB L2 cache per core. Hence, we have ~1.6 Billion Transistors in Bulldozer, which creates leakage, which in turn translates into high power draw. Those of you that defended this failure of a CPU claiming that it was designed for servers should know that Performance / Watt is all that matters for servers, because you run into cooling issues otherwise, which translate into high energy costs both for the servers themselves and for the cooling which is done mostly by Air Conditioning. And we all know that Air Conditioning draws lots of electricity.
Bottom line: it's not Global Foundries fault, it's AMD's fault for not designing a more efficient CPU with less transistors (Sandy Bridge quad core has ~1.12 Billion).
Belard - Wednesday, October 12, 2011 - link
Those are excellent points.Its like AMD decided to DO EVERYTHING wrong that Intel and Nvidia did and put it all onto a single chip!!
The Fusion CPUs provided small size, good performance and excellent GPU at a good price. Bulldog is a mutt of a mess.
Brinip - Wednesday, October 12, 2011 - link
After years of being an avid amd fan. I finally switched this year to Intels sandybridge CPU. Amd could no longer compeat with the pure power of the sandybridge core.I was really hoping the bulldozer would re-write the books and put amd back on an even footing. In some ways they have re- written the books as the architecture of the new CPU is quite a change, however for now at least they don't pose ant threat to Intels superb sandybridge core.
Not only are sandybridge CPUs fast, they are also fairly low power and run very cool. What more can you say really. Fast, cool and efficient.
Perhaps as amd develop it further then improvement may come, however don't expect intel to sit still either.
LordConrad - Wednesday, October 12, 2011 - link
Looks like AMD jumped on the NetBurst bandwagon. My next computer build will be Intel.Artas1984 - Wednesday, October 12, 2011 - link
QUOTE:I was hoping for Bulldozer to address AMD's weakness rather than continue to just focus on its strengths
UNQUOTE
And while the new chip does feature a slight improvement in mutli-threaded apps, it's pound per pound performance is slower than AMD Phenom II X6 1100T
8 core, 32 nm, 8 Mb L2, 3600 MHz CPU SLOWER than 6 core, 45 nm, 3 Mb L2, 3300 MHz!!!
Seriously...
W H A T T H E F U ^ K I S T H I S S H I T???
But it's not a big deal. There are greater problems in this world that cpu debates. At least we have AMD and Intel. Imagine if there was only one company making processors - my god that would be a problem then...
ClagMaster - Wednesday, October 12, 2011 - link
The Bulldozer would be a dynamite server processor provided the OS was optimized for the cores that are available.I think the processor has real potential but needs further optimization with a latter stepping.
As for PC useage, performance of the FX-8150 is not bad but I could do better with an i7-2500. I am a low power person and if I were opting for a PC upgrade tonight at NEWEGG, I would choose the i5 2400S and a X68 Intel motherboard.
jaygib9 - Wednesday, October 12, 2011 - link
I don't know about the rest of you, but personally, if I'm going with an 8 core CPU, I'd go water cooling anyhow. Air cooled pc's should be on their deathbed and water cooling should be the norm. AMD and Intel are leaving more CPU's unlocked for overclocking anyhow. What do you think the performance would look like at 5 GHz/core compared to stock speeds?jaygib9 - Wednesday, October 12, 2011 - link
Personally I wonder if soon they'll require water cooling and quit worrying so much about the TDP(within reason of course), then they can concentrate on the clock speed.Belard - Thursday, October 13, 2011 - link
Geee... a 25% overclock for the fake 8-core CPU will not make up for the 30~50% performance disadvantage over a cheaper $200 intel CPU.THAT is a serious problem.
Water cooling is stupid, in general. Less than 1% of desktop computers have water cooling. They will fail sooner or later.