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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kiwidude - Wednesday, October 12, 2011 - link
I think this shows what a great job Intel have been doing more than confirming your insulting comment about AMD engineers.JohanAnandtech - Wednesday, October 12, 2011 - link
"Brand new and spanking Bulldozer has it roots in ancient K6"There is some K7 heritage left, but I can not see in any way how this CPU relates to the K6! The K6 had a very short pipeline, a unpipelined FPU for example.
As when it comes to the server market: AMD seems to have overclocked and cherry picked the 3.6 GHz FX-8100. For the desktop market, clockspeed rules, so AMD didn't care too much about power consumption.
For the server market, they can go with lower clocked 95 W TDP parts. These should have a much better performance/watt ratio. Also, the server market runs at 30-80% CPU load, the desktopmarket runs a few cores at 100%. So the powermanagement features will show better results in the server market.
The gaming software needs fast caches (latency!) as IPC is decent. The server software is more forgiving when it comes to cache latency as IPC is more determined by the number of memory accesses and thread synchronization. That is the reason why that L3 is so handy. I think you should wait to condemn bulldozer until it is has been benchmarked on our server benchmarking suite.
I am worried about the legacy HPC performance of this chip though.It will take some recompiling before the chip starts to shine in this market.
FunBunny2 - Wednesday, October 12, 2011 - link
Had to get this far in the comment thread for sanity. Clearly, AMD (and one may disagree) has chosen to go for superior integer performance in a threaded architecture. D'oh! So what? It means they don't give a rat's rectum about gamers. They care a whole lot about application and database servers. They also accept the fact that single threaded is dying, so just kill it.Makaveli - Wednesday, October 12, 2011 - link
I stayed up and read this its 2 in the morning excellent review as always anand.But instead of back to the future its back to the P4???
Why AMD WHY for the love of everything holy!
Sind - Wednesday, October 12, 2011 - link
Disappointing.. I hope they can get it together with the aggressive road map.wolfman3k5 - Wednesday, October 12, 2011 - link
I know, right. I'm also patiently waiting for the AMD Bendover architecture. Maybe it will be competitive, who knows...kiwidude - Wednesday, October 12, 2011 - link
Hi, the CPU Specification Comparison chart has incorrect info listed under X6 1100T and X4 980 NB clocks. Great review as always love your work.wolfman3k5 - Wednesday, October 12, 2011 - link
NewEgg doesn't even have any Bulldozers in stock, at all. Not the AMD FX 8150 or AMD FX 8120. I guess that no one is in a hurry to grab one...enterco - Wednesday, October 12, 2011 - link
Hell, Amazon UK doesn't have any Bulldozer neither...ckryan - Wednesday, October 12, 2011 - link
Maybe Newegg filed them under Server CPUs where BullDozer belongs.