AMD FX-8120
‘If
you use air cooling for Bulldozer, we predict it will be rather noisy.’
The desktop version of AMD’s new 32nm
Bulldozer is called Zambezi and has a single HyperTransport link, while server versions
of Bulldozer are named Valencia and Interlagos. For the purposes of this review
we’ll simply refer to Bulldozer and specifically we’re talking about the
FX-8120 and FX-8150.
AMD
FX-8120
The internal arrangement of Bulldozer
consists of a number of modules that each have two cores and 2MB of L2 cache.
In the case of FX-8120 and FX-8150, all four modules are enabled, which puts
this piece of silicon in a different league to every other desktop processor on
the market. These are eight genuine hardware cores, with none of those
Hyper-Threading shenanigans that make a quad-core CPU appear to have eight
cores (Intel core i7, we’re talking about you).
Lesser Bulldozer have six or four modules
(FX-6xxx and FX-4xxx), which appear to be eight-core CPUs with one or two modules
fused off. It’s not clear whether these are processors with failed modules or
whether AMD has killed off perfectly decent cores in order to create a range of
processors that starts at $135 for FX-4100 and climbs to $390 for FX-8150.
AMD has made the upgrade path easier for
its customers by adopting socket AM3+ for Bulldozer, which is backwards
compatible with Phenom II. Put another way, if you have an AM3+ motherboard
with a Phenom II, you can drop in a Bulldozer and add more cores in a matter of
moments.
Alternatively, you can trade off the number
of cores for higher clock speed as, for example, the quad-core FX-4170 runs at
an epic 4.2GHz.
AMD has taken a similar approach to Intel
Sandy Bridge by treating Bulldozer as a bucket of performance that operates
inside certain power and thermal limits. The cores can raise their clock speed
using a Turbo function to respond to an increase in workload until to hit the
thermal limit.
At the launch of Bulldozer, there was a
single model, the 3.3GHz FX-8150, which has eight cores and runs at 3.3GHz with
a Turbo limit of 4.2GHz and a price of $390. Unfortunately, the FX-8150 isn’t a
particularly good processor, despite its impressive clock speed. For one thing,
it draws 200W under load but only delivers performance that is similar to Core
i5-2500K. Your reviewer is a convert to closed loop water cooling systems from
the likes of Corsair and Antec, because they’re small a neat, but it’s an
essential requirement for Bulldozer. If you use air cooling on Bulldozer, we predict
it will be rather noisy and will probably reduce performance.
The specific problem appears to be that
Bulldozer is designed to make full use of its many cores and isn’t very good
operating on one or two threads. Unfortunately, Windows appears to make a mess
of assigning the workload to ensure that Bulldozer can shut down processor
modules that are not required at any particular moment.
The situation has improved with the launch
of FX-8120, which also has eight cores, a slightly lower clock speed of 3.1GHz
and a significantly lower price of $225. During our testing we found that
FX-8120 would happily run at the same 4.2GHz that we got from FX-8150 when
FX-8120 offers the same performance for half the price.
The obvious problem is that Core i5-2500K
does the same job while using considerably less power and it even comes with
integrated graphics. Sorry Bulldozer, you need to try harder.
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Details
Price: $225
Manufacturer: AMD
Website: www.amd.com
Required
spec: Socket AM3+, dual-channel DDR3
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