Can the Piledriver update make a real
difference to AMD's CPUs?
When AMD was throwing around the specs of
its first Bulldozer chips we all sat up and took notice. After all, it was
AMD’s first new CPU technology redesign for an absolute age, and what it was
planning on doing with the new Bulldozer microarchitecture looked pretty darned
revolutionary.
Sadly for AMD though, its top chip could
barely keep pace with the second tier of Intel's Sandy Bridge CPUs. Then it
released the 22nm Ivy Bridge die-shrink and things got even more miserable for
the Texan chip company.
But, as we've seen over the last few
months, those AMD Bulldozer chips still have something to offer. Maybe not the
top-end eight-core FX-8150, but the great value and overclocking capabilities
of the six-core FX-6200 made it a tantalising prospect for anyone on a budget
looking to put together a gaming rig.
Value is core to this arrangement, and
being able to put together a decent AMD CPU/mobo combo for less than a Core i5
setup means that you get a good chunk of cash to spend on your graphics card.
In fact, it's the difference between being able to pick up a HD 7950 or a HD
7870. And we know which we'd rather have humming away in our machine.
Now, with the Piledriver update to the
Bulldozer architecture, we've got the latest FX chips hitting the market under
yet another codename: Vishera. Can the revised architecture close the gap on
the Intel Ivy Bridge rivals, and give its CPU range a performance shot in the
arm to match its value credentials?
Threadbare
Strap in, I'm going to talk about
architecture here. The original Bulldozer design was a pretty radical shift in
terms of the change from the Stars architecture found in Phenom. It created
Bulldozer modules with a pair of 'cores' in each, sharing some lower
utilisation silicon such as level-2 cache, fetch and decode components, while
the more vital, time-sensitive parts, such as the integer pipelines and level-1
cache were part of each 'core'.
In actual use though, this sharing of key
components meant that while multithreaded performance was improved, having so
many more threads of processing available meant the single threaded performance
was slower even than the Phenom chips that preceded it. That also meant gaming
performance was down the pecking order, and the competing Intel chips left AMD
trailing in their collective wake.
To try to amend this, AMD has gone and done
a little light restructuring of the Bulldozer modules via this Piledriver
update. We've seen the first implementation of this new design in the recently
released Trinity desktop chips, but this is the first time we've seen it in a
dedicated desktop design.
Essentially this isn't a major overhaul
just a few serious engineer-pleasing improvements such as better branch
prediction, better hardware prefetching and improved scheduling. There are some
other under-the-hood enhancements, but all in all it' s relatively low-level
stuff.
For the real architectural improvements
we’re going to have to wait for the arrival of the Steamroller update sometime
next year. That's set to give the individual 'cores' more dedicated hardware to
make them more like the traditional core design. Steamroller doubles up the
decode engines in a module, and should make for improved single threaded
performance.
Extra, extra
That's not to say the new Piledriver design
doesn't add any extra performance for your cash. In fact, this top-end FX chip
is hitting the ground running at 4GHz out of the box. Eight AMD cores running
at 4GHz not too shabby. Sadly though, the single-threaded performance hasn't
ramped up significantly, so don't get too excited about garnering any extra
gaming performance from this new chip.
The multi-threaded performance doesn't see
a huge change either in both segments then we're looking j ataroundl5 percent
extra processing speed. On the multi-threading side though, that slight return
isn't as much of an issue thanks to the impressive showing of the original
architecture.
When you consider that the new FX
processors are going to be coming out at around the same sort of price as the
Bulldozer chips, that's not a bad slice of extra speed. And with the resolutely
quad-core i5 3570K coming in around $32 more expensive than this eight thread,
quad-module FX-8350, you're going to be getting a substantial chunk more CPU
performance straight out of the box.
Throw any multi-threaded application at the
two rival processors and the AMD chip will soon show its dominance in that
arena. With the i5 getting around the same sort of figures in Cinebench as the
old FX-8150, the new Pile driver chip is a little over 15 per cent quicker.
That performance gap gets even bigger when you chuck the HD encoding benchmark
of X264 v4.0atthe pair with the FX-8350 getting almost 25 percent better
results than the Intel i5.
In fact, if you take the FX-8350's
multi-threaded performance in isolation, it's suddenly getting rather close to
the performance of the similarly eight-threaded Oalmighty Core i7 3770K. In
Cinebench the AMD chip is only a little over 5 per cent slower, and in X264
there's less than a single per cent difference between them.
It's impressive that AMD has managed to
close the performance gap this much in the multi-threading stakes.
With so many modern productivity programs
really taking advantage of the extra threads on offer in today's processors,
there would be very little return on the extra $160 you'd spend on the 3770K
versus the FX-8350.
Unfortunately for AMD, we simply can't take
the multi O threaded performance of our chips in isolation. Single threaded
prowess still counts for a lot, not least in gaming. And in gaming the Intel
CPUs still give a lot more - in our tests we were looking at an extra 10-15 per
cent.
With cash of course being no object to any
of us PC gaming types, we would always go for an Intel CPU to prop up the best
graphics card available. But if you don't have the vast salary of a PC tech
journo (cough) then value for money is absolutely vital. The fact remains that
an AMD platform is cheaper than an Intel one, and that gives you more money to
spend on your GPU. With a better GPU, the gaming performance gains garnered by
the Intel CPU architecture become practically irrelevant. Your graphics card is
most responsible for your gaming experience, so it makes sense to drop the most
cash on that.
