WINDOWS 11
& THE THREAD
DIRECTOR
The difficulty with a hybrid CPU design like
Alder Lake is that it requires a certain amount
of intelligence in both the hardware and the
software to make everything run optimally.
With a top-tier part like the 12900K, sending
latency-sensitive or demanding workloads
to the E-cores could make the system feel
sluggish while sending less demanding work
to the P-cores can burn extra power.
Ideally, the CPU needs to schedule lighter
tasks to the E-cores and heavier tasks that
require real-time responsiveness to the
P-cores. When something wants to use the
maximum computing power of the processor
and spawns dozens of threads, then it can use
both P-cores and E-cores. Intel has created a
hardware solution that’s responsible for this
decision-making, called the Thread Director.
The Thread Director uses a trained AI
model to identify different workloads at the
chip level and can provide telemetry data to
the OS so that it knows where to send work.
The problem is that Windows 10 uses static
scheduling of threads and while it may be
aware of hybrid cores, it doesn’t query the
telemetry data the CPU provides to determine
where to send work. This can result in a
less than perfect experience when running
Windows 10 on an Alder Lake CPU with both
P-cores and E-cores, and the solution is to
simply run Windows 11.
Windows 11 uses the full feature set of the
Thread Director. That’s the good news. If you
plan to buy an Alder Lake CPU or a prebuilt
Alder Lake system, you should plan on using
Windows 11. But as we’ve noted already, that
can be a bit of a contentious point. Windows
11 makes enough changes to the UI and
user experience that quite a few people are
seriously put off with Microsoft’s latest OS.
Alternatively, you can still run Windows
10, and Intel claims that the difference in
performance usually only amounts to a
few percent. We set about testing that, and
while many applications show performance
fluctuations of less than five percent, there
are enough exceptions that it’s a concern.
We saw what can only be classified as a
terrible performance from Alder Lake—both
the i9-12900K and i5-12600K—in Corona,
y-cruncher (single- and multi-threaded modes),
POV-Ray (single- and multi-core), HandBrake
x264 encoding, and more. Using Windows
10, there are quite a few cases where the
12900K falls behind even the Ryzen 5 5600X
and previous generation i5-11600K, and the
12600X performs even worse. Run those same
tests on Windows 11 and Alder Lake often tops
even AMD’s fastest Ryzen 9 5950X.One of the main issues appears to be
Windows 10 scheduling any threads
designated as lower priority to the E-cores,
regardless of how much CPU time they’re
using. It’s possible to work around these
problems using various utilities to prevent
certain applications from running with
a low priority level, but that gets messy
and confusing for a lot of people. Patches to
the various software packages might also
improve the situation in the coming months.
For the time being, we strongly recommend
using Windows 11 as the foundation of any
Alder Lake system.PCI EXPRESS 5.0
Alder Lake will be
the first consumer
platform to support
PCIe Gen5 devices, but
actual support may
vary by motherboard
and processor. We
know that most
Z690 motherboards
theoretically have
support for PCIe Gen5,
but we don’t have the
hardware to test that
support just yet. Both
the latest graphics
cards and the latest M.2
SSDs are still sitting
in Gen4 land, but we
should see Gen5 SSDs
at least arrive this year.
One thing we don’t
expect is widespread
support for PCIe
Gen5 on laptops. In
fact, right now most
shipping laptops are
still using PCIe Gen3
SSDs because the
minor gains in normalworkloads from a
faster Gen4 SSD
don’t measure up to
the increased power
requirements and loss
of battery life.
It’s an interesting
change in position
for Intel, after being
late to the PCIe Gen4
party—support for
that only arrived
with Rocket Lake and
Z590 processors and
chipsets. AMD already
supported Gen4 with
its Zen 2 Ryzen 3000
processors, launched in
2019, two years ahead
of Intel’s 11th Gen CPUs.
Now Intel is ahead of
AMD, as well as Nvidia
and the various SSD
providers. Most people
won’t need that doubled
bandwidth any time
soon, but it will be
beneficial in the data
center.Also note that Intel
doubled the speed
of the DMI interface
between the chipset
and the CPU with Alder
Lake. It’s basically the
equivalent of a PCIe
Gen4 x8 interface now,
double the bandwidth
of the DMI 3.0 x8
interface on Rocket
Lake and quadruple the
bandwidth on Comet
Lake and earlier chips.
That wider interface
means motherboards
can hang more Gen4
M.2 slots off the PCH
and still have full
performance on any
attached SSDs.Samsung has already
teased an upcoming
PCIe Gen5 SSD.
There’s no word yet on
performance, but the x4
interface provides up to
15.7 GB/s of throughput.FEB 2022 MAXIMU MPC 33
© SAMSUNG