The size of the eDram and is said to be
large enough to hold frame buffers at
about 128MB. With that said, let’s talk
overclocking!
HASWELL FREQUENCY
CONTROLS - THE DETAILS
For the Core frequency, INTEL added
an additional register for turbo
multipliers increasing the theoretical
maximum multiplier value from 63X to
80X. The BCLK frequency increments
are still the standard 1MHz steps and
the voltage is programmable via the
iVR (more on that later). Note that
opening up the CPU ratio registry to
80X is not a guarantee that the CPUs
can reach such a speed (8GHz). As
INTEL states, its engineers look for
ways to give as many tools as possible
for users to find the physical limits of
their design with no arbitrary limits.
Regarding BCLK frequency, Haswell
brings the same BCLK gear ratios to
us as featured on the X79 platform
but absent on Ivy Bridge. In case you
did not know, about a year ago INTEL
stated that there was simply not
enough time to add the gear ratios to
Ivy-Bridge when questioned about
their absence. It is not simply a matter
of just "adding the options". The gear
ratio requires an additional DB1200
clock multiplier in the CPU package not as simple as it sounds!
With Haswell, the gear ratio
selection includes options for 1x,
1.25x and 1.67x as BCLK "multipliers",
giving you an offset of 100MHz,
125MHz or 167MHz. For those who are
wondering, the BCLK gear ratios are
fully functional with S3 sleep state
enabled. This means your Haswell
system is able to resume from S3
with the BCLK ratio overclocked.
For those who wonder if Haswell
supports the 2.50x gear ratio that
was also available on the early X79
motherboards, the answer is yes
and no. Yes, theoretically, it might be
possible to use a 5:2 PEG/DMI ratio
which is the 2.50x BCLK gear ratio.
Implementation however depends on
the motherboard vendor. We will find
out when the products launch.
The leeway for BCLK adjustments,
for each gear ratio is similar to what
Ivy Bridge offered: about five to seven
percent either way. On Ivy Bridge, the
highest BCLK frequency we have seen
so far is 117MHz (+17%) and there is no
reason to assume this will be worse
on Haswell. So perhaps we might see
a 195MHz BCLK frequency.
Completely new for Haswell is
gaining control over the Ring Bus
frequency. In simple terms, you can
see this ring bus frequency as the new
"uncore frequency" - although that
is technically incorrect. The ring bus
is adjustable with ratios up to 80X as
with the CPU. Typically, it is clocked
“Regarding BCLK frequency, Haswell brings the
same BCLK gear ratios to us as featured on the X79
platform but absent on Ivy Bridge.”
32 The OverClocker Issue 24 | 2013