lower than the CPU core frequency. As
INTEL stated, they had not recorded
much of a performance increase from
overclocking the ring bus frequency,
but did hint at the possibility of the its
frequency frequency affecting overall
system stability. It will be interesting
to see what overclockers (i.e. you) will
come up with.
As we know, Ivy Bridge featured
somewhat mediocre memory
overclocking. That is, if we compare it
to the AMD record-breaking memory
overclocking capabilities. DRAM
frequency overclocking seems to
have improved with Haswell as INTEL
is officially supporting memory all
the way up to DDR3-2933. Although
several Z77 motherboards already
support the DDR3-2933 ratio, it is not
official. Having this ratio supported by
INTEL is in fact a step forward as this
means it passed the internal validation
and qualification process at this rated
speed. Nice!
Last but not least is the IGP clock
frequency that remains unlocked.
INTEL provides a ratio as high as
60X, in 50MHz steps. This means a
theoretical maximum overclock of
3GHz. Given the GT2 can reach about
2GHz under extreme cooling; we do
not expect the more complex GT3e
to reach that 3GHz number, but who
knows? Overclocking has never been
an exact science.
“Last but not least is the IGP
clock frequency that remains
unlocked. INTEL provides a ratio
as high as 60X, in 50MHz steps.”
HASWELL VOLTAGE CONTROL THE IVR OPTIONS
One of the more significant changes in
Haswell - at least for tech enthusiasts
- is of course the integration of the
Voltage Regulation as mentioned
earlier. On previous architectures,
the CPU had several external voltage
regulation units each powering one
of the various parts of the CPU. There
was a separate VR input for the Core
voltage (Vcore), IO (VIO), Graphics
processor (Vgfx), System agent (Vsa)
and the PLL clock generator (Vpll).
With Haswell, this changes. Instead of
having separate Voltage input signals,
INTEL has merged them all into a
single one.
This single input goes by Vccin
and serves as input voltage for the
integrated voltage regulation (iVR).
It supports up to 3.04V input, which
means a lot of current can be driven
into the CPU. The iVR uses the input
to distribute voltage to the various
parts inside the CPU. Unlike what
many feared, INTEL has not limited
the voltage options for overclocking.
You can still deliver all the way up to
2.0V to the cores. The ring and the
integrated graphics support a 500mV
offset for the system agent and the IO.
The rules for overvoltage on Haswell
are similar to Ivy Bridge with one very
important exception:
As a rule of thumb, the Vccin should
be at least 400mV higher than the
Vcore. In other words: Vccin >= Vcore
+ 400mV.
HASWELL VOLTAGE CONTROL THE OVERVOLTAGE OPTIONS
One aspect of overvolting and
overclocking Haswell the speakers
were very proud of was the available
possibilities for fine-tuning your system
Issue 24 | 2013 The OverClocker 33