XVME-6500
USER
’S MANUAL
Acromag, Inc. Tel: 248-295-0310
- 22 -
http://www.acromag.com
- 22 -
www.acromag.com
3.2.2 Programmable CPU Power Limits
The XVME-6500 features programmable power limits, allowing the user to
'dial-down' the maximum power consumption of the CPU in systems where
power is a concern. The graph below shows that the i7-4700EQ CPU
outperforms other available embedded Intel CPU's at every power point from
5W - 47W, even the i5-4402E, which can also use the programmable power
limits.
By simply programming a lower power limit in the BIOS setup, the CPU can be
used in applications where less power is available or heat removal is an issue.
This is accomplished by the CPU automatically underclocking its frequency to
maintain a power level at the set limit.
Note:
Once the minimum frequency of 800MHz is reached the programmed
limit could be exceeded. Extremely large workloads have a realistic minimum
power of around 20W. However light to medium workloads can effectively
maintain a power limit as low as 5-10W.
There are two programmable CPU limits. These are the long-term average
Power Limit 1 (PL1) and the short-term Power Limit 2 (PL2). Depending on a
windowed Power Limit 1 Time 'constant', the CPU can spend a short time
above power level PL1 up to a maximum of PL2, allowing a significant
performance boost for short workloads. If the CPU power remains above PL1
at the end of this time the power is then limited back to PL1. The power must
drop below the PL1 limit before it allowed to increase back to PL2 again. For
time spent above PL1 an equivalent amount of time must be spent below PL1
in order for it to rise again to PL2. The maximum time could be as much 2.5x
the value of PL1 Time.
CPU
M
ar
k
Power Rating or Throttle Setting (W)
i7-4700EQ (5-47W)
i5-4402E (5-25W)
i7-3612QE (35W)
i7-3615E (45W)
i7-3517UE (17W)
Atom E3845 (10W)
