Since every system and environment is different, I ran back to back tests between the Apogee XTL and the HD to show how they compare. For those interested in how I achieved exact numbers, the ambient temperature was 21°C during testing. Pump speed was regulated via PWM based on a pre-set "silent" motherboard option, and fans are using 5V power for reduced noise. AMD Cool'n'Quiet is enabled for reduced speed and voltage at idle, and two overclocked speeds were tested under load; 3.9GHz (245x16) at the stock 1.3V, and 4.3GHz (245x17.5) at 1.5V to the CPU. Temperature readings were measured using the motherboard sensor rather than the CPU die, due to irregular offsets used by AMD.


At stock voltage, idle temperature under both blocks was 29°C, only 8°C over ambient. At this temp, the PWM controlled pump was registering 2200rpm. Once full load was applied and the system run for ten minutes, pump speed climbed as high as 3350rpm, while the temperature under the XTL block registered 49°C and the HD block was 2°C less.


Increasing voltage by two tenths and bumping the speed up to 4.3GHz causes the idle temperature to rise, but here we see a 2°C difference between the two blocks. The spread increases to a 4°C difference at full load, with the XTL block allowing the CPU to exceed 60°C. Pump speed registers from 2375rpm at idle, up to 4325rpm under load, nearly reaching the maximum 4500rpm ceiling. Despite the higher temp, the system was still stable using either block, however it's likely that under certain circumstances the cooler-running Apogee HD could yield a higher overclock.

Let's wrap things up with some final thoughts and conclusion.