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Review: Rosewill Tachyon-750

by Tarinder Sandhu on 15 January 2013, 21:00 3.5

Tags: Rosewill

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Testing results

Our testing procedures can be found at this link.


Load 10pc 25pc 50pc 75pc 100pc
Efficiency 84.3pc 91.5pc 92.7pc 90.2pc 90.0pc

Efficiency, as expected, is very good from 25 per cent to 100 per cent load. The numbers are a little better than the AX760 at low loads but a smidge worse at 75 per cent and 100 per cent loads.


In terms of regulation, we're looking at just how well the supply is able to hold to the various lines. The ATX spec. has a +/- 5 per cent leeway on all but the -12V line.

Line/Load 3.3V 5V 12V
10 per cent +1.1pc +1.3pc +1.2pc
50 per cent +0.8pc +1.1pc +0.5pc
100 per cent 0pc +0.3pc -0.1pc

Most supplies overvolt with little load and undervolt when stressed. The ATX specification is simply too lenient to trip-up any high-quality supply. Underscoring this, we've not had a single PSU fail the ATX specification thus far, though do understand that any PSU with a total leeway of below two per cent is considered to be premium quality. In particular, the 100 per cent load figures are exemplary.

Regulation - cross-load

How about providing uneven loads that stress particular voltage rails? In the first attempt, we've put 60A on the 12V rails, and 1A on the 3.3V and 5V rails. This can actually be somewhat typical for a system heavy on graphics and CPU power. In the second, we've turned the tables and gone for 12A on both the 3.3V and 5V rails - highly unlikely in a real-world environment - and just 2A on the 12V - even more unlikely!

Line/Load 3.3V 5V 12V
Cross-load 12V focus +1.3pc +1.4pc -0.8pc
Cross-load 3.3V/5V focus -0.9pc -0.5pc +0.6pc

Hammering one part of the PSU power delivery while using just a small portion of the other can throw cheaper supplies of out kilter. There's little variation going on here; you're looking at just over two per cent from a best-to-worst-case scenario. Following on from the regular tests, anything below three per cent is premium.


Line/Load (mv - p-p max) 3.3V 5V 12V
10 per cent 5mV 10mV 15mV
50 per cent 10mV 10mV 15mV
100 per cent 15mV 15mV 25mV

The ATX v2.2 spec states that the maximum permissible ripple is 120mV for the 12V line and 50mV for others.

PSUs convert AC power into DC, but doing so requires the AC waveform to be suppressed. What we're really testing here is the quality of the supply's rectifier and any smoothing capacitors in getting rid of this unwanted up-and-down ripple - the raison d'être of this supply.

Suppression of ripple is marginally better than the Corsair AX760's - read excellent - but both PSUs are well, well within the tolerances ascribed by the ATX spec.


Temperatures Intake Exhaust
10 per cent 27°C 32°C
50 per cent 33°C 38°C
100 per cent 38°C 46°C

Temperatures are good to excellent for the three tested settings.

Fan performance

Temps are good but they mean little in isolation. Obtaining accurate noise readings is near-on impossible when the supply is connected to the Chroma test harness and dual-unit load-tester. We can test the manufacturer's quietness claims in a different way, by using an AMPROBE TMA10A anemometer placed directly over the centre of the PSU. The anemometer records the airflow being pushed/pulled from the PSU's fan. We can use a Voltcraft DT-10L RPM meter to measure the rotational speed of the fan, too.

Load Fan RPM Airflow Noise
10 per cent 550rpm 19.5cfm Quiet
50 per cent 750rpm 34.6cfm Quiet
100 per cent 1,100rpm 63.5cfm Noticeable


As usual, we also installed it onto our high-end PC, equipped with a GeForce GTX 680, and ran through a few games. The 140mm Globe Fan, while active, is not noticeable during regular gameplay.