Testing Conditions
To see how the ST46F performs under pressure, we threw a high-end HDTV HTPC system at it.
1 SilverStone ST46F (460 Watt) PFC Power Supply
1 AMD 2600 XP (333FSB) (Which takes 75 Watts, P4 northwood 3.2GHz takes 89 Watts)
1 MSI KT4V-L Motherboard
2 256MB PC2700 DDR RAM modules
1 NVidia FX 5200 128MB
5 200GB Maxtor 7200 RPM 8MB Cache hard drives (running raid 0,1 and 5 with 940GB of 1TB disk array usable)
1 10GB IDE 5400 RPM Western Digital Hard drive (running as idle)
3 pcHDTV OTA HDTV Linux Tuner cards
1 Audio Excel 5.1 Sound card
2 DVD-ROM drives
1 IDE-PCI controller to connect 4 more IDE devices.
This is more hardware than what you would find in a typical server. But SilverStone claims it can do this, so lets find out.
As a good comparison, we will compare the ST46F to the Antec True Power 380, famed for it's stability. Although the ST46F is rated higher than the Antec 380, the Antec True Power 380 is not your typical power supply and can power more hardware than many 400 or higher Wattage PSU's. Both PSU's were subjected to the same system loads and the stability is what we are looking for. When applications start to run and access hard drives, memory, and CPU, this is were we can see how stable a power supply is.
Antec True Power 380
VCore: +1.67 V
+3.3V: +3.27 V
+5V: +4.98 V
+12V: +11.94 V
-12V: -12.33 V
-5V: -5.08 V
SilverStone Tek ST46F
VCore: +1.67 V
+3.3V: +3.32 V
+5V: +4.91 V
+12V: +12.24 V
-12V: -12.09 V
-5V: +3.51 V
Antec True Power 380 strengths:
The +12V and +5V ran closer to their respective rails and were slightly more stable. It also has a -5V which the ST46F does not.
SilverStone Tek ST46F strenghts:
Everything else. The rest of the voltage rails on the ST46F were closer to their respective rails and much more stable. The +12V and +5V rails on the ST46F you will notice have interesting characteristics. As the +5V becomes stable, the +12V looses it's strong stability. It just so happens it is when the processor is at full load that the +5V line jitters slightly, and the +12V stabilizes. When the CPU becomes idle, the +12V rail jitters and the +5V stabilizes. All power supplies have an optimal load, where they are the most stable. Seeing the +12V stabilize at high load, which the CPU uses, it would appear that with all the hardware in this computer, it may be using less power than what the optimal draw from the power supply is. This is great news for Overclockers.
If you look closely at the ST46F chart, you will notice that the -5V rail is absent. -5V is not used on newer computers. The -5V rail had been used for amplifiers in the past but you are not likely to find new hardware today requiring it. Just incase though, I contact SilverStone who said they can make the -5V active if requested by distributers. My system runs just fine, but I do admit I pause when I read the +3.5V on the -5V line, but this is most likely the motherboard not understanding the absence of -5V. After weeks of 24x7 use of the system, there have been no problems of any kind.
The +12V rail, running at +12.24, is off by 2%, but this is very acceptable. The rest of the voltages are off their rails less than 1%, which is very impressive, especially for powering all this hardware. As a note, most computer hardware is designed to tollerate up from 5%-10% offset from their desired voltage rails. It is the high amounts of jitter that are more likely to cause problems for hardware. The voltage rails on the ST46F varried by no more than .3%, the True Power varried by 1.2%.
The ST46F is over 70% effecient in converting AC power to DC power, so it draws less power than most PSU's which are around 60% effecient (The True Power 380 is about 71%-74%). The ST46F also shares power between different voltage lines, so it is not possible to max out all the voltage rails like you could on the True Power 380. However, the ST46F is more stable which is quite interesting. If you aren't familiar with how PSU's share power between different voltages, you should read Power Supplies: The shocking truth!.
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