Bargain Hardware Thread

[Madpoo]

Originally Posted by Xyzzy

Can you compare a light bulb load to a computer load? (We don't know!)

Is this link useful?

http://www.allaboutcircuits.com/text...e-ac-circuits/

A lightbulb wattage and the wattage of a PC should be "close enough". A tungsten bulb is nearly all resistance (not much inductance, nothing to write home about anyway).

A modern switching power supply will "approximate" a resistive load, but then I think there's a rule of thumb/fudge factor of 97% or so. I can't remember where I saw or read that, but that's in my brain for some reason.

Clamp type ammeters (which is basically what you're using) are generally close enough... it would be weird to be off by 50% though. You might try one of those Kill-A-Watt plugin things. I'm not sure, but I'd guess those are shunt-type measurements of the current, and they do fairly well for high inductive loads like refrigerators/freezers, for example.

[kladner]

A modern switching power supply will "approximate" a resistive load, but then I think there's a rule of thumb/fudge factor of 97% or so. I can't remember where I saw or read that, but that's in my brain for some reason.

I think you are referring to Power Factor. A PF of 1 is non-reactive, i.e.: resistive. Power Factor indicates how close the current and voltage peaks align. Less than 1, current lagging voltage, is an inductive load. Current leading voltage is a capacitive load, or a PF over 1. While PF and efficiency in a motor are not quite the same, PF does affect losses in transmission. For the same amount of power (watts), larger currents flow when the PF is not equal to 1, because some of that power is being drawn at a lower voltage, and
Power = e*i, voltage times amps.

Large installations use various means to correct their overall PF. These can be capacitor banks, or certain kinds of electric motor which can be set up to have a capacitive (current leading voltage) effect

[retina]

Originally Posted by kladner

... a PF over 1 ...

... is not possible.

[kladner]

Originally Posted by retina

... is not possible.

Current can lead or lag voltage.

EDIT: But I guess the effect is the same. Out of sync is out of sync.

[retina]

Originally Posted by kladner

Current can lead or lag voltage.

You are correct, it can. But the PF value is always <=1.

[kladner]

Originally Posted by retina

You are correct, it can. But the PF value is always <=1.

Admitted.

[LaurV]

Originally Posted by retina

You are correct, it can. But the PF value is always <=1.

Not if you are perendev...

[bgbeuning]

Originally Posted by Madpoo

You might try one of those Kill-A-Watt plugin things.

A Kill-A-Watt says 67 Watts with Power Factor (PF) 0.96 .

The machine only has 1 DIMM populated so I am wondering if the CPU is idle waiting
for access to memory. I am going to try 2 & 4 DIMM to see what difference they make.
If the LL test time improves linearly with the increased power usage, it would be worth it.

[Mark Rose]

Originally Posted by bgbeuning

A Kill-A-Watt says 67 Watts with Power Factor (PF) 0.96 .

The machine only has 1 DIMM populated so I am wondering if the CPU is idle waiting
for access to memory. I am going to try 2 & 4 DIMM to see what difference they make.
If the LL test time improves linearly with the increased power usage, it would be worth it.

You should get double the throughput. If you have four slots, make sure you use both channels.

[Madpoo]

Originally Posted by Mark Rose

You should get double the throughput. If you have four slots, make sure you use both channels.

Indeed... considering how memory intensive Prime95 is, it seems like we should encourage people to optimize their mem channels for max performance. I know it varies from system to system slightly, but if you have dual channel memory, use both channels. If you're rocking a Xeon with 3 or 4 mem channels, do that.

Optimally you'd want just one module per memory channel. I think it's the same for desktop CPU's as Xeons, where more than one module per channel will (potentially) run them at a slower speed than if you only had 1 DPC (dimm per channel).

Certain systems like the newer HP Proliants can handle running 2 or even 3 modules per channel at full speed (as long as you're using "official" HP memory, which they charge a premium price for, of course).

I have a few "unfortunate" systems where we've had to upgrade the memory in an inefficient way... they're 3-channel Xeons with support for up to 3 dimms per channel (18 slots on a dual socket board). And we've populated all 18 slots. That knocks the max speed for the DDR3 modules from 1333 MHz to 800 MHz.

Well, it works fine for the server's intended purpose, but I'm sure Prime95 runs slower as a result.

The systems in question have 144 GB of RAM... 18 x 8GB modules. If we weren't on a budget we'd have simply gone with 12 * 16GB modules for a total of 192 GB and would let it run them at 1333 or 1066 MHz (depending on the type/rank/voltage installed).

Ah well, we have to live with budgetary constraints.

[fivemack]

Originally Posted by bgbeuning

Score! I would like to hear your experiences with it. I do not see Keyboard, Video, Mouse (KVM)
connections, just Ethernet connections.

My current favorite machine is an "HP 8300 Elite" with i5-3570.
It only draw 60 Watts under full load and can do an M39,000,000 double
check in 2 weeks. A Xeon 5355 take 7 weeks.

On the other hand, an i7/4790K machine draws about 120 watts under full load and can do an M39,000,000 double-check in 36 hours.

(ah, most people are not running multi-threaded ... that explains the difference in figures)