# Morning Discussion: Holiday Edition

by Alice O'Connor, May 31, 2010 5:00am PDT

Today is a holiday in both the USA and the UK--Spring Bank Holiday in the UK and Memorial Day in the USA--so we'll be running a little light on coverage but rest assured, we will have a few things to help you avoid working. Everywhere else, we apologise.

Like zombies? 'drMikey' sends word that he is selling prints of the acrylic painting that won him an honourable mention in our recent Left 4 Dead art contest. Brain-tastic.

• dumb battery backup/power supply question - if I've got a 750W power supply on my PC, do I actually need a 750W+ UPS unit?

I basically just need something to keep stuff from being fried if the power goes on and off real quick. Don't need it to run the PC for an hour.

Thread Truncated. Click to see all 8 replies.

• Quick electronics lesson: (tl;dr: get a Kill-A-Watt, buy a UPS that matches the power you consume)

This isn't necisarrily aimed at you, just for anyone who didn't already know. Power is measured in Watts. It's how much energy moves between two bodies in the course of 1 second. Power = (Voltage * Current) / sqrt(2). Your voltage is (or at least should be) stuck at 120 volts. This means your power directly relies on your current (amps) which will vary depending on what you're asking your machine to do (how many drive motors you have spinning, how many transistors you're switching at a given time, etc).

The Power ("Wattage") on your PSU is the maximum amount of power the device is designed to dish out without something going wrong inside it. The only reliable way to know how much power your machine is actually using is by measuring it. I suggest a Kill-A-Watt (just google it). The "Wattage" on the UPS is likewise how much power it will dish out. I had an old 300 watt UPS that would suddenly kill all power to my pc in the middle of games because I would pull more than 300 watts. The UPS will also have a second rating that will show how much time the battery will last at various given powers (eg 30 mins @ 300 W).

The power rating, and the battery time are in-and-of themselves independent. However, you will find that a UPS with a higher power rating will come with a larger battery.