Update: I revisit the power calculations in an addendum below.
Next-gen ultra-light laptops will be a dream come true. Lighter. Dual-core speed. Much faster solid-state disk. 75% better battery life. Combining Intel’s new Ultra Low Voltage (ULV) Core Duo processor – due this month – with the new 32GB Samsung 1.8″ flash drive will dramatically change battery life as we know it.
Laptops Are About Freedom – Not Power Cords
I used an Omnibook 300 with a 9 hour battery life for years, and loved it. I could use it for 2 or 3 days without recharging – although I didn’t have DVDs to watch. My current laptop gets about 3.5 hours, and doesn’t give the Omnibook’s wonderful sense of freedom.
Skip ahead to Feel The Power! if you don’t care where the numbers come from.
Slippery When Wet
These numbers aren’t easy to derive. A few hundred million laptops have been sold, lots of techies buy them, battery life is a problem, so its all been figured out, right? Well, maybe, but the people who know aren’t talking. Coding Horror pointed the way, but much mucking about in datasheets and trade journals was also required.
I measure in watts (W) and watt hours (Wh). Watts = volts x amps. A watt-hour is simply a one watt load for one hour. For example, a 50 Wh battery can sustain a 10 watt load for 5 hours. Since voltages and amperages vary a across batteries, processors and hard drives, watts provide a simple way to compare power usage.
Where Are We Now?
A recent Intel laptop is the new Apple MacBook. Ars Technica reports the 55Wh battery in “medium” use (iTunes streaming music, medium brightness, Wi-Fi and Bluetooth on) gets about 4.1 hours of life. Doing the math (55Wh / 4.1 hours) we get a 13.4 watt average power demand. Now we can size how the new ULV Core Duo and the Samsung 32 GB flash drive affect power consumption. Later I look at the v sexy Thinkpad X60s, where its all about the flash.
ULV Gets Down
Intel offers its processors in three power classes:
|Power Class||Core Duo Number||Core Solo Number|
|25W to 49W||T2000||T1000|
|15W to 49W||L2000||L1000|
|14W and Less (ULV)||U2000||U1000|
These power cuts aren’t free: the ULV clock (1.2GHz vs 1.83MHz) is lower and the front-side bus speed (533MHz vs 667MHz) is slower. Yet as we’ll see, the power cuts are more dramatic than these numbers would suggest.
T2400 Is Hot!
The MacBook uses the T2400. So what percentage does the processor use? The answer isn’t obvious. Intel’s SpeedStep Technology ruthlessly cuts CPU power consumption wherever it can. So Intel can give you a Core Duomaximum number (31W!) and an “Enhanced Deeper Sleep” number (3.35W). They must have their own standard workload they use for comparing processor power efficiency, but it doesn’t look like it is public.
The Process of Elimination
So we subtract the power consumption of other subsystems to estimate processor power usage. We know an idle 2.5″ 60 GB 5400 RPM hard drive consumes about 3.3W, so with some seeking call it 3.5W. Average screen brightness is another 3 watts. Bluetooth is about 0.3W. Wi-Fi power consumption depends on usage, but moderate usage is about 1W. Graphics hardware is also in the 1W range. Keeping all the other bits powered is probably about .5W. That totals to 9.3W, leaving ~4W for processor consumption in “medium” usage.
ULV U2500 Is Cool!
The newly announced U2500 is spec’d at 9.0W, or just 29% of the T2400. If the U2500 comes in at 29% of the T2500 on our MacBook, the power consumption would drop to 1.2W from 4W, for a 2.8W saving.
32-Gigabyte (GB) NAND flash-based solid state disk (SSD)
Launched in late May on an aging, time-to-market platform, this is the other big win. Using 16 of Samsung’s 16Gb NAND flash chips, this baby is not only faster
The SSD reads 300 percent faster (53MB/s) and writes 150 percent quicker (28MB/s) than normal hard drives.
it is silent, weighs about 25 grams less, and uses way less power. Let’s be conservative and say it uses .5W.
Feel The Power!
Combining 2.8W saved by the ULV Core Duo with 3W saved by the SSD, gives a 5.8W reduction. So power consumption drops from 13.4W to 7.6W. Using the same 55Wh battery, battery life goes from about 4.1 hours to 7.2 hours!
Thinkpad X60s ==> X60Super
Or take the IBM/Lenovo Thinkpad 60s, the heart throb of the Platinum Card set. With the 8 cell, 75Wh battery, the L2400 based unit tested at 7 hours battery life. Running the numbers, that is 10.7W average load. Taking off 3W for the hard drive and one watt for the ULV Core Duo, the average load drops to 6.7W and a battery life of over 11 hours!
A Jewel Of Great Price?
Engadget noted Samsung is asking about $900 (in Korea) for the new 32 GB SSD. The street price for the chips today is about $500 and prices are soft, so by the time we see them here Dell will offer them for $600. Not an impulse item, but the combination of ULV Duo’s and SSD will be catnip to road warriors.
Update:I’ve re-estimated the power and weight impact of the SSD. Take the Sony sub-3 pound TX-series laptops. Their standard battery, which they spec at 4 hours, is 58 Watt hours. Reading mail, web-surfing, and document preparation will keep your hard drive working, using – let’s be conservative – 2.5 Wh. Over four hours, that is 10 Wh or 17% of that battery’s capacity.
Samsung claims its SSD’s power consumption is 5% that of a comparable HDD, but let’s say 10% or .25 W per hour. That is 1 Wh over four hours, effectively adding nine Wh of battery capacity, or 15% – another 35 minutes of battery life. Or battery life could remain held constant and battery weight reduced by 40 grams or more. Knock another 30 grams off for the SDD and you’ve dropped almost 3 ounces. That is a lot for an ultra-portable.
thax for the info evern if you did your caculation rough it was a big help at list i have an idea now on how to calculate the battery life now tanx