Do slower processors give longer battery life?

Do slower processors give longer battery life? How much of an effect?

I'm looking to get a Studio and wonder whether I should consider a slower processor for that reason. If it bogs down under Vista, however, that's not good.

I want to get the 9-cell battery.

 

slower processors will add on a little battery life, but low voltage processors give the best amount. i would suggest getting the integrated video as opposed to the ATI video card for more power savings.

 

Depends. If you've got a Pentium 4, it'll be slower and consume more power than a P8400, but if you've got an Atom, it'll be slower and consume less power than a P8400.

 

Actually i think you are better off getting a faster one. Why? because the cpu will be on load for less time. It is really only when they are loaded that they consume power. If a fast one can do the task in 1 sec vs 2 secs of a slow one well you have added a good amount of battery life. Get the idea?

This of course is only good to compare against exact same lines of processors. Going from a 5xxx series to a 8xxx series can not be comparable. Get the one with the lowest voltage as others said. It should give you the best results - but slower does not mean more battery.

 

I don't think it works that way, because a faster processor also burns more power while it is computing. That's why we didn't need elaborate cooling systems 19 years ago when I bought my first PC... processors were slower then. I believe that the power consumed is actually proportional to the amount of computing done... I think that "information theory" demonstrates that. What's of more significance is the power it burns while it is "idling," because it spends most of its time idling. As you point out, the voltage is probably more significant.

 

Well the power used idling is much much lower than when in use. This is greatly enhanced with the addition of speedstep several years ago.

If they have the same TDP (thermal design power) which they should if they are from the same line (you can compare the 2 processors on intels website) then technically they should use the same power at idle and the same power at load. Like i said before, the faster processor will be at load shorter allowing it to go in its lower power sleep states with the speedstep faster.

The differences here that were looking at are very small for general websurfing/mp3 listening when on battery though. I would doubt the difference would be more than a few minutes at most.

 

Of course, but I'm talking about comparing the "idle power level" from processor to processor, which, even if similar, is bound to be different slightly.

I'm not an expert at this, but I believe that the power consumed (in addition to the background or idle power) is proportional to the number of bits flipped inside the processor as it does its job. The faster and slower processors both need to flip the same number of bits. Hence they will use the same power for doing the computation (although one must account for other differences in efficiency). Assuming they have the same basic process, differences in power consumption probably come more from differences in the idle power, which may (may) be larger in the faster processor.

 

In theory, this is true. In theory, if a P8400 and a P9500 have the exact same power draw at idle and load, the P9500 will not only complete a task faster, but using less energy as well. In practice, though, I'm willing to bet that the P9500 actually draws a bit more power at idle and load, negating some, if not all of the savings gained through faster completion of the task at hand.

 

All processors will clock down to ½ or less their rated speed when idling. Therefore the maximum clock speed of the processor will have a very little impact on overall power consumption, especially when idling and doing light work. I don’t think there is a significant difference between two processors built on the same technology with different clock speeds. If you are comparing two different generations then there can be a difference.

 

When I try to order a Studio 15 from the Dell website, I tried to choose both a P series processor and integrated video, and it won't let me. The only model that offers a P series processor forces you to get the ATI video. The only models that use integrated video don't offer a P processor. Any idea which is the more significant effect? I'm guessing the P processor matters more. It saves 10 w. That's huge.

 

Trying calling them.

It might just be the site being dumb, but it may be that they've actually got two different motherboards in the Studio 15 - an older, integrated GPU board with a 965 chipset and a newer, dedicated GPU board with a 45 chipset. Since the P8x00 and P9x00 processors don't work on the 965, Dell can only offer them on the dedicated GPU variants.

The nominal difference in TDP between T-Series and P-Series processors may be 10W, but in practice this figure probably varies greatly. Furthermore, the nominal 10W difference suggests that the processor is running at full load, which, as mentioned, is only rarely the case.

Despite being fabricated on a last-generation process, due to their relatively low clock speeds and small caches, some of the low-end T-Series processors like the Pentium Dual-Cores may effectively have power requirements similar to those of their younger P-Series cousins.

In general, though, if you're into power-savings, I'd go look for something with a genuine P-Series processor rather than take a crapshot at my theory. Then again, I've never seen what people see in the Studio, so to each his own.

 

Yes, I need to talk them directly. I was aware of this at 1:00 am last night.. I urgently needed to talk and THEY HAVE NO WAY TO REACH A HUMAN AT 1:00 AM! What kinds of deviants are these people?

If the 10 w comes from running at foll load, then in reality the difference is much smaller, maybe 5% or less. The only issue is this: sometimes I use the laptop to "render" computed music which can take 100% cpu (or 50% in a dual core system) for several minutes. I would love to be able to make several renders like this while I'm working, and that will burn battery energy at the maximum rate possible.

Lacking any other info, I'll probably go with a P processor. Which leads me back to wondering they will give me integrate video with that.

Mike

 

Lol, terrible ain't it?

If you're actually more worried about full-load power draw, you could get a T-Series chip and undervolt it. You usually can't tweak idle voltages on Intel chips, but there's often a good deal of headroom at load. There's a great guide floating around somewhere.

I say that as you're probably going to have to wait for a Studio refresh before any progress is made on this front - assuming that the motherboard is the problem. Else it still might be a call away.

 

Does the BIOS in the Studio permit that kind of tweaking of voltages, then?

I don't follow your last paragraph.

thanks,
Mike

 

The BIOS in the Studio won't let you touch the processor. You have to use rmclock as illustrated here.

In the last paragraph I meant to say that if the above theory is true, Dell is unlikely to give you a P-Series processor and an IGP in the Studio 15. You will have to wait until they come out with a replacement for said laptop. If the above theory is not true, you can probably get a P-Series processor and an IGP by configuring the machine over the phone.

 

I had this same Dilema my self do I get a P8400 with 3MB cache and a power useage of 25TDP or a T9400 6MB cache and 35watt TDP.


In the end I opted for the T9400 the 6MB cache make up for the extra 10 watts of power I use but in the end it balances out because the CPU is faster has more Cache so it has to work less.

 

Faster processors of the same TYPE will use more power. Generally newer classes of processors are probably more energy efficient at similar speeds, because they are engineered that way. A "P" processor at 2.4GHz will use less power than a "T" processor at the same speed, but might use more power than a "T" processor at 1.8GHz. And then there are the "low voltage" processors, "SU" I think.

I have an old Inspiron 8600 with a 1.4GHz Pentium, and a new Latitude E6500 with a P9500 2.5GHz processor. I seem to get similar battery life out of the 2, but the new one is a little more than 3 times as fast as the old one.

 

I'm sure that I read somewhere that the newest T penryn processors are extremely similar to the newest penryn P processors apart from the FSB. i.e. the t8300 will have a extremely similar power consumption(i.e. negligeble difference) as the p8600 due to the fact that TDP is a figure for the maximum and doesn't tell you how much battery the CPU actually uses. But obviously it's best to go for newer CPU's as these will probably have newer motherboards etc which is good when/if you wish to upgrade.