Just bought an HP DM1 laptop with Intel CULV processors on a pretty nice discount. List price hovers around 450-500eur and I managed to snatch one for 350eur. The problem is that I just found out Intel has different grades of Speedstep... and one that is almost nonexistent.
This particular DM1 model I got has the Celeron SU2300 processor and there are some models with the Pentium SU4100. It doesn't start well because if you get the Celeron you have hardware virtualization extensions and the Pentium doesn't. List prices are $134 for the Celeron SU2300 and $289 for the Pentium SU4100 - given the price of laptops based on these CULV processors, I'd say Intel isn't selling either one at that price though, although the SU2300 might be closer to it. So it's $289 for a CPU with no VT-x where a cheaper processor has it - way to go for the product grading department.
Both these CPUs both support "Intel Enhanced Speedstep", which as you may know even desktop processors have now:
- Intel Celeron SU2300 @ ark.intel.com
- Intel Pentium SU4100 @ ark.intel.com
Turns out these CPUs are pretty deceiving, as the SU2300 only scales voltage slightly(around 0.1v, may vary accordingly to CPU voltage binning). The Pentium SU4100 also is similar, it only scales from 1.3GHz to 1.2GHz. I can't find the exact idle clocks for similar mobile processors but the Atoms run at 800MHz and Core 2s are similar.
There is no mention of this in ark. One can only find such specifications hidden inside the datasheet.
Since power consumption drops proportionally to the clockspeed, so pairing underclock with undervolting would yield very good results. The HP DM1 does employ C-States support, so it also saves some power there and Intel might have found it acceptable to only cut on voltage. Every bit matters and given the cost of these CPUs they sure have the margin to bin them better, especially given that the laptop isn't exactly silent, further cutting 50% would have good implications.
For proof of the actual importance of better binning, I came across another user who managed to force lower clocks through the RMClock software and brought the battery life from 4 to 7 hours in an Acer Aspire 1410, by running the CPU at around 200MHz:
Of course there's not much stopping Intel of providing even lower idle clocks like this - at an 800MHz FSB you can run the CPU at multiples of 200MHz since the bus is quad pumped.
One has to consider that the best results are obtained with this type of extreme voltage binning that is economically unfeasible but going from 4 to 6 hours would be quite possible.
I will be looking into using similar software but having to do this is disappointing for a product that is all about low power.
This is probably the last Intel CPU I'll get, where it not for the whole laptop despite this being very well built, I would be returning it right about now. There is no logical reason for doing this other than to maintain sky high profit margins.
HP has now only DM1z laptops coming out of the factory, starting at $449, running only on AMD low voltage CPUs, which thus far do have Cool'n'Quiet. Be on the lookout for 64bit FPUs on the K325 and K125, as the one with the full 128-bit FPU, the Turion II Neo K625, goes for a slight bump to $524.
You get similar battery life on the AMD processors but a better integrated GPU and possibly thermals, although I haven't put that to the test(AMD tends to leak less current even on higher process nodes, although actual power consumption is usually higher).
I will be posting my impressions of the laptop soon, but so far it seems pretty solid.
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