Spammay Blockay said:
I was just looking to buy an upgrade for my Thinkpad's processor,
and noticed that prices for Mobile Pentium 4-M chips are reasonable
until 2.5Ghz, where they jump by around $200 suddenly!
Does anyone know anything about the architecture of these chips
that would justify this massive jump in price over 100Mhz?
Price usually has more to do with supply and demand than what it costs
to do the individual parts, and there's almost always a big premium on
the top-end parts, if you want value you select one or a few steps
below the top-end parts (it's usually obvious where price chart
flattens out).
Sometimes this is caused by low yield (causing low supply and/or high
manufacturing prices), but as often it's due to market segmentation.
The Mobile Pentium 4-M only goes up to 2.6GHz, and that model isn't
even on the "Process Spec Finder"! So, I suspect that in reality the
2.5GHz CPU is the highest in that series that's really available, so
don't expect to find it cheaply until there's at least one and
possibly two MP4-M processors above it (and they have to be available
in some volume too).
Also, what is the difference between "Mobile Pentium 4" and
"Mobile Pentium 4 - M" chips? Intel seems to designate them
differently.
Different power ranges and frequency ranges (and requires different
chipsets too). The frequency range overlap somewhat, and when they do
the Mobile P4 uses a LOT more power than the Mobile P4-M for the same
performance. The Mobile P4 is basically a standard P4 with SpeedStep
support (power savings).
As an example I checked out the MP4 2.4GHz and compared it with MP4-M
2.4Ghz, "Thermal Guideline" for them are 59.8W and 35W respectively.
Quite a difference, even if Thermal Guideline doesn't tell all of the
story, the power reducing features is equally important but is much
harder to measure...
As a comparison the regular P4 2.6GHz has a Thermal Guideline around
59-60W, BUT doesn't have SpeedStep so in practice it will use
significantly more power than the Mobile P4.
The Pentium-M is much harder to compare because we can't use MHz
even as an approximation, but the 2 GHz version should certainly be
much faster and only has a Thermal Guideline of 21W...
SPEC CINT2000 suggests 1.4-1.5GHz P-M might be a more fair comparison,
there are 1.4 GHz TG at 10W(the LV version mentioned below) and 21W...
The Pentium-M 1.1GHz ULV version's TG is 5W, now THAT's low power.
Then there's Mobile Celeron (similar to Mobile P4?) and Celeron-M. It
looks C-M is P-M derived, but rumor has it that it lacks much of the
power saving features that makes P-M so effective, and the spec sheet
does indeed seem to be missing some buzzwords
The Celeron-M TG is
similar to the P-M's, but if lacks SpeedStep it's probably closer to a
MP4-M in power usage!
Intel has a lot of information all this on their Webpages, follow the
links if you want more information.
http://www.intel.com/products/notebook/processors/
This is an attempt to summarize the P-M and P4 processors commonly
used in mobile applications (the regular P4 is sometimes used for
portable "workstations", so I've included it).
Pentium-M
http://www.intel.com/products/notebook/processors/pentiumm/
* 1.3-2GHz
* Low power consumption (and the LV/ULV versions are better yet).
* 855 chipset
* Enhanced P6 derived core, significantly faster than the P4-based
cores on a per-clock basis (so MHz can't be compared directly with the
other below).
Mobile Pentium 4-M
http://www.intel.com/products/notebook/processors/pentium4-m/
* 1.4-2.6 GHz
* Medium power consumption
* Mobile 845 chipset
* P4-derived core
Mobile Pentium 4
http://www.intel.com/products/notebook/processors/mobilepentium4/
* 2.4-3.2GHz
* High power consumption
* 852 chipset
* P4-derived core
Pentium 4
http://www.intel.com/products/desktop/processors/pentium4/
* 1.3-3.6GHz
* Very high power consumption
* 925/915/875/865/848/850/845 chipset
* P4 or P4-derived core
* No SpeedStep (power/frequency management functions)