Memory speed

Most of the Pentium-M laptops I look at have a 400Mhz FSB yet use DDR333 SODIMM memory. Why aren't these using DDR400(PC3200) memory ?

One of the moderators suggested that you could insert faster memory but it won't run any faster. Can anyone verify that ? It sounds very wrong.

On desktops the BIOS reads the serial SPD register of the memory then places the timing info into the memory controller chip ... 845, 875 whatever. Why is this any different on a laptop & i855 ?

 

That is right, inserting faster (DDR 400) memory will serve no benifit, in fact it could make things worse as a number of people have reported serious stability issues when too faster speed ram is installed.
There will be an upgrade to 533FSB when intel release their next verison of the PM and a new chipset to go with it, possibly late this year/early next year. You'll get faster RAM then.
a

 

Sure the BIOS reads the SPD, but still the 855 chipset is only spec'd to work with PC2100 and PC2700 memory. If you really trust the memory makers' claims that their PC3200 memory is PC2700-compatible, then I guess it's worth a try, but I've also seen reports that PC3200 fails in various Centrino machines. Given the difference in price, probably no one has felt like sacrificing to test the theory. And the transition from PC2100 to PC2700 wasn't necessarily painless either; the spec called for shorter traces to the memory modules to support the higher speed and some Centrino motherboards had to be redesigned to meet the new timing requirements. So to expect that you can drop faster memory in and have the chipset take advantage of it automatically is probably wishful thinking.

By the way, one of my pair of 1GB PC2700 Kingmax SODIMMs died a few days ago, and I need to exchange it for a new one. I ran a few hours worth of tests on the remaining module and it hasn't croaked, so hopefully the other failure was a fluke.

old: Sony PCG-GR300P 1.13GHz PIII-M, 512MB
new: Asus M6Ne 2.00GHz P-M, 2GB

 

Hm, some updates just for completeness -

I tried installing Kingmax PC3200 memory in my M6Ne, and it refused to power up.

I noticed that Geared2Play.com bundles DDR400 memory with all their M6's, so I ordered a couple sticks of those and just got to try them out tonight. They boot up fine, but they come up with the exact same CAS latency settings as my Kingmax DDR333 memory. And of course, the M6 BIOS doesn't have memory settings in any of its menus.

But I managed to use WPCREDIT along with the Intel 82855 Data Sheet to manually reset my timings. I'm now running the DDR400 memory, still at 333MHz, but with 2-2-2-5 timing instead of the default 2.5-3-3-7, and the system is measurably faster.


old: Sony PCG-GR300P 1.13GHz PIII-M, 512MB
new: Asus M6Ne 2.00GHz P-M, 2GB

 

Great note Highlandsun - and it's greatly appreciated.
What memory did you get from geared2play.com ? Got a
brand or the memctl interface chip ?

 

There's no name on the label at all. I guess you can email geared2play.com for the details.

Here's what I can read from the module label:

512MB DDR-400MHz-CL2.5
PC3200S-25330 3-3071601

Plus the usual - Made in Taiwan, warranty void if removed...

Aside from the memory chips themselves, the only other thing I can recognize is the SPD eeprom.

The system actually ran even with CL=1.5, I'm impressed. I haven't found the stable limit yet, there are a number of parameters to play with and decreasing some timings in combination with others can slow down performance instead of speeding up (if it doesn't just crash outright).

old: Sony PCG-GR300P 1.13GHz PIII-M, 512MB
new: Asus M6Ne 2.00GHz P-M, 2GB

 

For future reference, I've written up how to change the memory timings on my web page here: http://highlandsun.com/hyc/centrino/

Hope it helps someone.

old: Sony PCG-GR300P 1.13GHz PIII-M, 512MB
new: Asus M6Ne 2.00GHz P-M, 2GB

 

<blockquote id='quote'> quote:<hr height='1' noshade id='quote'>Originally posted by highlandsun

 

OMG!!!

i am blind as a bat!

just now read where you have already posted directions on your website... please excuse my oversight and a HUGE THANK YOU for sharing your experience!

rtb

 

You're welcome. Post any interesting results you get here, I'm curious to see what other folks are doing...

old: Sony PCG-GR300P 1.13GHz PIII-M, 512MB
new: Asus M6Ne 2.00GHz P-M, 2GB

 

Highlandsun:

Great info in your site, shure i would like to set fastest timmings in my acer.

I have follow the guide but in the end no changes at all.

I have centrino 1.5Ghz with i855GME chipset.

Did you use cpuz to check the change in timmings?

 

The i855GM/GME has a different register layout than the i855PM. You'll have to look up the Intel Datasheets to find out how to set the timings there.


old: Sony PCG-GR300P 1.13GHz PIII-M, 512MB
new: Asus M6Ne 2.00GHz P-M, 2GB

 

Already tryed that but still no go, cpuz shows same timmings al the time

 

<blockquote id='quote'> quote:<hr height='1' noshade id='quote'>Originally posted by nights