(I searched, couldn't find a thread on this already)

Just an FYI for you folks that haven't had the chance to install 4GB of RAM on an M90.

The M90 DOES NOT support 4GB of RAM. Sure, you can plug 4GB of RAM in, but you are only going to get 3.3GB of RAM available to whatever OS you choose to run.

When 2GB of RAM is on it, all 2GB is available to the OS. Why the 700MB loss when you go up to 4GB; I have no idea.

The other 700MB of RAM is being soaked up by the BIOS to keep the system running. Why, I have no idea.

This has been discussed to death... But, yeah, the search functionality here delivers somewhat limited results, sometimes.

Actually, it's going to be 3.25GB, if you have a 512MB graphics card. You get another quarter gig if you choose a 256MB graphics card. By the way, if you read the fine print in the order form of the M90, you'll see that they tell you that not all of the 4GB will be available...

Chipset limitation. The space is reserved for mapping memory of various devices, in particular graphics memory. Nothing that can be done about it, under any OS, 32bit or 64bit.

Rumour has it that the new Santa Rosa chipset will remove that limitation, at least for a 64bit OS.

search functionality - I look at the bottom of the page, sure enough vBulletin. LOL There is another large site I frequent with similar issues.

I have never seen a system have to reserve 1MB of system memory for every 1MB of video memory.

ok - off so search "poor chipset M90"

This is not specific to the M90. There is no current laptop model, from any manufacturer, that does not have the exact same "issue". That is because they all use the same Intel chipsets.

You don't seem to get around much, then... Seriously, though, strictly speaking the system does not "reserve 1MB of system memory for every 1MB of video memory". What it does is reserve the upper end of the address range of the 32bit system for mapping device memory, meaning that those addresses will not be available in your OS. The end result is the same, of course, if you want to see more than 3.25GB of memory, that is...

Also, you will find that many desktop machines have the same problem as well, with the possible exception of some of the most recent models, and server systems designed for handling more than 4 gigs of memory.

I get around, but Google didn't help me a whole lot.

Then I found this site and search didn't help me.

So I posted up.

My remark was strictly targeted at you saying that you had "never seen a system that etc....."

No problem at all.

Agree this been talk to death many time before, here is one of my

http://www.notebookforums.com/thread195762.html

http://www.notebookforums.com/thread194699.html

this is correct, it is not just Dell, it can be any system out there


for anyone want to know why read this
http://www.interact-sw.co.uk/iangblo...05/is3gbenough

Well 3.3 is better than 2...I am gonna go with that. What 4 gig ram did you stick into your machine? Also is the memory still running at the full 667 MHz speed in spite of 4 gig sticks being slapped in there?

Yes. Or to rephrase, any physical RAM above 3.25 Gb will be "shadowed" by other uses of the address space. So in fact, that memory will remain *completely* unused, much like older BIOSes could not see the upper end of bigger HDDs (once upon a time...).

No one has answered this so far. But if I order 4 gigs....will it still run at DDR2 667 MhZ speeds and not get slowed down?

That may be because nobody has asked...

Why would it get slowed down? If you buy 667MHz memory, it will run at 667MHz. Note, however, that there is no practical difference in speed between 533MHz memory, and 667MHz memory. The latter has higher latencies, which destroys the theoretical advantage in speed in practical applications. Synthetic benchmarks show that in many situations, the 533MHz memory is marginally faster, and sometimes the 667MHz memory wins, again by a tiny margin. In real life, you typically won't notice any difference.

What happens with 667MHz memory if downclocked to 533MHz? Will it keep the high latency, thus making it slower than regular 533MHz?

IIRC, downclocking will happen if you mix 533 and 667MHz.

I had 2 x 2GB stick directly from dell running at 677, I can't tell teh different between 533 and 677, since then I had reture 1 stick and kept one 2GB stick, my system have total 3GB now....

Short performance tests, I just can't imagine someone seeing any tangible difference between 533 and 677Mhz RAM.

So final decision for me is to get 4 gigs of RAM @ 667 Mhz. Is the Dell RAM 200 pin or 214 pin?