XP64 with 4GB+ - TTLG Forums

Duncan on 29/7/2008 at 06:32

So i've just upgraded to 4GB of RAM only to see it showing as 3.50GB. I'm sure the techheads have seen this a million times with 32bit windows, but i was under the impression that this should not happen with a 64bit OS. Is there any settings i should be changing? Or should this "just work"? What's the story here?

Rogue Keeper on 29/7/2008 at 07:55

Trivial and maybe ridiculous question, but are all modules *properly* sitting in their sockets?

Duncan on 29/7/2008 at 12:05

Yes, BIOS shows 4GB installed. And for those wondering, i do have a 64bit CPU and OS. I've seen many questions asked about this, but it seems to be from 32bit users and all replies simply say "get a 64bit OS kthxbye" (which does not help me).

Rogue Keeper on 29/7/2008 at 12:15

I used to run XP64, but only with 2GB DDRAM 1 at most. In my old P2 I had 2x 64MB modules and one 128MB module which were detected correctly as 256MB only if they were arranged in the slots in specific order : 64-128-64. But the rule of paired dimms is probably not valid by now and your issue is different, I'm not really up to date with RAM issues in era of multicore mobos (still a single core runner).

baeuchlein on 29/7/2008 at 13:04

There are several web pages available that state all sorts of things concerning 4 GB RAM, and a 64-bit OS should in theory get rid of all these problems. Unfortunately, reality differs from theory.:(

Read (http://www.brianmadden.com/content/article/The-4GB-Windows-Memory-Limit-What-does-it-really-mean-) for an explanation and some possible workarounds, (http://www.dansdata.com/askdan00015.htm) for a more in-depth explanation as well as some more switches for booting, and finally, "The 32-bit 3.2 gigabyte barrier" in (http://en.wikipedia.org/wiki/Conventional_memory#The_32-bit_3.2_gigabyte_barrier), and maybe you'll find a switch that works for you or something which explains why you're having no luck with your 64-bit OS.

Good luck! Looks like you'll need it.

Bjossi on 29/7/2008 at 16:32

God knows why Microsoft put these ridiculous artificial RAM limits.

4 GB limit on 32-bit makes perfect sense because that's the maximum amount of data that processor/OS can allocate with data registers 32-bit wide. (2^32/1024^3 = 4)

64-bit width offers 16.8 million terabytes to be allocated, 2^64 addresses, and 128-bit offers ~3000 billion billion petabytes. Although these numbers are extreme, I see no harm in allowing XP x64 to use over 4 GB when the mathematical roof is over 4.3 billion times that amount. Hell, just 16 - 24 GB would be nice for the next decade.

Rogue Keeper on 30/7/2008 at 12:03

64kb will be enough for everyone.