Microsoft Found to be Vista Culpable

"So what actually happens if you go out and buy 4GB of memory for your PC? Well, it's just like the DOS days - there's a hole in your memory map for the IO. (Now it's only 25% of the total address space, but it's still a big hole.) So the bottom 3GB of your memory will be available, but there's an issue with that last 1GB."

um....isn't that what i already said? ;)

oh and btw: just so everyone is clear, i contacted a Microsoft tech head, and he told me that PAE isn't utilized at all on 32-bit Windows. you may see references to the feature, but memory remapping doesn't function on 32-bit memory addresses - it's a total impossibility to remap hardware resources outside of 4GB on a 32-bit operating system regardless of the hardware that it's running on. their own KB articles do mention that too. he also confirmed that XP is no different from Vista - it's a hardware architecture limitation completely unrelated to software.

he also seconded the opinion that upgrading to more than 3GB is really a waste of money what with current memory controllers supporting differing RAM stick sizes in dual-channel mode.

he also laughed when i mentioned that the wikipedia writeup said the opposite. then i laughed too. it was loads of fun. good times.

PS: i tested a 64-bit Windows copy with appropriate hardware (P965 chipset, Core 2 Duo, 2GB RAM) and the 1MB ROM BIOS blocks still reside in the same place - in the UMA. PCI addresses from 3.125GB and higher were mapped to identical addresses, only 4GB higher (ie. starting at 7.125GB)

XP

to Clarify the memory silliness:

To address 4GB of memory you need 32 bits of address bus. (Assuming individual bytes are addressable.) This gives us a problem - the same problem that IBM faced when designing the original PC. You tend to want to have more than just memory in a computer - you need things like graphics cards and hard disks to be accessible to the computer in order for it to be able to use them. So just as the original PC had to carve up the 8086's 1MB addressing range into memory (640K) and 'other' (384K), the same problem exists today if you want to fit memory and devices into a 32-bit address range: not all of the available 4GB of address space can be given over to memory.

For a long time this wasn't a problem, because there was a whole 4GB of address space, so devices typically lurk up in the top 1GB of physical address space, leaving the bottom 3GB for memory. And 3GB should be enough for anyone, right?

So what actually happens if you go out and buy 4GB of memory for your PC? Well, it's just like the DOS days - there's a hole in your memory map for the IO. (Now it's only 25% of the total address space, but it's still a big hole.) So the bottom 3GB of your memory will be available, but there's an issue with that last 1GB.

This is getting silly people, on many motherboards you can simply enable the memory hole. It really isn't that tough and gee....poof....wallah....I see 4GB memory....ummm but this is just on my XP Media Center....I dumped my Vista machine so can't vouch that it would work there.....ugly stuff...

Mozilla,

Wiki can indeed be edited by anyone...and it is a remarkable resource. So what is the big deal? There is a load of info and dis-info available from various resources. Assuming one over the other is the almighty truth is a bit remiss.

Thanks for the detail StarWhite...some of us here really do understand this so there is hope...