If you want to argue that PAE is treated as a value-added item and therefore
Marketing decided to "withhold" some of its functionality from Windows
clients for price differentiation purposes, go ahead. They do that stuff
all the time. That's why the Snipping Tool isn't in Vista Home Basic.
However I personally don't think there was anything like that decision
making involved with PAE.

PAE showed up around 8 years ago, if I remember correctly. Think back to
what Windows client computers were back then. A typical consumer box at
Best Buy or Comp USA was going out the door with WinME and 128mb of ram with
mobos whose memory controllers were limited to 512mb of ram. The hardware
simply didn't support any more. DDR hadn't even shown up.

By late 2001 machines were being sold with XP Home and 256mb of ram. It
cost the buyer a couple of hundred bucks to upgrade to 512mb and mobos with
three memory slots did not support anything more than 768mb. The four-slot
ones could support 2GB but 512mb memory sticks were horribly expensive and
machines usually sold with 256mb (two sticks). A few folks added more.

While all this was going on Enterprise class server boxes that could support
4+GB cost between $10k and $20k. The push for 4+GB was coming from medium
and large enterprises with large SQL and Exchange loads. Enter PAE (there
were other schemes as well). MS was not solving a general problem with PAE.
They were addressing a need expressed by enterprise users. So they
developed Windows 2000 Advanced Server and all later Enterprise server
editions to enable PAE if needed. There wasn't a need to address the issue
on the client side. So why would they?

When Intel developed the data execution bit for the later Pentium 4s in
order to support DEP it turned out that PAE could also address a conflict
sometimes encountered with DEP. That's when MS wrote PAE support into the
service packs that were releasing for W2k and XP. But only to address the
problem. Folks weren't running desktops with 4GB of memory at that time,
much less ones with more than 4GB. However, workstation users were and
that's when MS wrote XP Pro x64 to address that memory need. I don't think
MS has ever considered PAE as a suitable solution for consumers and
workstation users in addressing memory needs. There can be a perf hit with
it and I think the judgement to provide 64bit consumer operating systems
like Vista was the better choice.

"dennis" wrote in message
...
Colin Barnhorst wrote:
Where do you get the idea that MS chose not to let the clients "go
there." They inherently don't "go there." The only "choice" MS made was
to program a capability into the Windows Server editions that enables
them to "go there." The capability to enable PAE to leverage additional
addressable memory is something that has to be programmed into an OS, not
something that is programmed out of one.

Okay, again. You said it yourself: both xp and vista comes with a PAE
kernel, to support DEP.

When you enter PAE mode the CPU makes it both mathematically and
technically possible to address more than 4GB. So now the OS developer has
a *choice*. Microsoft choose *not* to support more than 4GB in the PAE
kernel (starting from XP/SP2), because there exist bad drivers out there.
*This* is what we're talking about, at least I am.