PAE causing system crashes

[Michael Barnett]

I have 3 dell machines with 2x xeon procs, 8G of ram, and a half  
terabyte raid 5.  I attempted to run the AMD64 distribution on these  
boxes which was fine for everything except mysql, (which is all these  
boxes are going to do) so I reinstalled 5.4 i386.

uname -a  looks like (hostname obscured):

FreeBSD myhost.mydomain.com 5.4-RELEASE-p9 FreeBSD 5.4-RELEASE-p9 #2:  
Mon Jan 16 23:27:12 PST 2006     root at myhost.mydomain.com:/usr/obj/ 
usr/src/sys/SMP-PAE  i386


My problem is, if i don't enable PAE in the kernel, i can only  
address half the ram in the boxes, but... the machines are stable.

If i do enable PAE, i can address all the memory, but they randomly  
reboot without dumping any errors or logging.

To enable PAE, i am building and booting off the following kernel  
config:

<snip>
include PAE

ident           SMP-PAE

options         SMP
options         KVA_PAGES=512
</snip>

I added the KVA_PAGES options hoping to stabilize the machine  
(doesn't seem to have made any difference.)  The only other tuning i  
am doing at the moment is in loader.conf:

<snip>
kern.maxdsiz="2147483648"                # Set the max data size
</snip>

When i boot without PAE I use the generic SMP kernel, and the machine  
is stable.

I know that there are a number of other kernel tunables i could be  
tweaking, but I am not really sure where to start as the machine dies  
silently.  I was hoping that someone who has run a stable PAE kernel  
with 8G of ram + could point me in the right direction.

Thanks,

-Michael