Three out of Four Isn't Bad

[Roger Heflin]

Bill Davidsen wrote:
> Langdon Stevenson wrote:
>> Roger Heflin wrote:
>>> Néstor wrote:
>>>> I have a situation where I have 36 Gigs of ram on a machine and I 
>>>> could only
>>>> see 4 Gigs
>>>> then I installed the PAE kernel and I can only see 24 Gigs.  I have 
>>>> a ticket
>>>> opened with
>>>> Red Hat to see what they recommend.
>>>>
>>>> :-)
>>>>
>>>
>>> If that is a 64-bit capable machine, you should run 64-bit on it, you 
>>> can run 32-bit userspace stuff, but if you run a 32-bit os with that 
>>> kind of ram you run into all sorts of issues with the machine running 
>>> out of the 800-900MB of lowmem and this causes fatal issues even 
>>> those massive amounts of highmem are available.   You will have 
>>> enough issues with 32-bit and lots of ram to make it worth 
>>> considering the 64-bit stuff.
>>>
>>>                               Roger
>>
>>
>> I recently upgraded from F7 to F8 and went with the 32 bit F8 version 
>> rather than the 64 F7 due to the significant difficulties I had with 
>> FireFox/Flash/Java.
>>
>> I had installed another 2 Gig of RAM just prior to the upgrade and it 
>> showed up fine under F7 64bit.
>>
>> However on F8 32bit I can only see 3.2 gig of my RAM.  It is not a 
>> huge problem as I don't use it all.  The 64 version of F7 used to 
>> gobble up all of my RAM occasionally (I could never figure out why, or 
>> what application was responsible).  That problem vanished with the 32 
>> bit F8 and 32 bit apps.
>>
>> It is interesting though that when the 64 v's 32 bit question has been 
>> asked on this list that I have never heard this memory limit mentioned 
>> (I may have missed it though).  Perhaps it is just that RAM is now 
>> soooooo cheap that it is only just becoming an issue.
>>
>> Still.  Looks like a really good reason to go with 64 bit next time I 
>> do an upgrade!
>>
> I didn't get all my RAM even with 64 bit, so don't bet the farm on it 
> working.
> 

The problem is the MB maker has 2 choices:

Maximize the amount of ram below the 4GB line and waste .5-.75 GB of ram and 
maximize the amount of ram usable for 32-bit windows, OR

Maximize the total amount of ram for 64-bit, but make 32-bit windows potentially 
see 1-2GB of ram less (this one is never chose because most run 32-bit windows)

And/OR put in an option to select between Linux and windows, usually this was 
done on the high-end dual socket boards (but not on the dual-socket desktop type 
boards), I don't think it was ever done on any of the single socket stuff.

And often on the high end boards there is also someplace a memory-mapping option 
of (none,software,hardware), and each of the 3 different options can show 
different amount of ram, and each of the 3 can make a fair difference in 
performance (one MB choosing one over the other make a 5% diff in specFP results).

                           Roger