Three out of Four Isn't Bad
Roger Heflin
rogerheflin at gmail.com
Sat Apr 19 20:53:48 UTC 2008
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
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