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64-bit execution helps to speed up encryption and decryption as
well as file compression.<br>
This aids in archiving, secure shells, secure sockets, and memory
to memory copy,<br>
not to mention compiler (gnu) and linker (ld) speed-ups.<br>
<br>
There are also hardware considerations besides memory size, such
as multi- channel<br>
memory configuration and use of matched memory sticks. Upgrading
to 64-bit can <br>
get an even better throughput increase if all the hardware and
BIOS factors are in accord.<br>
<br>
If your computer is using all available memory and a significant
portion of swap space, then<br>
you have a situation known as "running from the disk". If that
is case, your system will be<br>
rather pokey and the remedy is to add more memory. This can
happen regardless of whether<br>
you are running a 32-bit kernel or a 64-bit kernel. <br>
<br>
<br>
On 05/31/2013 02:08 PM, Lisa Kachold wrote:<br>
</div>
<blockquote
cite="mid:CAEYqmRtn3ZMvQOQWzo6kvt86ZDvBVi782sZR3EB91pu_Jp_-vw@mail.gmail.com"
type="cite">Hi Keith,
<div><br>
</div>
<div>Excellent subject! See my inline comments below:<br>
<br>
<div class="gmail_quote">On Fri, May 31, 2013 at 9:28 AM, keith
smith <span dir="ltr"><<a moz-do-not-send="true"
href="mailto:klsmith2020@yahoo.com" target="_blank">klsmith2020@yahoo.com</a>></span>
wrote:<br>
<blockquote class="gmail_quote" style="margin:0 0 0
.8ex;border-left:1px #ccc solid;padding-left:1ex">
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<td style="font:inherit" valign="top"><br>
Hi,<br>
<br>
Even though I have 64bit hardware I always install
the 32bit version of Linux. I do so because of the
past discussions on this list that made me believe
the 32bit OS was better because 64bit caching is
actually slower due to the requirement that the
cache be filled to a certain point before it is
moved. I think I recall something about the amount
of RAM having some effect here also. <br>
</td>
</tr>
</tbody>
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</blockquote>
<div><br>
</div>
<div>The full questions of whether to use 64 bit OS verses 32
bit are included below. For instance with a Python based
application, CPU performance gains (possible 10%) verses
greater memory requirements (30%) (in 64bit OS).</div>
<div><br>
</div>
<div>It is really going to depend on what the server is doing?
Is that application actually optimized for 64 bit
registers? </div>
<div><br
style="color:rgb(51,51,51);font-family:Verdana,Arial,Tahoma,Calibri,Geneva,sans-serif;font-size:13px;background-color:rgb(243,243,243)">
</div>
<div>Reference: <a moz-do-not-send="true"
href="http://askubuntu.com/questions/7034/what-is-the-difference-between-32-bit-and-64-bit-and-which-should-i-choose">http://askubuntu.com/questions/7034/what-is-the-difference-between-32-bit-and-64-bit-and-which-should-i-choose</a></div>
<div><br>
</div>
<div>If you are running a database application, with more than
4 GB RAM, you might find great speed improvement with
memcached under 64bit. </div>
<div><br>
</div>
<div>
<div class="post-text" style="margin:0px 5px 5px
0px;padding:0px;border:0px;font-size:14px;vertical-align:baseline;width:660px;line-height:18px;font-family:Arial,'Liberation
Sans','DejaVu Sans',sans-serif">
<p style="background-color:transparent;margin:0px 0px
1em;padding:0px;border:0px;font-size:14px;vertical-align:baseline;clear:both;word-wrap:break-word"><strong
style="margin:0px;padding:0px;border:0px;font-size:14px;vertical-align:baseline;background-color:transparent">From
a technical perspective, a 64-bit OS gives you:</strong></p>
<ul style="margin:0px 0px 1em
30px;padding:0px;border:0px;font-size:14px;vertical-align:baseline;list-style-position:initial">
<li
style="background-color:transparent;margin:0px;padding:0px;border:0px;font-size:14px;vertical-align:baseline;word-wrap:break-word">
<p style="margin:0px 0px
1em;padding:0px;border:0px;font-size:14px;vertical-align:baseline;background-color:transparent;clear:both;word-wrap:break-word;background-repeat:initial
initial">Allows individual processes to address more
than 4 GB of RAM each (in practice, most but not all
32-bit OSes also limit the total usable system RAM
to less than 4 GB, not just the per-application
maximum). While a PAE kernel also does this; it is
significantly slower!</p>
</li>
<li
style="margin:0px;padding:0px;border:0px;font-size:14px;vertical-align:baseline;word-wrap:break-word">
<p style="margin:0px 0px
1em;padding:0px;border:0px;font-size:14px;vertical-align:baseline;clear:both;word-wrap:break-word"><span
style="background-color:rgb(255,255,255)"><font
color="#ff0000">All pointers take 8 bytes
instead of 4 bytes. The effect on RAM usage is
minimal (because you're not likely to have an
application filled with gigabytes of pointers),
but in the worst theoretical case, this can make
the CPU cache be able to hold 1/2 as many
pointers (making it be effectively 1/2 the
size). For most applications, this is not a huge
deal</font></span><span
style="color:rgb(255,255,255);background-color:rgb(255,0,0)">l.</span></p>
</li>
<li
style="background-color:transparent;margin:0px;padding:0px;border:0px;font-size:14px;vertical-align:baseline;word-wrap:break-word">
<p style="margin:0px 0px
1em;padding:0px;border:0px;font-size:14px;vertical-align:baseline;background-color:transparent;clear:both;word-wrap:break-word;background-repeat:initial
initial">
There are many more general-purpose CPU registers in
64-bit mode. Registers are the fastest memory in
your entire system. There are only 8 in 32-bit mode
and 16 general purpose registers in 64-bit mode. In
scientific computing applications I've written, I've
seen up to a 30% performance boost by recompiling in
64-bit mode (my application could really use the
extra registers).</p>
</li>
<li
style="background-color:transparent;margin:0px;padding:0px;border:0px;font-size:14px;vertical-align:baseline;word-wrap:break-word">
<p style="margin:0px 0px
1em;padding:0px;border:0px;font-size:14px;vertical-align:baseline;background-color:transparent;clear:both;word-wrap:break-word;background-repeat:initial
initial">
Most 32-bit OSes really only let individual
applications use 2 GB of RAM, even if you have 4 GB
installed. This is because the other 2 GB of address
space is reserved for sharing data between
applications, with the OS, and for communicating
with drivers. Windows and Linux will let you adjust
this tradeoff to be 3 GB for applications and 1 GB
shared, but this can cause problems for some
applications that don't expect the change. I'm also
guessing it might cripple a graphics card that has 1
GB of RAM (but I'm not sure). A 64-bit OS can give
individual 32-bit applications closer to the full 4
GB to play with.</p>
</li>
</ul>
<p style="background-color:transparent;margin:0px 0px
1em;padding:0px;border:0px;font-size:14px;vertical-align:baseline;clear:both;word-wrap:break-word"><strong
style="margin:0px;padding:0px;border:0px;font-size:14px;vertical-align:baseline;background-color:transparent">From
a user's perspective:</strong></p>
<ul style="background-color:transparent;margin:0px 0px 1em
30px;padding:0px;border:0px;font-size:14px;vertical-align:baseline;list-style-position:initial">
<li
style="margin:0px;padding:0px;border:0px;font-size:14px;vertical-align:baseline;background-color:transparent;word-wrap:break-word;background-repeat:initial
initial">
<p style="margin:0px 0px
1em;padding:0px;border:0px;font-size:14px;vertical-align:baseline;background-color:transparent;clear:both;word-wrap:break-word;background-repeat:initial
initial">Application speed is usually faster for a
64-bit application in a 64-bit OS compared to the
32-bit version of the application on a 32-bit OS,
but most users won't see this speed-up. Most
applications for normal users don't really take
advantage of the extra registers or the benefits are
balanced out by bigger pointers filling up the
cache.</p>
</li>
<li
style="margin:0px;padding:0px;border:0px;font-size:14px;vertical-align:baseline;background-color:transparent;word-wrap:break-word;background-repeat:initial
initial">
<p style="margin:0px 0px
1em;padding:0px;border:0px;font-size:14px;vertical-align:baseline;background-color:transparent;clear:both;word-wrap:break-word;background-repeat:initial
initial">
If you have any memory hog applications (like photo
editors, video processing, scientific computing,
etc.), if you have (or can buy) more than 3 GB of
RAM, and you can get a 64-bit version of the
application, the choice is easy: use the 64-bit OS.</p>
</li>
<li
style="margin:0px;padding:0px;border:0px;font-size:14px;vertical-align:baseline;background-color:transparent;word-wrap:break-word;background-repeat:initial
initial">
<p style="margin:0px 0px
1em;padding:0px;border:0px;font-size:14px;vertical-align:baseline;background-color:transparent;clear:both;word-wrap:break-word;background-repeat:initial
initial">
Some hardware doesn't have 64-bit drivers. Check
your motherboard, all plug-in cards, and all USB
devices before making the switch. Note that in the
early days of Windows Vista, there were lots of
problems with drivers. These days things are
generally better. nVidia for instance is one of the
drivers optimized for 64bit which is extremely
faster.</p>
</li>
<li
style="margin:0px;padding:0px;border:0px;font-size:14px;vertical-align:baseline;background-color:transparent;word-wrap:break-word;background-repeat:initial
initial">
<p style="margin:0px 0px
1em;padding:0px;border:0px;font-size:14px;vertical-align:baseline;background-color:transparent;clear:both;word-wrap:break-word;background-repeat:initial
initial">
If you run so many applications at a time that
you're running out of RAM (usually you can tell this
because your computer starts getting really slow and
you hear the hard disk drive crunching - indicating
your caching), then you'll want a 64-bit OS (and
sufficient RAM).</p>
</li>
<li
style="margin:0px;padding:0px;border:0px;font-size:14px;vertical-align:baseline;background-color:transparent;word-wrap:break-word;background-repeat:initial
initial">
<p style="margin:0px 0px
1em;padding:0px;border:0px;font-size:14px;vertical-align:baseline;background-color:transparent;clear:both;word-wrap:break-word;background-repeat:initial
initial">
You can run 32-bit applications (but not drivers) in
64-bit land with no problems. The worst slowdown
I've measured for a 32-bit application in 64-bit
Windows is about 5% (meaning that if it took 60
seconds to do something in 32-bit, it took at most
60/0.95 = 63 seconds with the same 32-bit
application in 64-bit).</p>
<p style="margin:0px 0px
1em;padding:0px;border:0px;font-size:14px;vertical-align:baseline;background-color:transparent;clear:both;word-wrap:break-word;background-repeat:initial
initial"><br>
</p>
<p style="margin:0px 0px
1em;padding:0px;border:0px;font-size:14px;vertical-align:baseline;background-color:transparent;clear:both;word-wrap:break-word;background-repeat:initial
initial">
All in all, personally, Keith, I would install 64bit
CentOs 6 unless you have a better reason not to?</p>
<div><br>
</div>
</li>
</ul>
</div>
</div>
<blockquote class="gmail_quote" style="margin:0 0 0
.8ex;border-left:1px #ccc solid;padding-left:1ex">
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<tbody>
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<td style="font:inherit" valign="top"><br>
Using a 32bit version over a 64bit version seems
counter intuitive, however that is what I have taken
away from these conversations about 32bit vs 64bit
Linux. <br>
<br>
I'm using CentOS 6.x on a LAMP server that gets a
low amount of traffic. However I may make the jump
to Linux on my desktop this summer. (this will be my
3rd attempt to become M$ free except one VM so I can
use IE for testing) I think all of my hardware is
64bit. <br>
<br>
So that begs the question, is 32bit better than
64bit or do I not understand the issue?<br>
</td>
</tr>
</tbody>
</table>
</blockquote>
<div><br>
</div>
<div>The issue is complex, but now in this new moment of time,
a greater number of drivers are optimized for 64 bit
registers.</div>
<div> </div>
<blockquote class="gmail_quote" style="margin:0 0 0
.8ex;border-left:1px #ccc solid;padding-left:1ex">
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<tbody>
<tr>
<td style="font:inherit" valign="top"><br>
Thank you for your feedback.<br>
<br>
Keith<br>
<br>
------------------------<br>
Keith Smith</td>
</tr>
</tbody>
</table>
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