<p dir="ltr">The best explanation of hyperthreading in reasonable terms has been this one. </p>
<p dir="ltr"><a href="http://www.tomshardware.com/answers/id-1694436/hyperthreading-work.html">http://www.tomshardware.com/answers/id-1694436/hyperthreading-work.html</a></p>
<div class="gmail_extra"><br><div class="gmail_quote">On Sep 6, 2016 7:48 PM, "Tom Jones" <<a href="mailto:tomjones@centurylink.net">tomjones@centurylink.net</a>> wrote:<br type="attribution"><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><div><div style="font-family:times new roman,new york,times,serif;font-size:12pt;color:#000000">I have to answer these sorts of questions at work from time to time. Hyperthreading, for some reason, really throws people for a loop, no pun intended.<br><br>Each "core" on a modern processor chip is, or would be if we could separate them, a CPU in it's own right. So if you have a four core CPU, that's actually four physical processors on a single chunk of silicon.<br><br>Hyper-threading is done within a given core to make it appear as two cores. More or less it's a way to stuff the chip's execution pipelines so that two threads are interlaced and the CPU utilization is higher than when running a single thread. I'm sure someone on the list could come up with a better analogy, but that's all I got right now. Enabling hyperthreading is usually done at the BIOS level. To the OS it appears as two cores. So a four core processor with hyperthreading enabled will look like an eight core processor to the OS.<br><br>At no time does the CPU divide itself from 64 to 32 bit subunits. If it is a 64 bit CPU with hyperthreading turned off, then it is a 64 bit CPU with hyperthreading turned on. Whether your programs are running as 64 or 32 bit will depend mostly on how they're compiled.<br><br><hr><div style="color:#000;font-weight:normal;font-style:normal;text-decoration:none;font-family:Helvetica,Arial,sans-serif;font-size:12pt"><b>From: </b>"David Schwartz" <<a href="mailto:newsletters@thetoolwiz.com" target="_blank">newsletters@thetoolwiz.com</a>><br><b>To: </b>"Main PLUG discussion list" <<a href="mailto:plug-discuss@lists.phxlinux.org" target="_blank">plug-discuss@lists.phxlinux.<wbr>org</a>><br><b>Sent: </b>Tuesday, September 6, 2016 4:29:59 PM<br><b>Subject: </b>Re: 4 cores and 8 threads<br><br>
<p>AFAIK, the “cores” are 64-bit ALUs that can split into 32-bit pairs to run 32-bit code.</p>
<p>So an i7 has four x 64-bit cores that also work as 8×32-bit CPUs.</p>
<p>Threads are an OS construct, unless you want to refer to them as “real” vs. “virtual”, in which case you’d have up to four 64-bit threads or eight 32-bit threads.</p>
<p>I run VMWare, and I’ve never really bothered to figure out how it does its CPU mapping. I think I’ve given it two cores and 2GB of RAM and it does fine running Win 7.</p>
<p>(My base system is a Mac with a 2.8 GHz i7, 16 GB of RAM, and the latest OS X.)</p>
<p>-David Schwartz</p>
<blockquote><p>On Sep 6, 2016, at 3:53 PM, Keith Smith <<a href="mailto:techlists@phpcoderusa.com" target="_blank">techlists@phpcoderusa.com</a>> wrote:</p>
<p>Hi,</p>
<p>If an Intel CPU has 4 cores and 8 threads will it look like 8 cores to VirtualBox when assigning resources to a guest?</p>
<p>If so is there a way to determine which is a tread and which is actually a core?</p>
<p>Thanks!! Keith ------------------------------<wbr>--------------------- PLUG-discuss mailing list – <a href="mailto:PLUG-discuss@lists.phxlinux.org" target="_blank">PLUG-discuss@lists.phxlinux.<wbr>org</a> To subscribe, unsubscribe, or to change your mail settings: <a href="https://u2206659.ct.sendgrid.net/wf/click?upn=5DvWGaZUY8Sh5aRLWfQTKYiRLVzunonVk948p8WIzMe-2FXlJ9Cta8w8U9xoku9LrUSHNMJbSd3ZEwH-2BqnW2UHlA-3D-3D_6lpMB7VLnN-2Fj9-2FEErg8-2F-2BMBpb5QxlByTgv2M3fbWD9ebvC-2BWrN3h7jImK8EVWYBeRqz5uVuARR77-2FXYCoX3CyRZ-2F-2BqJUzThg-2FqaFqN9RxtdgpBGhguDbaZb0CTQQl9jvOTJtewZlDe1mrHkjqvQllVXF4pcJ-2F-2FDS3K2jeXqdbfaPYwgo-2B3xhpLFMYYBGINjiYQhbC6eHGfoETTUh6RMyUx8TTdi233xHex4Fyo2LePY-3D" target="_blank">http://lists.phxlinux.org/<wbr>mailman/listinfo/plug-discuss</a></p></blockquote>
<img alt="" style="min-height:1px!important;width:1px!important;border-width:0!important;margin-top:0!important;margin-bottom:0!important;margin-right:0!important;margin-left:0!important;padding-top:0!important;padding-bottom:0!important;padding-right:0!important;padding-left:0!important" src="https://u2206659.ct.sendgrid.net/wf/open?upn=6lpMB7VLnN-2Fj9-2FEErg8-2F-2BMBpb5QxlByTgv2M3fbWD9ebvC-2BWrN3h7jImK8EVWYBeRqz5uVuARR77-2FXYCoX3CyVl3ALBTJ-2BDtZ5M7MNhJa82UjkcD2CsUafwIAm3VjhOBQ-2Fa-2FZxdRwc9C-2BdQfmtArBTxirHCPtGzQP2CiK2da3FYOZcttAMAwr41GlsIhZjO-2B3LCzgRVPvYWuzPGseVNXnG41VPjABgLNj-2Bi3z2vLpKk-3D" height="1" width="1" border="0">
<br>------------------------------<wbr>---------------------<br>PLUG-discuss mailing list - <a href="mailto:PLUG-discuss@lists.phxlinux.org" target="_blank">PLUG-discuss@lists.phxlinux.<wbr>org</a><br>To subscribe, unsubscribe, or to change your mail settings:<br><a href="http://lists.phxlinux.org/mailman/listinfo/plug-discuss" target="_blank">http://lists.phxlinux.org/<wbr>mailman/listinfo/plug-discuss</a></div><br></div></div><br>------------------------------<wbr>---------------------<br>
PLUG-discuss mailing list - <a href="mailto:PLUG-discuss@lists.phxlinux.org">PLUG-discuss@lists.phxlinux.<wbr>org</a><br>
To subscribe, unsubscribe, or to change your mail settings:<br>
<a href="http://lists.phxlinux.org/mailman/listinfo/plug-discuss" rel="noreferrer" target="_blank">http://lists.phxlinux.org/<wbr>mailman/listinfo/plug-discuss</a><br></blockquote></div></div>