The best explanation of hyperthreading in reasonable terms has been this one. http://www.tomshardware.com/answers/id-1694436/hyperthreading-work.html On Sep 6, 2016 7:48 PM, "Tom Jones" wrote: > 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. > > 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. > > 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. > > 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. > > ------------------------------ > *From: *"David Schwartz" > *To: *"Main PLUG discussion list" > *Sent: *Tuesday, September 6, 2016 4:29:59 PM > *Subject: *Re: 4 cores and 8 threads > > AFAIK, the “cores” are 64-bit ALUs that can split into 32-bit pairs to run > 32-bit code. > > So an i7 has four x 64-bit cores that also work as 8×32-bit CPUs. > > 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. > > 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. > > (My base system is a Mac with a 2.8 GHz i7, 16 GB of RAM, and the latest > OS X.) > > -David Schwartz > > On Sep 6, 2016, at 3:53 PM, Keith Smith wrote: > > Hi, > > If an Intel CPU has 4 cores and 8 threads will it look like 8 cores to > VirtualBox when assigning resources to a guest? > > If so is there a way to determine which is a tread and which is actually a > core? > > Thanks!! Keith --------------------------------------------------- > PLUG-discuss mailing list – PLUG-discuss@lists.phxlinux.org To subscribe, > unsubscribe, or to change your mail settings: http://lists.phxlinux.org/ > mailman/listinfo/plug-discuss > > > > --------------------------------------------------- > PLUG-discuss mailing list - PLUG-discuss@lists.phxlinux.org > To subscribe, unsubscribe, or to change your mail settings: > http://lists.phxlinux.org/mailman/listinfo/plug-discuss > > > --------------------------------------------------- > PLUG-discuss mailing list - PLUG-discuss@lists.phxlinux.org > To subscribe, unsubscribe, or to change your mail settings: > http://lists.phxlinux.org/mailman/listinfo/plug-discuss >