4 Replies Latest reply on Sep 23, 2009 11:11 AM by jmerrill@mmm.com

    EM64T tag in processor description


      http://processorfinder.intel.com/details.aspx?sSpec=SLB3R describes the P8400 processor.

      http://processorfinder.intel.com/details.aspx?sSpec=SLGFE describes the P8700 processor.


      The former page says that the P8400 has EM64T technology; the page for the P8700 does not say that.  I followed the link on the former page to find out about EM64T but it reached a page that does not mention that technology specifically; it describes all the 64-bit advantages seemingly lumped together.


      For purposes of running VMWare or MS Virtual PC under Windows Vista or Windows 7, and for doing software development (e.g. MS Visual Studio) is the presence or absence of EM64T relevant to me?  Is it possible that all processors that have "Intel Virtualization Technology" actually have EM64T, but the web pages don't always list it?


      Any info would be appreciated

        • 1. Re: EM64T tag in processor description

          Hi there,


          Q. What is Intel® Extended Memory 64 Technology (Intel® 64)?

          A. Intel® Extended Memory 64 Technology (Intel® 64) is a new technology that enhances server and workstation platforms with 64 bit addressability and related instructions.

          Q. Which 32- and 64-bit modes are available, and under which conditions? Can I still run my 32-bit applications on an Intel processor utilizing Intel Extended Memory 64 Technology?

          Legacy ModeCompatibility Mode64-Bit Mode
          32-bit operating system64-bit operating system64-bit operating system
          32-bit applications32-bit applications64-bit applications
          32-bit drivers64-bit drivers64-bit drivers
          4GB address space64-bit flat virtual address space
          GPRs are 32-bitGPRs are 64-bit



          EM64T can only be utilized by 64-bit operating systems. Thus, 32-bit operating systems like Windows XP cannot be run under regular IA32 mode.


          Regarding VT,

          check on the site:



          The CPU needs to support VT and it needs to be enabled in the BIOS. Hence the board as well needs to support VT.


          All the best,




          • 2. Re: EM64T tag in processor description

            Thank you for your reply, but it answers none of my questions.  Isn't it the case that every recent Intel processor can operate in either 32-bit or 64-bit mode, can address more memory when a 64-bit OS is used than is possible when running under a 32-bit OS, and requires BIOS support to run in 64-bit mode?  The two processors mentioned have the same Bus Speeed, Cache Size, Manufacturing Technology, Core Stepping, CPUID String, Thermal Design, and Power requirements.  They differ only in  clock speed (and thus bus/core ratio and L2 cache speed) and in whether the EM64T tag is listed on the respective processorfinder detail pages.  (The same "feature section" says that one is Dual Core while the other doesn't say that, but I know that they are both Dual Core.  I'm suspecting that the lack of EM64T tag is not signficant.)


            Is there any difference in the functionality of those processors when used to run VMWare or Virtual Server under 64-bit Vista or 64-bit Windows 7?  If they have the same CPUID String and Stepping, would any OS treat them differently and provide different functionality when one is used vs the other?  The only potentially important difference in the descriptions Intel makes available is that one carries the EM64T tag and the other doesn't.  What might I lose if I choose a processor that is not marked EM64T?  Given the other technological items that are the same about these processors, it almost seems as though the EM64T tag was accidentally left off one of the processor description pages (and may be just a P/R item that carries no real significance).  That's what I'm trying to find out.


            I know that if a processor does not support "hardware virtualization" that it will run noticeably more slowly under VMWare, and will not work at all with newer versions of Virtual Server (which explicitly requires hardware virtualization).  The two processors I mentioned both support "Intel virtualization technology", but only one has a processorfinder detail page that says it supports EM64T.  What functionality will be missing, if any, when a processor does not carry the EM64T tag?

            • 3. Re: EM64T tag in processor description

              As far as I can tell, Intel renamed "EM64T" as "Intel 64". One clue is that http://www.intel.com/info/em64t redirects to http://developer.intel.com/technology/intel64/index.htm (an Intel 64 Architecture page). Also, The Inquirer, CPU World and Wikipedia all mention that Intel renamed EM64T to Intel 64.


              I was trying to find out a similar thing today and found the following two links for the above processors (which look more recent than the pages you posted). In these pages both Intel Virtualization Technology (VT) and Intel 64 are ticked for the P8400 and P8700. So, I'm assuming that these are two different properties of an Intel processor (as some processors have VT and not Intel 64 ticked).


              I have a P8700 and was trying to find out if it was capable of running a 64-bit host OS. For the present time, I'll be trying the XP Pro SP3 (32-bit) host OS and Vista Business/Home Premium (64-bit) guest OS using VMware Workstation 6.5. VMware provide a simple tool for checking whether your hardware is theoretically capable of this emulation. However, I'm not sure whether this software checks for the VT property only, or the VT property and the Intel 64 property.






              I hope that's clarified at least one aspect of your post - the confusing Intel processor specifications. Regarding your other questions, I'm afraid I don't have the answers to those - but would be interested to know also.

              1 of 1 people found this helpful
              • 4. Re: EM64T tag in processor description

                Thank you for the investigation and those links.  It seems that you've confirmed my suspicion that there isn't really a difference between those processors.


                FYI, there is a very small executable called "SecurAble.exe" (to determine if a processor is Able to be Secure) available from grc.com that I believe answers the relevant questions about a processor.  For example, for the processor in this machine it says that it has "maximum bit length" of 64, that it has hardware DEP, but that it does not have hardware virtualization.


                Thanks for your help.