https://community.intel.com/t5/Software-Tuning-Performance/How-to-find-out-whether-the-last-level-cache-is-shared-between/m-p/1030560#M4277 <P>Probably we should wait for the answer from Intel engineers.</P> Tue, 21 Oct 2014 14:42:08 GMT Bernard 2014-10-21T14:42:08Z https://community.intel.com/t5/Software-Tuning-Performance/How-to-find-out-whether-the-last-level-cache-is-shared-between/m-p/1030557#M4274 <P>My Macbook Air has an I7-4650U processor. How can I find out whether the 4MB last-level cache is shared by the CPU and the GPU or not?</P> Tue, 21 Oct 2014 06:09:28 GMT https://community.intel.com/t5/Software-Tuning-Performance/How-to-find-out-whether-the-last-level-cache-is-shared-between/m-p/1030557#M4274 Bo_W_2 2014-10-21T06:09:28Z https://community.intel.com/t5/Software-Tuning-Performance/How-to-find-out-whether-the-last-level-cache-is-shared-between/m-p/1030558#M4275 <P>I have found on Wikipedia cache article following sentence " <STRONG><EM>Intel <A title="Haswell (microarchitecture)" href="http://en.wikipedia.org/wiki/Haswell_(microarchitecture)"><U><FONT color="#0066cc">Haswell</FONT></U></A> CPUs with integrated <A title="Intel Iris Pro Graphics" class="mw-redirect" href="http://en.wikipedia.org/wiki/Intel_Iris_Pro_Graphics"><U><FONT color="#0066cc">Intel Iris Pro Graphics</FONT></U></A> have 128&nbsp;MB of eDRAM acting essentially as an L4 cache.<SUP class="reference" id="cite_ref-25"><A href="http://en.wikipedia.org/wiki/CPU_cache#cite_note-25"><U><FONT size="2"><FONT color="#0066cc"><SPAN>[</SPAN>24<SPAN>]</SPAN></FONT></FONT></U></A></SUP> The benefits of an L3 cache depend on the application's access patterns</EM></STRONG>."</P> <P>There is no mention about the L4 cache being shared.</P> Tue, 21 Oct 2014 11:00:13 GMT https://community.intel.com/t5/Software-Tuning-Performance/How-to-find-out-whether-the-last-level-cache-is-shared-between/m-p/1030558#M4275 Bernard 2014-10-21T11:00:13Z https://community.intel.com/t5/Software-Tuning-Performance/How-to-find-out-whether-the-last-level-cache-is-shared-between/m-p/1030559#M4276 <P>Thanks for your comment. Although I7-4650U is a Haswell CPU, it doesn't has L4 cache. I know many ivybridge CPUs share the last-level cache with GPUs. Not sure about the Haswell notebook CPUs.</P> Tue, 21 Oct 2014 13:49:08 GMT https://community.intel.com/t5/Software-Tuning-Performance/How-to-find-out-whether-the-last-level-cache-is-shared-between/m-p/1030559#M4276 Bo_W_2 2014-10-21T13:49:08Z https://community.intel.com/t5/Software-Tuning-Performance/How-to-find-out-whether-the-last-level-cache-is-shared-between/m-p/1030560#M4277 <P>Probably we should wait for the answer from Intel engineers.</P> Tue, 21 Oct 2014 14:42:08 GMT https://community.intel.com/t5/Software-Tuning-Performance/How-to-find-out-whether-the-last-level-cache-is-shared-between/m-p/1030560#M4277 Bernard 2014-10-21T14:42:08Z