{"id":112660,"date":"2026-08-31T07:00:00","date_gmt":"2026-08-31T14:00:00","guid":{"rendered":"https:\/\/devblogs.microsoft.com\/oldnewthing\/?p=112660"},"modified":"2026-08-31T18:24:48","modified_gmt":"2026-09-01T01:24:48","slug":"20260831-00","status":"publish","type":"post","link":"https:\/\/devblogs.microsoft.com\/oldnewthing\/20260831-00\/?p=112660","title":{"rendered":"AWE does not require PAE, though PAE makes it much more useful"},"content":{"rendered":"<p>The Address Windowing Extensions (AWE) is a feature of Windows that allows programs to allocate physical memory and map them on a page-by-page basis into a region of address space (the &#8220;address window&#8221;). PAE is the Physical Address Extension, which is a feature of the x86-32 CPU that allows a 32-bit processor to generate physical addresses larger than 32 bits, thereby allowing it to access more than 4GB of physical motherboard RAM.<\/p>\n<p>Some time ago, I noted that <a title=\"Myth: In order to use AWE, you must enable PAE\" href=\"https:\/\/devblogs.microsoft.com\/oldnewthing\/20040819-00\/?p=38123\"> AWE does not require PAE<\/a>. The two features operate independently, but they are useful together.<\/p>\n<p>If you use AWE without PAE, then your 32-bit Windows system can access only 4GB of onboard memory, so the feature of AWE that gives you access to lots of physical memory is of limited use: The system has only 4GB of memory to begin with, so that&#8217;s all that you can get. You wrote a lot of complex code for a high-RAM scenario when there isn&#8217;t really a lot of RAM available to take advantage of it.<\/p>\n<p>It&#8217;s like getting a large teapot for making a single cup of tea: Your teapot has the capacity to hold a large amount of tea, but you&#8217;re going to put just one cup&#8217;s worth in it.<\/p>\n<p>This is all largely historical information, since 64-bit processes running on 64-bit systems can allocate more than 4GB of memory and use it in the normal way. No special hoops necessary.<\/p>\n<p><b>Note<\/b>: One thing that AWE does give you is the ability to allocate physical non-pageable memory. Again, you can use this feature whether or not you have also enabled PAE.<\/p>\n<p><b>Note 1<\/b>: A 32-bit program that uses AWE will still run on a 64-bit system provided the 64-bit system uses the same page size as the 32-bit system. Looking at the <a title=\"What are the page sizes used by Windows on various processors?\" href=\"https:\/\/devblogs.microsoft.com\/oldnewthing\/20210510-00\/?p=105200\"> table of page sizes used by Windows<\/a>, it means that an x86-32 program (4KB page size) can run on an x86-64 system and an AArch64 system, but not an Itanium.<\/p>\n","protected":false},"excerpt":{"rendered":"<p>All dressed up with nowhere to go.<\/p>\n","protected":false},"author":1069,"featured_media":111744,"comment_status":"open","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"_acf_changed":false,"footnotes":""},"categories":[1],"tags":[25],"class_list":["post-112660","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-oldnewthing","tag-code"],"acf":[],"blog_post_summary":"<p>All dressed up with nowhere to go.<\/p>\n","_links":{"self":[{"href":"https:\/\/devblogs.microsoft.com\/oldnewthing\/wp-json\/wp\/v2\/posts\/112660","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/devblogs.microsoft.com\/oldnewthing\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/devblogs.microsoft.com\/oldnewthing\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/devblogs.microsoft.com\/oldnewthing\/wp-json\/wp\/v2\/users\/1069"}],"replies":[{"embeddable":true,"href":"https:\/\/devblogs.microsoft.com\/oldnewthing\/wp-json\/wp\/v2\/comments?post=112660"}],"version-history":[{"count":1,"href":"https:\/\/devblogs.microsoft.com\/oldnewthing\/wp-json\/wp\/v2\/posts\/112660\/revisions"}],"predecessor-version":[{"id":112661,"href":"https:\/\/devblogs.microsoft.com\/oldnewthing\/wp-json\/wp\/v2\/posts\/112660\/revisions\/112661"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/devblogs.microsoft.com\/oldnewthing\/wp-json\/wp\/v2\/media\/111744"}],"wp:attachment":[{"href":"https:\/\/devblogs.microsoft.com\/oldnewthing\/wp-json\/wp\/v2\/media?parent=112660"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/devblogs.microsoft.com\/oldnewthing\/wp-json\/wp\/v2\/categories?post=112660"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/devblogs.microsoft.com\/oldnewthing\/wp-json\/wp\/v2\/tags?post=112660"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}