{"id":882,"date":"2014-07-29T22:13:54","date_gmt":"2014-07-29T22:13:54","guid":{"rendered":"http:\/\/retroramblings.net\/?p=882"},"modified":"2026-08-14T12:56:44","modified_gmt":"2026-08-14T12:56:44","slug":"how-many-angels","status":"publish","type":"post","link":"https:\/\/retroramblings.net\/?p=882","title":{"rendered":"How many angels&#8230;"},"content":{"rendered":"<p><strong>&#8230; can dance on the head of a pin?<\/strong><\/p>\n<p>I have no idea &#8211; but I do know how many ZPUFlex processors will fit in a DE1 dev board: 25!\u00a0 [Edit: I&#8217;ve since managed to squeeze in another one &#8211; so 26!]<\/p>\n<p><iframe loading=\"lazy\" src=\"\/\/www.youtube.com\/embed\/w13FUhnuNN4\" height=\"315\" width=\"420\" allowfullscreen=\"\" frameborder=\"0\"><\/iframe><\/p>\n<p>OK, I&#8217;m stretching things a little to claim that 25 fully-featured ZPUFlex CPUs will fit on the DE1, because these have a really tiny ROM and very minimal supporting logic, so Quartus can optimise the hell out of the design &#8211; but it still seemed like a fun demo.<\/p>\n<p>Source, as always, can be found <a href=\"https:\/\/github.com\/robinsonb5\/ZPUDemos\">on GitHub<\/a>.<\/p>\n<p>[EDIT: The M4K memory blocks on the DE1&#8217;s Cyclone II support 32-bit data width, but not in full dual-port mode, where the data width is limited to 16-bit.\u00a0 This means that no matter how small the ZPU&#8217;s ROM\/StackRAM, it will occupy a minimum of 2 M4Ks.\u00a0 If it weren&#8217;t for this fact, I think the DE1 could take 3 further ZPUs.\u00a0 As it is, it&#8217;s possible to add just one more instance of the ZPU, and the code on github now reflects this.\u00a0 The record for the maxmium number of soft CPUs in a single project on the DE1 board is now 26.\u00a0 Unless you know diffferent!]<\/p>\n","protected":false},"excerpt":{"rendered":"<p>&#8230; can dance on the head of a pin? I have no idea &#8211; but I do know how many ZPUFlex processors will fit in a DE1 dev board: 25!\u00a0 [Edit: I&#8217;ve since managed to squeeze in another one &#8211; &hellip; <a href=\"https:\/\/retroramblings.net\/?p=882\">Continue reading <span class=\"meta-nav\">&rarr;<\/span><\/a><\/p>\n","protected":false},"author":2,"featured_media":0,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[4,9,8],"tags":[],"class_list":["post-882","post","type-post","status-publish","format-standard","hentry","category-fpga","category-geekery","category-hardware"],"_links":{"self":[{"href":"https:\/\/retroramblings.net\/index.php?rest_route=\/wp\/v2\/posts\/882","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/retroramblings.net\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/retroramblings.net\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/retroramblings.net\/index.php?rest_route=\/wp\/v2\/users\/2"}],"replies":[{"embeddable":true,"href":"https:\/\/retroramblings.net\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=882"}],"version-history":[{"count":9,"href":"https:\/\/retroramblings.net\/index.php?rest_route=\/wp\/v2\/posts\/882\/revisions"}],"predecessor-version":[{"id":2105,"href":"https:\/\/retroramblings.net\/index.php?rest_route=\/wp\/v2\/posts\/882\/revisions\/2105"}],"wp:attachment":[{"href":"https:\/\/retroramblings.net\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=882"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/retroramblings.net\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=882"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/retroramblings.net\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=882"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}