{"id":3415,"date":"2014-08-09T11:28:52","date_gmt":"2014-08-09T09:28:52","guid":{"rendered":"http:\/\/www.kameli.net\/marq\/?p=3415"},"modified":"2014-08-09T18:18:10","modified_gmt":"2014-08-09T16:18:10","slug":"amstrad-cpc6128-and-dual-crtc","status":"publish","type":"post","link":"http:\/\/www.kameli.net\/marq\/?p=3415","title":{"rendered":"Amstrad CPC6128 and dual CRTC"},"content":{"rendered":"<p>This time in English, as this blurb might benefit the international Google-using audience, too. As you might know, Amstrad CPC6128s came equipped with various versions of the CRTC chip: most of them clones of the Motorola 6845 (read more <a href=\"http:\/\/www.cpcwiki.eu\/index.php\/CRTC\">here<\/a>). The problem from a demoscener&#8217;s point of view is that they weren&#8217;t identical in every respect and, thus, very low-level demo stuff might not run. Both of my machines happened to have a CRTC0, which meant that I couldn&#8217;t run one of the top prods, <a href=\"http:\/\/www.pouet.net\/prod.php?which=53596\">From Scratch<\/a>. Some older demos might be the opposite, namely CRTC0-only.<\/p>\n<p>Various versions of the chip are occasionally available on eBay and I happened to come across a promising CRTC1. Changing the whole chip seems a bit brutal, but according to some accounts on CPC forums, you can piggyback two chips on top of each other and install a switch \u2013 unfortunately nobody seemed to give exact instructions. As my second 6128 was a bit busted anyway, I decided to give it a go. The best bet from a layman&#8217;s perspective seemed to be installing the switch to Vcc: bend pin 20 up on both chips, solder together the rest, and install a two-position switch that directs 5V to one CRTC or the other.<\/p>\n<p>And it works! <em>From Scratch<\/em> runs now and <a href=\"http:\/\/www.pouet.net\/prod.php?which=20226\">DTC<\/a> reports the version correctly depending on the switch position. See below how the kludge looks like:<\/p>\n<p><a href=\"http:\/\/www.kameli.net\/marq\/wp-content\/uploads\/2014\/08\/crtc-piggy.jpg\"><img loading=\"lazy\" decoding=\"async\" class=\"alignnone size-thumbnail wp-image-3416\" alt=\"crtc-piggy\" src=\"http:\/\/www.kameli.net\/marq\/wp-content\/uploads\/2014\/08\/crtc-piggy-150x150.jpg\" width=\"150\" height=\"150\" \/><\/a><\/p>\n<p>According to some rumors some people have installed even three chips on top of each other. After that you start getting close to the keyboard, tho. The contacts might be a bit hard to get working flawlessly, I guess. Then again, from a demo perspective a CRTC2 is a useless piece of junk \u2013 not much will work anyway. Funnily enough, the problem child is the <em>genuine<\/em> Motorola chip \ud83d\ude42 CRTC3 and 4 are part of the ASICs of the very last last CPC models, so they don&#8217;t exist in the wild as separate chips.<\/p>\n","protected":false},"excerpt":{"rendered":"<p>This time in English, as this blurb might benefit the international Google-using audience, too. As you might know, Amstrad CPC6128s came equipped with various versions of the CRTC chip: most of them clones of the Motorola 6845 (read more here). The problem from a demoscener&#8217;s point of view is that they weren&#8217;t identical in every [&hellip;]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[18,22,15],"tags":[],"class_list":["post-3415","post","type-post","status-publish","format-standard","hentry","category-demoskene","category-laitteet","category-retro"],"_links":{"self":[{"href":"http:\/\/www.kameli.net\/marq\/index.php?rest_route=\/wp\/v2\/posts\/3415","targetHints":{"allow":["GET"]}}],"collection":[{"href":"http:\/\/www.kameli.net\/marq\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"http:\/\/www.kameli.net\/marq\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"http:\/\/www.kameli.net\/marq\/index.php?rest_route=\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"http:\/\/www.kameli.net\/marq\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=3415"}],"version-history":[{"count":3,"href":"http:\/\/www.kameli.net\/marq\/index.php?rest_route=\/wp\/v2\/posts\/3415\/revisions"}],"predecessor-version":[{"id":3419,"href":"http:\/\/www.kameli.net\/marq\/index.php?rest_route=\/wp\/v2\/posts\/3415\/revisions\/3419"}],"wp:attachment":[{"href":"http:\/\/www.kameli.net\/marq\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=3415"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"http:\/\/www.kameli.net\/marq\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=3415"},{"taxonomy":"post_tag","embeddable":true,"href":"http:\/\/www.kameli.net\/marq\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=3415"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}