{"id":3168,"date":"2026-01-02T21:35:04","date_gmt":"2026-01-02T21:35:04","guid":{"rendered":"https:\/\/elephantandchicken.co.uk\/stuffandnonsense\/?p=3168"},"modified":"2026-01-03T16:57:56","modified_gmt":"2026-01-03T16:57:56","slug":"basilisk-ii-emulator-floating-point-bug","status":"publish","type":"post","link":"https:\/\/elephantandchicken.co.uk\/stuffandnonsense\/?p=3168","title":{"rendered":"Basilisk II Emulator Floating Point Bug"},"content":{"rendered":"\n<h2 class=\"wp-block-heading\">Basilisk II Emulator Floating Point Bug<\/h2>\n\n\n\n<p>I&#8217;m not sure if it is just my specific installation, but I&#8217;ve noticed an issue in Basilisk II regarding floating point values, where the value displayed is incorrect. This has caused me issues a few times, but this evening, I worked out a partial solution.<\/p>\n\n\n\n<p>The issue seems to be in the FPU emulation itself. I use a IIci ROM in my copy. I found that if I set the CPU to either a full 68040 or a 68030 + FPU floating point values were wildly wrong. I then found that the vanilla &#8220;SANE&#8221; routines work, so if you set the emulator to 68030 (without an FPU) everything works just fine.<\/p>\n\n\n\n<p>This will slightly reduce software compatibility (although I doubt software that required the FPU would function correctly with the completely incorrect values I was getting), but will mean that software that doesn&#8217;t require a hardware FPU will run correctly.<\/p>\n\n\n\n<figure class=\"wp-block-image aligncenter size-full\"><img loading=\"lazy\" width=\"538\" height=\"448\" src=\"https:\/\/elephantandchicken.co.uk\/stuffandnonsense\/wp-content\/uploads\/2026\/01\/image.png\" alt=\"\" class=\"wp-image-3169\" srcset=\"https:\/\/elephantandchicken.co.uk\/stuffandnonsense\/wp-content\/uploads\/2026\/01\/image.png 538w, https:\/\/elephantandchicken.co.uk\/stuffandnonsense\/wp-content\/uploads\/2026\/01\/image-300x250.png 300w\" sizes=\"(max-width: 538px) 100vw, 538px\" \/><\/figure>\n\n\n\n<p>Update &#8211; dougg3 has noticed that the issue happens when he uses the IIci ROM, but not if he uses a later (LC 630) ROM.<\/p>\n\n\n\n<p>I have made a small testing tool, which is available for download here :<\/p>\n\n\n\n<p><a href=\"https:\/\/github.com\/Phipli\/FPUCheck\">https:\/\/github.com\/Phipli\/FPUCheck<\/a><a href=\"https:\/\/github.com\/Phipli\/FPUCheck\" target=\"_blank\" rel=\"noreferrer noopener\">https:\/\/github.com\/Phipli\/FPUCheck<\/a><\/p>\n\n\n\n<p><\/p>\n","protected":false},"excerpt":{"rendered":"<p>Basilisk II Emulator Floating Point Bug I&#8217;m not sure if it is just my specific installation, but I&#8217;ve noticed an issue in Basilisk II regarding floating point values, where the value displayed is incorrect. This has caused me issues a few times, but this evening, I worked out a partial solution. The issue seems to [&hellip;]<\/p>\n","protected":false},"author":1,"featured_media":3169,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"spay_email":"","jetpack_publicize_message":"","jetpack_is_tweetstorm":false},"categories":[13,283,12],"tags":[716,717,377,714,713,47,710,711,709,715,712],"jetpack_featured_media_url":"https:\/\/elephantandchicken.co.uk\/stuffandnonsense\/wp-content\/uploads\/2026\/01\/image.png","jetpack_publicize_connections":[],"jetpack_sharing_enabled":true,"jetpack_shortlink":"https:\/\/wp.me\/p7g9vY-P6","_links":{"self":[{"href":"https:\/\/elephantandchicken.co.uk\/stuffandnonsense\/index.php?rest_route=\/wp\/v2\/posts\/3168"}],"collection":[{"href":"https:\/\/elephantandchicken.co.uk\/stuffandnonsense\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/elephantandchicken.co.uk\/stuffandnonsense\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/elephantandchicken.co.uk\/stuffandnonsense\/index.php?rest_route=\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/elephantandchicken.co.uk\/stuffandnonsense\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=3168"}],"version-history":[{"count":2,"href":"https:\/\/elephantandchicken.co.uk\/stuffandnonsense\/index.php?rest_route=\/wp\/v2\/posts\/3168\/revisions"}],"predecessor-version":[{"id":3171,"href":"https:\/\/elephantandchicken.co.uk\/stuffandnonsense\/index.php?rest_route=\/wp\/v2\/posts\/3168\/revisions\/3171"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/elephantandchicken.co.uk\/stuffandnonsense\/index.php?rest_route=\/wp\/v2\/media\/3169"}],"wp:attachment":[{"href":"https:\/\/elephantandchicken.co.uk\/stuffandnonsense\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=3168"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/elephantandchicken.co.uk\/stuffandnonsense\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=3168"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/elephantandchicken.co.uk\/stuffandnonsense\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=3168"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}