{"id":35688,"date":"2022-04-26T16:04:21","date_gmt":"2022-04-26T20:04:21","guid":{"rendered":"https:\/\/mjtsai.com\/blog\/?p=35688"},"modified":"2022-04-27T14:37:41","modified_gmt":"2022-04-27T18:37:41","slug":"infinite-mac","status":"publish","type":"post","link":"https:\/\/mjtsai.com\/blog\/2022\/04\/26\/infinite-mac\/","title":{"rendered":"Infinite Mac"},"content":{"rendered":"

Mihai Parparita<\/a> (tweet<\/a>, Hacker<\/a> News<\/a>):<\/p>\n

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I’ve extended James Friend’s in-browser Basilisk II port to create a full-featured classic 68K Mac in your browser. You can see it in action at system7.app<\/a> or macos8.app<\/a>.<\/p>\n

[…]<\/p>\n

At this point I switched my approach to downloading pieces of the disk image on demand, instead of all upfront. After some false<\/a> starts<\/a>, I settled on an approach<\/a> where the disk image is broken up into fixed-size content-addressed 256K chunks. Filesystem requests from Emscripten are intercepted, and when they involve a chunk that has not been loaded yet, they are sent off to a service worker who will load the chunk over the network. Manually chunking (as opposed to HTTP range requests<\/a>) allows each chunk to be Brotli-compressed (ranges technically support compression too, but it’s lacking<\/a> in the real world). Using content addressing makes the large number of identical chunks from the empty portion of the disk map to the same URL. There is also basic prefetching support<\/a>, so that sequential reads are less likely to be blocked on the network.<\/p>\n

Along with some old fashioned web optimizations<\/a>, this makes the emulator show the Mac’s boot screen in a second, and be fully booted in 3 seconds, even with a cold HTTP cache.<\/p>\n

[…]<\/p>\n

While Emscripten has an IDBFS mode<\/a> where changes to the filesystem are persisted via IndexedDB, it’s not a good fit for the emulator, since it relies on there being an event loop, which is not the case in the emulator worker. Instead I used an approach similar to uploading<\/a> to send the contents of a third ExtFS “Saved” directory, which can then be persisted using IndexedDB on the browser side.<\/p>\n<\/blockquote>\n

It includes BBEdit 2, CodeWarrior 4, GraphicConverter, Hotline, KPT Bryce, Netscape, and lots of games.<\/p>\n\n

Previously:<\/p>\n