{"id":59397,"date":"2023-08-20T16:00:56","date_gmt":"2023-08-20T20:00:56","guid":{"rendered":"http:\/\/pappp.net\/?guid=1f2b6417fb85d00a682a3346e6d782d7"},"modified":"2023-08-20T16:00:56","modified_gmt":"2023-08-20T20:00:56","slug":"only-8-chips-make-a-cpu","status":"publish","type":"post","link":"https:\/\/pappp.net\/?p=59397","title":{"rendered":"Only 8 Chips Make A CPU"},"content":{"rendered":"

Source: Hack a Day<\/a><\/p>\n

Article note: Ooh, that's a clever use of the ol' EPROM-as-lookup-table trick, to construct a bit-serial processor more or less by bolting bit-serial RAMs and ROMs onto said lookup table.<\/div>
\"\"<\/div>

We’re no stranger to homemade CPUs on these pages, but we think that [Jiri Stepanovsky]’s 16-bit serial CPU might be a little special. Why? It has an astonishingly low chip count, with only 8 ICs in total<\/a>. How on earth does he do it?<\/p>\n

While a traditional TTL CPU has a relatively high chip count due to a parallel data bus, registers, and discrete ALU, this one takes a few shortcuts by opting for a one-bit serial bus with serial memory chips and an EPROM serving as a look-up-table ALU. Perhaps the most interesting result of this architecture is that it also allows the CPU to dispense with registers, like the Texas Instruments 16-bit chips back in the day. They all live in memory. You can see it below the break in action, streaming a video to a Nokia-style LCD.<\/p>\n

Such a CPU would indeed have been unlikely to have been made back in the day due to the prohibitive cost of buying and programming such a large EPROM. However, old computers like the EDSAC also used a serial data path and mercury delay line memory to manage complexity. But for a solid-state CPU in 2023, we think the design is innovative. We think it would be challenging to reduce the chip count further — and no, we’re not counting designs that use a microcontroller to replicate a block of circuitry; that’s cheating — but we’re sure that somewhere there’s a designer with ideas for slimming the design further.<\/p>\n

<\/span><\/p>\n

<\/p>\n

Thanks to [Ken Boak] for the tip.<\/p>","protected":false},"excerpt":{"rendered":"

We\u2019re no stranger to homemade CPUs on these pages, but we think that [Jiri Stepanovsky]\u2019…<\/p>\n

Continue reading →<\/span><\/a><\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[226],"tags":[],"class_list":["post-59397","post","type-post","status-publish","format-standard","hentry","category-news-2"],"_links":{"self":[{"href":"https:\/\/pappp.net\/index.php?rest_route=\/wp\/v2\/posts\/59397","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/pappp.net\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/pappp.net\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/pappp.net\/index.php?rest_route=\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/pappp.net\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=59397"}],"version-history":[{"count":0,"href":"https:\/\/pappp.net\/index.php?rest_route=\/wp\/v2\/posts\/59397\/revisions"}],"wp:attachment":[{"href":"https:\/\/pappp.net\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=59397"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/pappp.net\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=59397"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/pappp.net\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=59397"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}