{"resolved":true,"match_type":"uuid","source_type":"original_book","book_id":"38270854-596f-4a26-8183-db8c968c6020","title":"编码 隐匿在计算机软硬件背后的语言","author":null,"edition":null,"publisher":null,"year":null,"isbn":"9787121181184","requested_by":"printed_page","book":{"source_type":"original_book","book_id":"38270854-596f-4a26-8183-db8c968c6020","id":"38270854-596f-4a26-8183-db8c968c6020","uuid":"38270854-596f-4a26-8183-db8c968c6020","title":"编码 隐匿在计算机软硬件背后的语言","normalized_title":"编码隐匿在计算机软硬件背后的语言","author":null,"edition":null,"publisher":null,"year":null,"isbn":"9787121181184","isbns":["9787121181184","0123456789","6044921875","3039331000","0000000000","0000000000000"],"parsed":true,"ai_readable":true,"document_type":"book","page_count":438,"navigation_url":"https://workshop.closeclaw.top/ai/book/38270854-596f-4a26-8183-db8c968c6020","title_url":"https://workshop.closeclaw.top/ai/title/%E7%BC%96%E7%A0%81%20%E9%9A%90%E5%8C%BF%E5%9C%A8%E8%AE%A1%E7%AE%97%E6%9C%BA%E8%BD%AF%E7%A1%AC%E4%BB%B6%E8%83%8C%E5%90%8E%E7%9A%84%E8%AF%AD%E8%A8%80","fixed_page_url_template":"https://workshop.closeclaw.top/ai/book/38270854-596f-4a26-8183-db8c968c6020/page/{printed_page}","path_api_url_template":"https://workshop.closeclaw.top/api/ai/book/38270854-596f-4a26-8183-db8c968c6020/page/{printed_page}","read_url":"https://workshop.closeclaw.top/api/ai/read/38270854-596f-4a26-8183-db8c968c6020","page_url":"https://workshop.closeclaw.top/api/ai/books/38270854-596f-4a26-8183-db8c968c6020/page","search_url":"https://workshop.closeclaw.top/api/ai/books/38270854-596f-4a26-8183-db8c968c6020/search"},"page":{"printed_page":234,"pdf_page":250,"physical_index":250,"physical_index_base":0,"printed_page_status":"recognized","page_sha256":"f70a2127b0f5e3d38604d4c0c4ea1f6f7a12def17d15274485b9977f68f0b92d"},"chapter":"编码隐匿在计算机软硬件背后的语言","content":"从存储器中取出指令的过程称为取指令（instructionfetch)。在我们设计的加法器中每一条指令的长度是3个字节。因为每次从存储器取回个字节，所以取每条指令需要的时间为3个时钟周期。此外，一个完整的指令周期需要4个时钟周期。这些变化必然使得控制信号更加复杂。\n\n机器响应指令码做一系列操作的过程称为执行（execute）指令，但这并不能表明机器是一种有生命的东西，因为它不能自行分析机器代码并决定该做什么。每种机器码用其唯的方式触发多种控制信号，从而引发机器执行各种操作。\n\n注意，为了让上面的加法器更加有用，我们牺牲了运算速度。使用同样的振荡器，它的运算速度只有本章提到的第一个加法器的1/4。这验证了-个称为1ANSTAAFL的工程准则，它的意思是“天下没有免费的午餐”。通常上帝总是很公平的，你改进了机器的某个方面，则其他方面就会受到损失，有得就有失。\n\n如果不使用继电器构造这个电路的话，很显然，两个64KB的RAM阵列构成了电路中最主要的部分。事实上早就应该放弃这些部件了，甚至从一开始就应该决定只需要一个1KB的存储器。如果能确定所有的数据都可以存放在0000h\\~03FFh的地址空间中，那么使用一个小于64KB的存储器加法器也可以很好地工作。\n\n编码——隐匿在计算机软硬件背后的语言\n\n234","previous_page":233,"next_page":235}