Path: ...!eternal-september.org!feeder3.eternal-september.org!news.eternal-september.org!.POSTED!not-for-mail From: Thomas Koenig Newsgroups: comp.arch Subject: Re: What is an N-bit machine? Date: Fri, 29 Nov 2024 19:17:50 -0000 (UTC) Organization: A noiseless patient Spider Lines: 24 Message-ID: References: <2024Nov29.090339@mips.complang.tuwien.ac.at> Injection-Date: Fri, 29 Nov 2024 20:17:51 +0100 (CET) Injection-Info: dont-email.me; posting-host="5d4558349bb9c64e96842221a4fd591b"; logging-data="1287598"; mail-complaints-to="abuse@eternal-september.org"; posting-account="U2FsdGVkX18DBIoWyjPI8yOmsG1vaYIpOve76rr8ea8=" User-Agent: slrn/1.0.3 (Linux) Cancel-Lock: sha1:XJnzbM4Wxi1cIHxW68P2R8KQkI0= Bytes: 2062 Anton Ertl schrieb: > In the early 1980s the width of the data bus of the main > implementation of an architecture was considered to be defining the > bitness of the architecture. This is especially noticable in the > 68000, which was usually described as 16-bit CPU, despite having > 32-bit address and 32-bit data registers, because it has a 16-bit data > bus. I think that even Motorola called it a 16-bit CPU. With low-cost > variants such as the 8088, the 68008, and later the 386SX, that idea > was not kept up. It had been my impression that the width of the ALU was the definition for many computers - the widest integer that can natively be handled. (That does not really fit for the low-end /360, but that was a 32-bit architecture, and worked for the mid- and high-end machines). The 68000 was indeed advertised as a 16-bit processor, the 68008 also had a 16-bit ALU. The original Nova with its 4-bit ALU does not really fit, I think Edson de Castro quipped was that it was a 4-bit computer masquerading as a 16-bit computer. (They later introduced real 16-bit computers). Notable counterexamples? (OK, the PDP-8/S :-)