Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP Path: utzoo!mnetor!uunet!seismo!rochester!pt!andrew.cmu.edu!bader+ From: bader+@andrew.cmu.edu (Miles Bader) Newsgroups: comp.arch Subject: Re: Phys vs Virtual Addr Caches Message-ID:Date: Thu, 16-Jul-87 10:57:11 EDT Article-I.D.: andrew.YUzCb7y00UkaU7k0Rj Posted: Thu Jul 16 10:57:11 1987 Date-Received: Sat, 18-Jul-87 07:05:27 EDT Organization: Carnegie Mellon University Lines: 12 In-Reply-To: <3904@spool.WISC.EDU> > Here's a question. Why do people build their caches to respond to physical > addresses instead of virtual addresses? Another way to state the question > is: why not put the VM -> PM translation logic next to (in parallel with) > the data cache, rather than before it? If different processes have different parts of their virtual address space mapped to the same physical memory, a physical cache allows them to share the same cache entries. Also, each cache entry in a virtual cache has to have a field describing which address map it's from if you don't want to have to flush the cache upon context switch, etc. -Miles