On Tue, 13 Jun 2006, Johnny Billquist wrote: > Otto Moerbeek wrote: > > On Mon, 12 Jun 2006, Ted Mittelstaedt wrote: > > > > > > > > -----Original Message----- > > > > From: John Nemeth [mailto:[EMAIL PROTECTED] > > > > Sent: Monday, June 12, 2006 1:15 PM > > > > To: Ted Mittelstaedt; Nikolas Britton; Ted Unangst > > > > Cc: Hamorszky Balazs; firstname.lastname@example.org; email@example.com; > > > > [EMAIL PROTECTED] > > > > Subject: RE: wikipedia article > > > > > > > > > > > > On Nov 1, 6:11pm, "Ted Mittelstaedt" wrote: > > > > } > > > > } Prior to the release of the 80386 the Intel processors didn't have > > > > } memory protection which was a requirement of any processor running > > > > } the BSD kernel. > > > > > > > > This is not entirely true. The 80286 had memory protection. > > > > However, its memory protection was completely based on segments (i.e. > > > > it could not do paging). > > > > > > Oh, yeah, your right about that. Me bad. > > > > > > > > > > Also, it was only a 16 bit processor. > > > > > > What was the bit size of the CPU's originally used to write UNIX in Bell > > > Labs? > > The PDP-7 was/is an 18-bit machine. > > > What's more, iirc the MMU of the pdp11 isn't what we call a MMU today, > > it could not even do paging. > > You're wrong. You could easily do paging on a PDP-11, if you wanted to. The > main reasons this wasn't done are two. > 1) Each page is 8K. At the time, that was considered way too large pages for a > demand page system. > 2) The address space is only 64 per process, which means you only have 8 > pages. Not only is that perhaps a little little for meaningful paging (most > programs tend to refer to all 8 pages most of the time). The main memory on a > PDP-11 is furthermore 4 meg, so having a lot of processes full memory space in > physical memory at the same time is not a problem. > > The PDP-11 MMU is a beatiful MMU. Nothing like the crap Intel spits out. ;-)
I stand corrected. I always thought it coulnd't do paging, but I suppose it should be "due to various restrictions, it couldn't do meaningful paging". -Otto _______________________________________________ firstname.lastname@example.org mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-questions To unsubscribe, send any mail to "[EMAIL PROTECTED]"