"Justin C.Walker" wrote: > > On Monday, January 28, 2002, at 05:10 PM, Greg Shenaut wrote: > > >> I'd guess that the point deals with the use of "shared memory" between > >> processes for the purposes of sharing data. Given the granularity of > >> the PDP-11 "VM" hardware, it seemed like a bad tradeoff, and wasn't > >> considered useful until long after the PDP-11 went to the Boston > >> Computer Museum, where it sipped tea and complained about the Red Sox. > > > > Well, on PDP11s, which I used for V6, V7, and 2.8 & 2.9 BSD, you > > could share text memory, as has already been stated, and IIRC you > > could also share data memory after a vfork (once vfork became> > remember PDP/11 >architecture all that well either. > > You're correct; that's what I meant by the 'granularity' of the > hardware. You had to share a fairly hefty chunk of memory, so (except > for vfork-like-things), it put too much of a constraint on the use of > the sharing.
As far as I remember from reading the Lyons' book, there were 16 mapping descriptors for text and data each. I think, 1/16 of the address space is not too big, and in absolute values it's the size of today's pages (4KB). -SB To Unsubscribe: send mail to [EMAIL PROTECTED] with "unsubscribe freebsd-hackers" in the body of the message
