mwm@eris.UUCP (11/22/86)
Just a few quick observations on segments: 1) Segments are not a new thing - Burroughs has been selling them on their large systems for over a decade now (two decades, maybe?). 2) The thing that everybody who works with unix should think of when the word "segments" comes up (after eighty-eighty sux, of course :-) is "Multics," followed by "slow." But Multics tried to support far more than is being discussed here. 3) Segments are a good thing, but only if you've got enough to be usefull (enough to store arrays as illith vectors), and each one is big enough to be ditto. "Enough" varies with time, of course. 4) You don't have to have a time overhead for having segments. After all, a VAX has segments already. 5) You don't have to have broken pointer semantics if you use segments. Scattering them around in a large, sparse address space works fine. 6) 32 bits isn't a big enough address space. You can (maybe) make something usefull out of it, but it probably won't be usefull in a few years. 7) The memory cost for segments should be small, and may be zero, depending on what kind of architechture you're trying to cram them into. 8) Segments are coming to Unix. See either MACH or the Karels&McKusick paper on the new BSD virtual memory system. <mike
billw@navajo.STANFORD.EDU (William E. Westfield) (11/26/86)
In article <1744@jade.BERKELEY.EDU>, mwm@eris.BERKELEY.EDU (Mike (Don't have strength to leave) Meyer) writes: > : > 6) 32 bits isn't a big enough address space. You can (maybe) make > something usefull out of it, but it probably won't be usefull in a few > years. > : Give me a break. Maybe (maybe!) 32 bits of address space wont be big enough for some applications in a few years, but that hardly means that you won't be able to do anything useful with a smaller address space. Quite a lot of people manage to get serious work done on machines with the good old 64K address space. I guess they don't know that they are using useless programs. BillW
bsteve@gorgo.UUCP (11/29/86)
In reply to: billw@navajo.UUCP in comp.arch who replied to: mwm@eris.BERKELEY.EDU >> : >> 6) 32 bits isn't a big enough address space. You can (maybe) make >> something usefull out of it, but it probably won't be usefull in a few >> years. >> : > >Give me a break. Maybe (maybe!) 32 bits of address space wont be big >enough for some applications in a few years, but that hardly means that >you won't be able to do anything useful with a smaller address space. > >Quite a lot of people manage to get serious work done on machines >with the good old 64K address space. I guess they don't know that >they are using useless programs. Really now Bill, why should we care to tie new software architecture to out-dated hardware architecture? The answer is that the old scumbag hardware won't support the next generation of application software. In fact, I'm not sure that a 64 bit address space will be sufficient in a few years. Some people still use hollerith cards...(gak!) -> "You can cut a tin can with it,... but you wouldn't want to." Steve Blasingame (Oklahoma City) ihnp4!occrsh!gorgo!bsteve