rfellman@ucsd.edu (Ronald D. Fellman) (11/14/89)
I have a Motorola XC68851 RC16 PMMU and a MacII loaded with 5 Megs of RAM. Is there any GOOD reason to plug in the PMMU given that I almost never run out of RAM? I am therefore not interested in the RAM disk program. As I understand it, the 6.0.3 version of the operating sys couldn't care less about PMMUs. Why, therefore is there SO much fuss about PMMUs? -ron fellman
rcfische@polyslo.CalPoly.EDU (Raymond C. Fischer) (11/15/89)
In article <7450@sdcsvax.UCSD.Edu> rfellman@ucsd.edu (Ronald D. Fellman) writes: >I have a Motorola XC68851 RC16 PMMU and a MacII loaded with 5 Megs of >RAM. Is there any GOOD reason to plug in the PMMU given that I almost >never run out of RAM? I am therefore not interested in the RAM disk >program. As I understand it, the 6.0.3 version of the operating sys >couldn't care less about PMMUs. Why, therefore is there SO much fuss >about PMMUs? Because virtual memory is the latest fad in the Mac world and everyone is jumping on the bandwagon. Consider ... System 7 is not here yet. Real memory is $80/meg. Disk storage is $10 to $15 per meg. A PMMU is $200. Virtual memory is slower than real memory. If _you_ want 8Mb, then the cost is ... Real: $80x4=$320 (1Mb SIMMs) $-20x4=$-80 (old 256k SIMMs) ----------- $240 (Total for 8Mb real) Virtual: $200 (PMMU) $12x8=$96 (disk space) --------- $296 (Total for 8Mb virtual) I have 5Mb of memory in my SE/30 and although the 68030 in it can handle demand paged virtual memory, I'm not likely to use it because 1) 5Mb is enough, and 2) I don't have 8 or 16 Mb of free disk space to use for paging. Ray Fischer rcfische@polyslo.calpoly.edu
d88-jwa@nada.kth.se (Jon Watte) (11/15/89)
In article rfellman@ucsd.edu (Ronald D. Fellman) writes: >couldn't care less about PMMUs. Why, therefore is there SO much fuss >about PMMUs? Because System 7 will be here any moment now... with virtual memory for those with PMMU. I DO run out of memory (5 megs) sometimes, but then, I have increased memory for the finder, ResEdit, Think C 4.0 and various other programs, together with a 1300 kB system memory partition (Nope, no cache, no fonts) Also, someone said that Motorola would discontinue the 68851 PMMU, but that was false alarm (it was the 68841) People got upset, though. The sun always shines in my mac h+ -- This .signature is longer than 4 lines. If you'd like to see it in whole, please send a note to me. I'm h+@nada.kth.se and also h+@proxxi.se 8')