REAL memory column in SDSF 4601

in the early 80s ... "big pages" were implemented for both VM and MVS. this didn't change the virtual page size ... but changed the unit of moving pages between memory and 3380s ... i.e. "big pages" were 10 4k pages (3380) that moved to disk and were fetched back in from disk. a page fault for any 4k page in a "big page" ... would result in the whole "big page" being fetched from disk.

note the original extended store ... wasn't so much an architecture issue, it was a packaging-technology issue. 3090s needed more electronic store than could be packaged within the proscribed latency of cache-memory fetch. the approach was to place the storage that couldn't be packaged for close access ... on a different bus under software control that burst transfers in (4k) page size units ... rather than the smaller cache line size units ... and then leverage the programming paradigm already in place for paging to-from disk.

this is somewhat LCS from 360 days (8mbytes of 8mic storage ... compared to 750ns storage on 360-67 or 2mic storage on 360-50). the simple strategy was to just consider it as adjunct of normal, faster storage and tolerate the longer fetch cycle. howeer, some installations tried to carefully allocate stuff in LCS ... that were lower use programs and-or purely cached data (like hasp buffers). however, some installactions actually implemented copying programs out of LCS to faster storage before end.

misc. past posts mentioning big pages.