Messages in this thread |  | | Date | Fri, 27 Dec 1996 19:33:52 +0200 (EET) | From | Tuomas Heino <> | Subject | Re: detecting > 64M on x86 |
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On Mon, 23 Dec 1996, Mark Hemment wrote:
> On Mon, 23 Dec 1996, Kimon Berlin wrote: > > "Larry M. Augustin" <lma@varesearch.com> wrote: > > > For example, the int 15h ah=c7 get memory map call returns a 42 byte > > > structure that includes how much memory is installed above and below > > > the 16M boundary. > > Ralf Brown's interrupt list says this is a PS/2 function > > "Standard" functions are int 15h, ax=e801h and int 15h, ax=e820h. e820h is > > closest to c7h, it returns a detailed memory map, but it has to be called > > several times, this would bloat setup.S . I think e801h would be enough > > for our purposes, > > > > Would there be a point in reporting the amount of cachable memory? I don't know > > if any other part of the kernel is designed to have a use for that (i.e. "fast > > pages" and "slow pages"). > > The memory sub-system isn't designed for fast/slow pages, but having the > information available would be v. useful. > From time-to-time, the question pops up; "I've installed extra > memory, and Linux runs slower!", and answer is (nearly) always due to > pages not being cached (not enough tag-ram, etc). If Linux could > display a warning for this condition, I'd vote for it. > The page allocation routines could also be modified to try and avoid > giving out slow pages, and start paging out when 'fast' pages become low > - a very simple solution, and probably wouldn't work v. well... > > > > No, I don't know the difference between local and system memory, and I > > "Local" would be on the motherboard, "system" on another board. Before memory > > modules (SIPPs and SIMMs), when you wanted more memory, you added an ISA (or MCA?) > > card with memory chips on it. Bandwidth was, um, suboptimal. > > Would there still be systems out there which have this archiecture? I > somehow doubt it, but watch out for the up coming NUMA machines. Each > 'node' will have local memory, but will be able (at a cost) to access > memory on other 'nodes' (a single address space). > I sold my last intel above boards (isa memory crap) three years ago... full sized isa boards with 2MB 130ns memory (laugh) ... sold 'em to some not-so-computer-oriented dummy... for $30 ;) Those stinky cards were _really_ slow... hope I'll never see 'em again ;)
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