On 11 Nov 1998, Gary L. Hennigan wrote: > "Henry Kingman" <[EMAIL PROTECTED]> writes: > | > On the other hand, if your chipset can't cache more than 64MB, going to > | > 80MB might actually make some things slower. I'm not sure if telling the > | > kernel "mem=64M" on an 80MB machine would be enough to fix that problem > | > or not.
Should be. in that case Linux won't ever address that memory, so it should have zero effect. Fortunately, we can do better - see below. > | Pasted below is an article from the ZDNet Web site about this. It seems to > | suggest that the L2 cache is somehow the limiting factor on RAM addressing > | capability (Is that right?). > > That's partially correct. All the Pentium processors will address > quite a bit more than 64MB of RAM, the question is whether or not your > motherboard can cache more than 64MB. It's a pretty complex issue, but > it's becoming less important now that the PII has it's cache packaged > in the CPU module. I believe the PII's cacheable limit is in the GB > range. Yeah, Intel crippled a few of its Pentium motherboard chipsets so they could only cache 64MB of RAM. If you touch RAM above 64MB, it's much slower. However... ...there are some tricks. Somewhere I saw an announcement for a set of patches to the kernel that allows it to treat memory above 64MB as a swap disk. Sure, it's slower than cached RAM, but *much* *much* *much* faster than an actual disk. ;-> Or, you can just use it as a plain ol' ramdisk. Put your source code and compiler on a ramdisk and you won't believe how fast you can compile code. :-> And on a laptop, RAM takes less power than a spinning disk. Anyway, as other have noted, to see how much RAM you need, try doing typical things with your system, and worst-case things, and use vmstat and free. I have 64MB in my desktop, and I've never used more than a meg or two of swap, even when compiling a kernel, running several xterms, emacs, and Netscape (which is an enourmous resource pig) and Apache. (I'll never go back to 16MB, beleive me.) Sincerely, Ray Ingles (248) 377-7735 [EMAIL PROTECTED] The above opinions are probably not those of FANUC Robotics. Yet.
