Virtual memory is conceptually simple but potentially devastating to performance. Every memory access must go through segmentation (add segment base, check limit) and then paging (look up the page table). Naively, paging alone requires two additional memory reads per access -- one for the page directory entry, one for the page table entry.
Sports events will create spikes in demand, for example at half time, while concerts produce "relentless, sustained pressure from start to finish".
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The first thing a multi-tasking operating system needs from hardware is isolation: multiple programs must share one processor without being able to read, write, or jump into each other's memory. The 80386 achieves this through memory protection -- two independent address translation layers.
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