i would like some information on level 3 and 4 cache regarding pentium 4. if it is not yet implemented , are there any suggestions how it should be implemented. if it is implemented then what are its advantages and disadvantages. can anyone provide links so that i can study the topic in detail.
If it helps, you can think of main memory as your L4 cache. The levels really aren't that relevent, the only thing about having more levels in cache is so you have finer granularity when dealing with different programs. A very fast, very small L1, a somewhat fast, larger L2, a slower, but very large L3, and perhaps a really slow (compared to L1) but huge L4. Size and speed don't usually go together, bigger cache means slower cache and faster cache means smaller cache. Currently, most MPU designers for the desktop have found that having fast but small first and second level caches bring the most benefit for the cost. Recently, due to insane competition, Intel has been forced to add an L3 cache to its P4 line (at a substantial cost for not that much gain). There comes a point of diminishing return where adding more cache simply doesn't help performance enough to justify the price.
"We are Microsoft, resistance is futile." - Bill Gates, 2015.
With a overall lantency of 300 to 700 ns for 64 way server it start to have sense to add L4