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[Editor’s introduction: Ulrich Drepper recently approached us asking if we The various components of a system, such as the CPU, memory. What Every Programmer Should Know About Memory has 22 ratings and 5 reviews. Jaseem said: I can only tell that Every Programmer by. Ulrich Drepper. pdfs/What Every Programmer Should Know About Memory – Ulrich Drepper ( ).pdf. b8fa4bb on Jun 5, @tpn tpn Checkpoint commit. 1 contributor.

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Ulrich’s article isn’t x86 specific, but most all of memoey benchmarks are on x86 hardware. In section 5 we will discuss more machine archi- controller with the possibility of local memory for each tectures and some technologies the Linux kernel provides processor.

Ulrich Drepper – Wikipedia

The transistor M is used to guard the access to the state. Refresh and try again. Documents Ressources professionnelles Informatique. It is the FSB speed and the theoretical 6.

RAM hardware design speed and parallelism. There is really not much the programmer can do about the refresh and the points in time when the commands are issued.

This problem, therefore, must to be taken into account. The procedure cannot be repeated indefinitely, the capacitor kemory be recharged at some point. Thank you Ulrich and LWN!

I believe I have found a small typo in the formula just above figure 2. The use of a capacitor means that reading UlrichDrepper Version 1. But I have upvoted your post. Dan Kruchinin 2, 11 What every programmer should know about memory, Part 1 Posted Sep 28, Then the precharge command would have to be delayed by one additional cycle since the sum kemory t RCDCL, and t RP since it is larger than the data transfer time drspper only 7 cycles.

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A DIMM[1] can be single-rank or dual-rank.

Two processors, even two “half-speed” ones, can still do two tasks at the same time, and short computation bursts can well occur faster thanks ,emory increased likelihood of there being an idle core immediately available for the task. Msmory paper explains the structure of memory subsystems in use on modern commodity hardware, illustrating why CPU caches were developed, how they work, and what programs should do to achieve optimal performance by utilizing them.

What every programmer should know about memory, Part 1 []

Indeed, I don’t believe the comment even refers to Figures 2. There are in reality — obviously — many more complications.

For example, static RAM diagram could be explained better remember that this text is directed towards programmers, that may have not much EE related backgroundas well as DRAM refreshing it is left somewhat unclear how DRAM cell is returned to its initial value after practically destroying this value during read operation – this is say much more clear at block diagram from corresponding Wikipedia article than from Figure 2. DDR2 latencies go from 3 up to 7, I believe.


But if the number of cells grows this approach is not suitable anymore. Just a moment while we sign you in to your Goodreads account. In fact, a refresh is performed just by doing a read but throwing away the data.

“What every programmer should know about memory” – the PDF version

But it is not the only place where parallelism is used for bandwidth increase. Unfortunately, neither the structure nor the cost of using the memory subsystem of a computer or the caches on CPUs is well understood by most programmers. Doubling the frequency meansthe same.

You can coax gcc into emitting it, but if you want efficient loads of just one half of the object, you need ugly union hacks: Hyperthreading performance Posted Oct 4, If the application is making effective use of the cache, and is compiled to minimize pipeline bubbles, hyperthreading will just reduce your cache hit rate.

Note that these technical details tend to change rapidly, so the reader is advised to take the date of this writing into account. Alternatively, with higher frequencies, the same power envelope can be hit.