Cache Coherence Essay

Over three decades of research on memory distortion leaves no doubt that memory can be altered with the use of suggestive techniques (Loftus & Pickrell, 1995). Such suggestive memory manipulation procedures strongly encourage people to recall past happenings and have repeatedly been used to create reccollections of events that never took place (Lynn, Lock, Loftus, Krackow & Lilienfeld, 2003). Elizabeth Loftus pioneered research into the effects of misleading suggestive information on memory, (Loftus, 1979; Loftus, Miller & Burns, 1978, Wells & Loftus 1984) and since, , researchers have successfully implanted memories of a wide variety of ficticious events through use of suggestive questions and statements; eg that individuals spilled punch at a wedding (Hyman, Husband & Billings, 1995), that they broke a window with their hand (Garry, Manning, Loftus & Sherman, 1996; Heaps & Nash, 1999), or that they got lost before age 3 (Mazzoni, Loftus, Seitz & Lynn, 1999), amongst many others.

Black Mirror: A Look Into Memory’s Darkest Chambers, How Technology and Science-Fiction are Merging like Never Before Andrea C. Hey University of San Francisco, 2017 2 Introduction Science-fiction writers have been intrigued by ideas of technology interlaced with human memory for hundreds of years. Explored extensively throughout the history of science fiction, the intermingling of memory and technology has played an imperative role in shaping modern technological advances. Memory technology has been studied and philosophized within the world of science-fiction.

In this report the author provides quantifiable results that show the available parallelism. The report defines various terminologies like Instruction Level parallelism, dependencies, Branch Prediction, Data Cache Latency, Jump prediction, Memory-address alias analysis etc. used clearly. A total of eighteen test programs with seven models have been examined and the results show significant effects of the variations on the standard models. The seven models reflect parallelism that is available by various compiler/architecture techniques like branch prediction, register renaming etc. The lack of branch prediction means that it finds intra-block

Compare and contrast reduced instruction set computer (RISC) with the complex Instruction set computer(CISC) [20]

Due to increased efficiency in Central Processing Units, most computers today are not used to their full potential. In fact, time interrupt handlers are issued as wait time, thus eating up CPU clock cycles. Virtualization gave the opportunity for multiple x86 Operating Systems to run on one machine. As CPU’s were

In 1978, Intel came out with the 8086 chip. This chip had 29,000 transistors, 20 address lines, and could “talk with up to 1MB of RAM ... designers never suspected anyone would ever need more than 1 MB of RAM” (PCMech, 2001, para. 4). Intel continued to produce its 8000 series chips, increasing the speed and the memory each time. In 1982, the 286 was the first processor to have protected mode, which was later used by Windows and other operating systems to allow programs to run separately but concurrently (PCMech, 2001, para. 8). In the late 1980s, Intel came out with the 386. The 386 was a huge step forward, as it had 275,000 transistors, came in a 33 MHz version, worked with 4 GB of RAM, and could support a virtual memory of 64 TB (PCMech, 2001, para. 9). In 2002, hyper-threading came out in the Pentium 4 HT, which meant that the CPU could be fooled into thinking it had two CPUs for each one that it actually had. Using hyper-threading along with additional cores has enhanced performance and speed because some cores are utilized for programs while others perform background jobs (Hoffman, 2014, paras. 6,7). Another way CPUs have been able to increase speed is by raising the number of cores per CPU socket, and utilizing an I/O Hub “called QuickPath Interconnect” (Santana, 2014, p. 565). The use of multiprocessing has been the key for the development of today’s CPUs.

architectures may prevent these systems to meet the performance required by many applications. For systems with intensive parallel communicat-ion requirements buses may not provide the required bandwidth, latency, and power consumption. A solution for such a communication bottleneck is the use of an

The shift to multicore Exascale systems will require applications to exploit million-way parallelism and overcome significant reductions in the bandwidth and volume of memory available to each CPU. There is another looming shift in the complexity of the node architectures that will be as big a challenge to software development as the exponential growth in processors. This is the potential shift to heterogeneous node architectures. The major challenges caused by the increasing scale and complexity HPC systems are cross cutting of the entire software stack. The software challenges include the rapid increase in parallelism, the memory wall, system heterogeneity and fault tolerance.

The CUDA platform is built around a large-scale similarity, where latency in memory access can be hidden waiting for other computations

Abstract— There have been various cases where the processors sharing memory where one process reads and other writes when a processor is sharing is reading requires the memory to be used by various process but it does not create a problem when the process sharing memory are reading the memory the problem arises when the there is write operation is conducted. The write operation makes a change in memory which when utilized by another processor may requires use of previous value which may be not present now giving an error which has developed for the need of development of cache coherence which has it protocols implemented to prevent duplication, utilization, and updating of memory values used by various process in a control processing unit. Cache Coherence has various protocols that have been discussed are directory based, snooping, snarfing and distributed shared memory there have been various protocols that have been implanted in and new methods are being researched by various leading companies such as AMD, Nvidia, Intel and have been researched for better performance and solving issues. The paper discusses the various protocols used for implementation of cache coherence in processes.

The project clearly introduces us to the concepts of distributed memories, remote procedure calls, shared memory, concurrency, etc. thereby leveraging our knowledge and

In this paper, we will cover the memory management of Windows NT which will be covered in first section, and microprocessors which will be covered in second section. When covering the memory management of Windows NT, we will go through physical memory management and virtual memory management of that operating system. In virtual memory management section, we will learn how Windows NT managing its virtual memory by using paging and mapped file I/O.

By implementing multi-core processors, we can dramatically increase a computer’s capabilities and computing resources, providing better responsiveness, improving multithreaded throughput, and delivering the advantages of parallel computing to properly thread mainstream applications (Ramanathan). When multi-core processing was just beginning there were already immediate benefits. One immediate benefit was that multi-core processors improved an operating system’s ability to multitask applications. For instance, say you have a virus scan running in the background while you’re working on your word-processing application (Ramanathan). Another major multi-core benefit comes from individual applications optimized for multi-core processors (Ramanathan). These applications, when properly programmed, can split a task into multiple smaller tasks and run them in separate threads

Multiprocessor systems have been used for many years, and high-end programmers are familiar with the techniques to exploit multiprocessors for higher performance levels.

The major dificulty encountered due to extensive use of parallelism is the existence of branch instructions in the set of instructions presented to the processor for execution: both conditional and unconditional branch instructions in the pipeline. If the instructions under execution in the pipeline does not bring any change in the control flow of the program, then there is no problem at all. However, when the branch instruction puts the program under execution to undergo a change in the flow of control, the situation becomes a topic of concern as the branch instruction breaks the sequential flow of control, leading to a situation what is called pipeline stall and levying heavy penalties on processing in the form of execution delays, breaks in the program flow and overall performance drop. Changes in the control flow affects the processor performance because many processor cycles must be wasted in ushing the pipeline already loaded with instructions from wrong locations and again reading-in the new set of instructions from right address. It is well known that in a highly parallel computer system, branch instructions can break the smooth flow of instruction fetching, decoding and execution. The consequence of this is in delay, because the instruction issuing must often wait until the actual branch outcome is known. To make things worse, the deeper the pipelining, more is the delay, and thus greater is the performance