CSC/ECE 506 Fall 2007/wiki1 7 2281: Difference between revisions
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= | = Introduction = | ||
Any changes in the organization of address spaces in the last 10 years? | This article features and answers the following queries: | ||
Are the interconnection structures different in new computers now than they were 10 years ago? | Any changes in the organization of address spaces in the last 10 years?<br> | ||
What is the size and capacity of current SMPs? How have supercomputers evolved since the Cray T3E? | Are the interconnection structures different in new computers now than they were 10 years ago?<br> | ||
What is the size and capacity of current SMPs?<br> | |||
How have supercomputers evolved since the Cray T3E? | |||
=== Shared Address Space === | |||
In the parallel computing world, this is the range of Memory addresses accessed / shared by multiple processors. | In the parallel computing world, this is the range of Memory addresses accessed / shared by multiple processors. | ||
"Shared Memory Multi-Processors" is a class of parallel machines which use Shared Address Space for parallelisation. | "Shared Memory Multi-Processors" is a class of parallel machines which use Shared Address Space for parallelisation. | ||
=== Trends in Organisation of address spaces === | === Trends in Organisation of address spaces === | ||
Typical usage of the address space is by a single processor to store data and instructions. As the need for faster processing of the data and instructions grew, Processors became more and more powerful, along with better organisation of the available memory space. Soon, we had multiple processors sitting on the same chip along with the either dedicated memories or with shared memories. To utilise memory better, different memory accessing schemes evolved ; Real Memory and Virtual Memory. Real memory access is a sequential access of the memory, where memory addresses are accessed one after the other. Such a scheme allowed utilisation of only the available address space. Virtual Memory has also evolved over the years. In the initial years, Memory access was done at two-levels. One of RAM and the other of either the hard-disk or the tape-drive using a technique called overlaying. Overlaying is a technique of replacing an unwanted block in RAM with a block which is required for the current execution. | |||
An improvement of the overlaying technique is what is today called Paging. An intermediate technique called Segmentation also existed, but Segmentation had major drawbacks, especially when the segments were too large to handle. | |||
t | |||
All current virtual memory principles is based on Paging. Paging is a technique of breaking down the data into 4K "Pages", and then loading them onto the RAM from the lower memory as and when required. A "Translation Lookaside Buffer" (TLB) takes care of all the virtual to physical memory mappings, and using this table, the required data is transferred into the Main memory for access. | |||
Virtual memory, by way of combining the main memory with the lower memories like the hard-drive and the flash-drives, gives the user the feel of having virtually "infinite" memory addresses, though the primary memory might be limited to a particular Memory size. | |||
Pentium can access about 4GB of physical Memory and about 64TB of virtual Memory | Pentium can access about 4GB of physical Memory and about 64TB of virtual Memory | ||
Physical access has now become virtual access, where the user will feel that the memory to be accessed is infinite, | Physical access has now become virtual access, where the user will feel that the memory to be accessed is infinite, | ||
Revision as of 15:05, 5 September 2007
Introduction
This article features and answers the following queries:
Any changes in the organization of address spaces in the last 10 years?
Are the interconnection structures different in new computers now than they were 10 years ago?
What is the size and capacity of current SMPs?
How have supercomputers evolved since the Cray T3E?
In the parallel computing world, this is the range of Memory addresses accessed / shared by multiple processors. "Shared Memory Multi-Processors" is a class of parallel machines which use Shared Address Space for parallelisation.
Trends in Organisation of address spaces
Typical usage of the address space is by a single processor to store data and instructions. As the need for faster processing of the data and instructions grew, Processors became more and more powerful, along with better organisation of the available memory space. Soon, we had multiple processors sitting on the same chip along with the either dedicated memories or with shared memories. To utilise memory better, different memory accessing schemes evolved ; Real Memory and Virtual Memory. Real memory access is a sequential access of the memory, where memory addresses are accessed one after the other. Such a scheme allowed utilisation of only the available address space. Virtual Memory has also evolved over the years. In the initial years, Memory access was done at two-levels. One of RAM and the other of either the hard-disk or the tape-drive using a technique called overlaying. Overlaying is a technique of replacing an unwanted block in RAM with a block which is required for the current execution.
An improvement of the overlaying technique is what is today called Paging. An intermediate technique called Segmentation also existed, but Segmentation had major drawbacks, especially when the segments were too large to handle. t All current virtual memory principles is based on Paging. Paging is a technique of breaking down the data into 4K "Pages", and then loading them onto the RAM from the lower memory as and when required. A "Translation Lookaside Buffer" (TLB) takes care of all the virtual to physical memory mappings, and using this table, the required data is transferred into the Main memory for access.
Virtual memory, by way of combining the main memory with the lower memories like the hard-drive and the flash-drives, gives the user the feel of having virtually "infinite" memory addresses, though the primary memory might be limited to a particular Memory size.
Pentium can access about 4GB of physical Memory and about 64TB of virtual Memory Physical access has now become virtual access, where the user will feel that the memory to be accessed is infinite,
Since Virtual Memory mechanism includes the lower elements in the memory hierarchy for expanding memory addresses. Paging and Segmentation have also evolved to give better access to the Address space. Segmentation being older than Paging; Degmentation had limits, which were overcome by paging (4kb chunks)
Interconnection structure
Interconnection structures have changed over the last many years. Bus-type interconnects have replaced the conventional cross-bar switch type interconnects, giving the best of performance and cost.
Current SMPs (Symmetric Multiprocessing)
A Computer system containing 2 or more processors in the same box, with shared memory, but containing just one OS running on them is termed as a Symmetric multiprocessor system. The downtime of such a system is dependent on the weakest link, ie. the single processors; if one processor is down, the whole system is said to be down.
Supercomputer evolution since Cray T3E
Majority of the supercomputers run on some flavour of Unix or Linux. It has been predominantly Linux since 2004 [ref Wikipedia] There are special purpose Supercomputers available to solve specific problems ;Astrophysics computation and codebreaking ; Molecular Dynamics ; Deepblue for the game of chess;
Measure of computational speed has gone up to TFLOPS (Tera Floating Point Operations Per Second) and has been moving towards PFLOPS (Peta Floating Point Operations Per Second)
Clustered supercomputing, where a cluster of MIMD Multiprocessors are connected togethere, with each cluster's processor being a SIMD.
Current supercomputers can go beyond 300 TFLOPS.While Cray was about 4 GFLOPS.
References
Computer User: http://www.computeruser.com/resources/dictionary/definition.html?lookup=7776
Foldoc : http://foldoc.org/index.cgi?symmetric+multiprocessing
Searchdatacenter : http://searchdatacenter.techtarget.com/sDefinition/0,,sid80_gci214218,00.html
Wikipedia / Supercomputers: http://en.wikipedia.org/wiki/Supercomputers
Intel: http://www.intel.com/cd/ids/developer/asmo-na/eng/95581.htm?page=2