Static Ram and Dynamic Ram

What is the difference between stable drill in and dynamical obturate in my calculator? Your computer probably uses both static RAM and dynamic RAM at the kindred meter, save it uses them for unalike reasons because of the cost difference between the ii types. If you apprehend how dynamic RAM and static RAM chips deform inside, it is easy to see why the cost difference is in that respect, and you send away as well understand the names. Dynamic RAM is the most common type of computer storage in use today. Inside a dynamic RAM chip, each retrospection cell holds one bit of information and is made up of deuce separate a transistor and a capacitor.These are, of course, extremely low-spirited transistors and capacitors so that millions of them stick out fit on a mavin computer storage chip. The capacitor holds the bit of information a 0 or a 1 (see How Bits and Bytes Work for information on bits). The transistor acts as a switch that lets the control circuitry on the recollection chip tell the capacitor or change its state. A capacitor is like a sm every(prenominal) bucket that is able to store electrons. To store a 1 in the memory cell, the bucket is take hold full with electrons. To store a 0, it is emptied. The problem with the capacitors bucket is that it has a leak.In a matter of a few milliseconds a full bucket be put ins empty. Therefore, for dynamic memory to work, each the CPU or the memory ascendency has to come along and recharge all of the capacitors holding a 1 before they discharge. To do this, the memory controller reads the memory and consequently writes it right back. This refresh operation happens automatically thousands of quantify per second. This refresh operation is where dynamic RAM gets its name. Dynamic RAM has to be dynamically refreshed all of the time or it forgets what it is holding.The downside of all of this refreshing is that it takes time and slows down the memory. Static RAM uses a completely varied t echnology. In static RAM, a form of flip-flop holds each bit of memory (see How Boolean Gates Work for incident on flip-flops). A flip-flop for a memory cell takes 4 or 6 transistors along with some wiring, but never has to be refreshed. This draw and quarters static RAM signifi derrieretly faster than dynamic RAM. However, because it has to a greater extent parts, a static memory cell takes a lot more space on a chip than a dynamic memory cell.Therefore you get less memory per chip, and that makes static RAM a lot more overpriced. So static RAM is fast and expensive, and dynamic RAM is less expensive and slower. Therefore static RAM is use to create the CPUs move-sensitive lay aside, while dynamic RAM forms the larger frame RAM space Inside This Article 1. Introduction to How Caching Works 2. A Simple Example out front squirrel away 3. A Simple Example After Cache 4. Computer Caches 5. Caching Subsystems 6. Cache Technology 7. locality of Reference 8. Lots More Information pic If you stand been shopping for a computer, then you have comprehend the word hive up. Modern computers have both L1 and L2 caches, and many now also have L3 cache. You may also have gotten advice on the topic from well-meaning friends, perhaps some subject like Dont buy that Celeron chip, it doesnt have any cache in it It turns out that caching is an important computer-science process that appears on every computer in a concoction of forms. There are memory caches, hardware and software disk caches, page caches and more. Virtual memory is nevertheless a form of caching.In this article, we will explore caching so you brush aside understand why it is so important. A Simple Example Before Cache Caching is a technology based on the memory subsystem of your computer. The important purpose of a cache is to accelerate your computer while keeping the price of the computer low. Caching allows you to do your computer tasks more rapidly. To understand the basic idea behind a cach e system, lets start with a super- unreserved example that uses a librarian to demonstrate caching concepts. Lets imagine a librarian behind his desk. He is there to give you the take holds you ask for.For the sake of simplicity, lets say you cant get the hold ups yourself you have to ask the librarian for any entertain you want to read, and he fetches it for you from a set of stacks in a storeroom (the library of relative in Washington, D. C. , is set up this modality). First, lets start with a librarian without cache. The rootage customer arrives. He asks for the book Moby Dick. The librarian goes into the storeroom, gets the book, returns to the previse and gives the book to the customer. Later, the thickening comes back to return the book. The librarian takes the book and returns it to the storeroom.He then returns to his counter waiting for another customer. Lets say the next customer asks for Moby Dick (you saw it coming ). The librarian then has to return to the st oreroom to get the book he recently handled and give it to the client. Under this model, the librarian has to make a complete round trip to fetch every book even very touristed ones that are requested frequently. Is there a way to improve the performance of the librarian? Yes, theres a way we can put a cache on the librarian. In the next section, well look at this same example but this time, the librarian will use a caching system.A Simple Example After Cache Lets give the librarian a backpack into which he will be able to store 10 books (in computer terms, the librarian now has a 10-book cache). In this backpack, he will put the books the clients return to him, up to a maximum of 10. Lets use the prior example, but now with our new-and-improved caching librarian. The day starts. The backpack of the librarian is empty. Our first client arrives and asks for Moby Dick. No magic here the librarian has to go to the storeroom to get the book. He gives it to the client. Later, the cli ent returns and gives the book back to the librarian.Instead of returning to the storeroom to return the book, the librarian puts the book in his backpack and stands there (he checks first to see if the bag is full more on that later). Another client arrives and asks for Moby Dick. Before difference to the storeroom, the librarian checks to see if this claim is in his backpack. He finds it All he has to do is take the book from the backpack and give it to the client. Theres no journey into the storeroom, so the client is served more efficiently. What if the client asked for a title not in the cache (the backpack)?In this case, the librarian is less efficient with a cache than without one, because the librarian takes the time to look for the book in his backpack first. One of the challenges of cache design is to minimize the affect of cache searches, and modern hardware has reduced this time delay to practically zero. Even in our simple librarian example, the latency time (the wa iting time) of searching the cache is so small compared to the time to head back to the storeroom that it is irrelevant. The cache is small (10 books), and the time it takes to notice a turn a loss is only a tiny fraction of the time that a journey to the storeroom takes.From this example you can see some(prenominal) important facts approximately caching Cache technology is the use of a faster but smaller memory type to accelerate a slower but larger memory type. When using a cache, you mustiness check the cache to see if an item is in there. If it is there, its called a cache hit. If not, it is called a cache miss and the computer must wait for a round trip from the larger, slower memory area. A cache has some maximum size that is much Computer Caches A computer is a machine in which we measure time in very small increments.When the microprocessor accesses the main memory (RAM), it does it in about 60 nanoseconds (60 billionths of a second). Thats pretty fast, but it is muc h slower than the typical microprocessor. Microprocessors can have cycle times as short as 2 nanoseconds, so to a microprocessor 60 nanoseconds seems like an eternity. What if we build a special memory bank in the motherboard, small but very fast (around 30 nanoseconds)? Thats already two times faster than the main memory access. Thats called a level 2 cache or an L2 cache. What if we build an even smaller but faster memory system directly into the microprocessors chip?That way, this memory will be accessed at the speed of the microprocessor and not the speed of the memory peck. Thats an L1 cache, which on a 233-megahertz ( megacycle per second) Pentium is 3. 5 times faster than the L2 cache, which is two times faster than the access to main memory. Some microprocessors have two levels of cache built right into the chip. In this case, the motherboard cache the cache that exists between the microprocessor and main system memory becomes level 3, or L3 cache. There are a lot of subs ystems in a computer you can put cache between many f them to improve performance. Heres an example. We have the microprocessor (the fastest thing in the computer). Then theres the L1 cache that caches the L2 cache that caches the main memory which can be used (and is often used) as a cache for even slower peripherals like hard disks and CD-ROMs. The hard disks are also used to cache an even slower medium your Internet connection The computer you are using to read this page uses a microprocessor to do its work. The microprocessor is the heart of any normal computer, whether it is a desktop machine, a boniface or a laptop.The microprocessor you are using might be a Pentium, a K6, a PowerPC, a Sparc or any of the many other brands and types of microprocessors, but they all do approximately the same thing in approximately the same way. If you have ever wondered what the microprocessor in your computer is doing, or if you have ever wondered about the differences between types of micro processors, then read on. In this article, you will learn how fairly simple digital logic techniques allow a computer to do its job, whether its playing a game or part checking a documentA microprocessor also known as a CPU or important processing unit is a complete computation engine that is fabricated on a single chip. The first microprocessor was the Intel 4004, introduced in 1971. The 4004 was not very powerful all it could do was add and subtract, and it could only do that 4 bits at a time. But it was amazing that everything was on one chip. Prior to the 4004, engineers built computers either from collections of chips or from discrete components (transistors wired one at a time). The 4004 powered one of the first takeout electronic calculators. pic Intel 8080 The first microprocessor to make it into a home computer was the Intel 8080, a complete 8-bit computer on one chip, introduced in 1974. The first microprocessor to make a real splash in the market was the Intel 808 8, introduced in 1979 and incorporated into the IBM PC (which first appeared around 1982). If you are familiar with the PC market and its history, you know that the PC market moved from the 8088 to the 80286 to the 80386 to the 80486 to the Pentium to the Pentium II to the Pentium III to the Pentium 4.All of these microprocessors are made by Intel and all of them are improvements on the basic design of the 8088. The Pentium 4 can execute any piece of code that ran on the master copy 8088, but it does it about 5,000 times faster Microprocessor Progression Intel The following table helps you to understand the differences between the different processors that Intel has introduced over the years. Name Date Transistors Microns Clock speed Data Microprocessor Progression Intel The following table helps you to understand the differences between the different processors that Intel has introduced over the years.Name Date Transistors Microns Clock speed Data width MIPS 8080 1974 6,000 6 2 MHz 8 bits 0. 64 8088 1979 29,000 3 5 MHz 16 bits 8-bit bus 0. 33 80286 1982 134,000 1. 5 6 MHz 16 bits 1 80386 1985 275,000 1. 5 16 MHz 32 bits 5 80486 1989 1,200,000 1 25 MHz 32 bits 20 Pentium 1993 3,100,000 0. 8 60 MHz 32 bits 64-bit bus 100 Pentium II 1997 7,500,000 0. 35 233 MHz 32 bits 64-bit bus 300 Pentium III 1999 9,500,000 0. 25 450 MHz 32 bits 64-bit bus 510 Pentium 4 2000 42,000,000 0. 8 1. 5 GHz 32 bits 64-bit bus 1,700 Pentium 4 Prescott 2004 125,000,000 0. 09 3. 6 GHz 32 bits 64-bit bus 7,000 Compiled from The Intel Microprocessor Quick Reference Guide and TSCP Benchmark Scores Information about this table . rises. Clock speed is the maximum rate that the chip can be clocked at. Clock speed will make more sense in the next section. Data Width is the width of the ALU. An 8-bit ALU can add/subtract/multiply/etc. two 8-bit numbers, while a 32-bit ALU can manipulate 32-bit numbers.An 8-bit ALU would have to execute four educational activitys to add two 32 -bit numbers, while a 32-bit ALU can do it in one instruction. In many cases, the external data bus is the same width as the ALU, but not always. The 8088 had a 16-bit ALU and an 8-bit bus, while the modern Pentiums fetch data 64 bits at a time for their 32-bit ALUs. MIPS stands for millions of instructions per second and is a rough measure of the performance of a CPU. Modern CPUs can do so many different things that MIPS ratings lose a lot of their meaning, but you can get a general sense of the relative power of the CPUs from this column.From this table you can see that, in general, there is a relationship between clock speed and MIPS. The maximum clock speed is a function of the manufacturing process and delays within the chip. There is also a relationship between the number of transistors and MIPS. For example, the 8088 clocked at 5 MHz but only executed at 0. 33 MIPS (about one instruction per 15 clock cycles). Modern processors can often execute at a rate of two instructions per clock cycle. That improvement is directly related to the number of transistors on the chip and will make more sense in the next section.