Microprocessors

802.11nMain article: IEEE_802.11n-2009

802.11n is a recent amendment which improves upon the previous 802.11 standards by adding Multiple-input_multiple-outputantennas (MIMO). 802.11n operates on both the 2.4GHz and the lesser used 5GHz bands. The IEEE has approved the amendment and it was published in October 2009.Answers.comAnswers.comPrior to the final ratification, enterprises were already migrating to 802.11n networks based on the Wi-Fi_Alliancecertification of products conforming to a 2007 draft of the 802.11n proposal.

The fundamental difference between a 32-bit and 64-bit microprocessor is what their names suggest: the size of the basic integer operations, also called the 'native' size of a CPU's calculations. The native size of a CPU determines a whole bunch of related characteristics.

For instance, all integer calculations are done using the native size; this matters in terms of performance for several reasons:

• if you add two integers smaller than the native size, it requires only a single operation.
• if you add two integers larger than the native size, you must perform 3 operations (add the upper values, add the lower values, then combine).

For instance, if you wanted to add two 20-bit numbers, on both the 32-bit CPU and 64-bit CPU it would require a single operation. However, if you wanted to add two 40-bit numbers, it would require only 1 operation on a 64-bit CPU, but 3 operations on a 32-bit CPU.

The native size of a CPU also determines things like the maximum addressable memory - thus, a 32-bit CPU can address up to 2^32 = 4GB of memory, while a 64-bit system can address up to 16 Exabytes. It also determines the minimum size of information that has to be processed - when fetching information from caches and memory, no operation can be done with information less than the native size. Thus, 64-bit CPUs are more demanding on memory subsystems, as they need to process information in 64-bit chunks, rather than 32-bit ones.

That will depend on both the architecture and implementation of the CPU.

The maximum number of bits that a CPU may process at once usually depends on its "register" size, but there are many other variables that influence and change this limit for a specific CPU. For example, a 64 bit processor may operate on 64 bits at once. Some processors may also have subprocessors that can handle even more bits at once, but those are usually not included in the processor's "bit size". As an example, Intel processors have MMX instructions that can handle up to 64 bits simultaneously, although the primary CPU is 32 bit. The largest known processor at the time of this answer operates on 128 bits at once, and there are rumors of even larger bit-processors on the horizon, although their power is largely unnecessary at this time. Some processors also have multiple parallel function units that can be running at the same time (e.g. integer units, floating point units, load/store unit) each of which processes a word of the appropriate number of bits for its data type simultaneously with all the other function units, this dramatically increases the possible number of bits processed at one time with no increase in "register" size. There have also been CPU architectures with large word sizes but some implementations of those architectures processed the bits in smaller groups to save cost (e.g. IBM System 360/30 like all System 360s had a 32 bit register size but processed it only 8 bits at once). Many early computers used serial ALU implementations, one that I know of had a 48 bit "register" size (stored in a continuously recirculating memory) but processed that only 1 bit at a time in the serial ALU (2 bits at a time when executing its square root instruction, but it still had to wait 2 bit times to get those 2 bits from the recirculating memory, so there was no speed increase).

A microprocessor incorporates the functions of a computer's central processing unit (CPU) on a single integrated circuit (IC, or microchip). It is a multipurpose, programmable, clock-driven, register based electronic device that accepts binary data as input, processes it according to instructions stored in its memory, and provides results as output.

To understand how a microprocessor works, it is helpful to look inside and learn about the logic used to create one. You can also learn about assembly language - the native language of a microprocessor - and many of the things that engineers can do to boost the speed of a processor.

A microprocessor executes a collection of machine instructions that tell the processor what to do. Based on the instructions, a microprocessor does three basic things:

• Using its ALU (Arithmetic/Logic Unit), a microprocessor can perform mathematical operations like addition, subtraction, multiplication and division. Modern microprocessors contain complete floating point processors that can perform extremely sophisticated operations on large floating point numbers.
• A microprocessor can move data from one memory location to another
• A microprocessor can make decisions and jump to a new set of instructions based on those decisions.

There may be very sophisticated things that a microprocessor does, but those are its three basic activities.

This is about as simple as a microprocessor gets. This microprocessor has:

• an address bus (that may be 8, 16 or 32 bits wide) that sends an address to memory
• a data bus (that may be 8, 16 or 32 bits wide) that can send data to memory or receive data from memory
• a RD (Read) and WR (Write) line to tell the memory whether it wants to set or get the addressed location
• a clock line that lets a clock pulse sequence the processor
• A reset line that resets the program counter to zero (or whatever) and restarts execution.

Let's assume that both the address and data buses are 8 bits wide in this example.

Here are the components of this simple microprocessor:

• Registers A, B and C are simply latches made out of flip-flops.
• The address latch is just like registers A, B and C.
• The program counter is a latch with the extra ability to increment by 1 when told to do so, and also to reset to zero when told to do so.
• The ALU could be as simple as an 8-bit adder (See the section on adders in How Boolean Logic Works for details), or it might be able to add, subtract, multiply and divide 8-bit values. Let's assume the latter here.
• The test register is a special latch that can hold values from comparisons performed in the ALU. An ALU can normally compare two numbers and determine if they are equal, if one is greater than the other, etc. The test register can also normally hold a carry bit from the last stage of the adder. It stores these values in flip-flops and then the instruction decoder can use the values to make decisions.
• There are 6 boxes marked "3-State" in the diagram. These are tri-state buffers. A tri-state buffer can pass a 1, a 0 or it can essentially disconnect its output (imagine a switch that totally disconnects the output line from the wire the output is heading toward). A tri-state buffer allows multiple outputs to connect to a wire, but only one of them to actually drive a 1 or a 0 onto the line.
• The instruction register and instruction decoder are responsible for controlling all of the other components.

There would also be control lines from the instruction decoder that would:

• Tell the A register to latch the value currently on the data bus.
• Tell the B register to latch the value currently on the data bus.
• Tell the C register to latch the value currently on the data bus.
• Tell the program counter register to latch the value currently on the data bus.
• Tell the address register to latch the value currently on the data bus.
• Tell the instruction register to latch the value currently on the data bus.
• Tell the program counter to increment
• Tell the program counter to reset to zero
• Activate any of the 6 tri-state buffers (6 separate lines)
• Tell the ALU what operation to perform
• Tell the test register to latch the ALUs test bits
• Activate the RD line
• Activate the WR line

Coming into the instruction decoder are the bits from the test register and the clock line, as well as the bits from the instruction register.

Yes. There are 1000 KB in 1 MB, so 16 MB is 16 000 KB.

Note! This is only approx calculations. It's actually 1024 KB in 1 MB, but that's not necessary for the calculations in this case.