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Showing posts from October, 2023

What is intel FDIV bug?

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The Pentium FDIV bug is a hardware bug affecting the floating-point unit (FPU) of the early Intel Pentium processors. Because of the bug, the processor would return incorrect binary floating point results when dividing certain pairs of high-precision numbers. The bug was discovered in 1994 by Thomas R. Nicely, a professor of mathematics at Lynchburg College The term "FDIV" refers to "Floating-point Divide," which is an operation used in computer processors to divide floating-point numbers. Floating-point numbers are used to represent real numbers with a fractional part, and floating-point divide is the operation that calculates the result of dividing one floating-point number by another. This operation is crucial in various scientific, engineering, and mathematical calculations that involve real numbers with fractional components. The FDIV bug, as mentioned earlier, was a specific flaw in the way some Intel Pentium processors performed this floating-point divide ope...

What is the need for verification in VLSI design ?

  We need to verify the design to make sure that the design is an accurate representation of the specification without any bugs. Verification is carried out to ensure the correctness of design, to avoid surprises at a later time, to avoid a re-spin of the chip and to enter the market on time with good quality.

How to make an inverter without a transistor?

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 Inverter converts DC to AC, which is opposite to the working of rectifier. We can make an inverter from a battery and operate any AC devices like fan, light etc...Here the DC from the battery is converted to AC and then AC is stepped up using a transformer. But normally we depend on transistors for converting DC to AC, but without using transistor we can make it possible.  In the above circuit DC motor can be used to perform switching action , this is because of change in current during the rotation of armature which are of small gap between other armature coils. This switching action may not be visible when we use all type of DC motors. For the transformer primary due to the switching action AC will occur and secondary will step up the voltage. From the output we can connect any device and it will start working.

Verilog interview question. Draw the waveform for the code snippet

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  initial begin     #5 clk = 0;          forever clk = ~clk ;          end initial begin     rst=1;     repeat(3)          @ (negedge clk);               rst=0;               end *********************************solution******************************

Difference between Verilog and C ?

Verilog helps to design and describe digital systems while C helps to build operating systems, databases, compilers, interpreters, network drivers, etc.  The main difference between Verilog and C is that the Verilog is a Hardware Description Language while the C is a high level, general-purpose programming language.  

what is mean by local skew and global skew?

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Local skew is the difference in the arrival of clock signal at the clock pin of related flipflops.  Global skew is the difference in the arrival of clock signal at the clock pin of non related flops.

Is the real shape of clock signal in digital circuits is square?

 No, clock signal is not in square shape. In practical scenario it is trapezoid in shape.

What are asynchronous inputs to a flipflop?

  The normal inputs to the flipflops are synchronous, but we need to wait till the positive edge or negative edge of the clock to set or reset the flipflop. To overcome this disadvantage asynchronous inputs are used. These are preset and clear, at any time without waiting for the active edge of the clock flipflop can set or reset flipflop without waiting for the clock edge.