A PC with a 486DX2 processor runs internally at 50Mhz. What speed would its external logic be running?
Answer: B
Correct answer: 25Mhz
The DX2 runs its core at twice the bus speed, so an internal 50 MHz means an external
\[ \frac{50}{2} = 25\ \text{MHz} \]
Clock doubling raised processor speed without requiring faster and more expensive motherboards.
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You are testing the resistance in Ohms of a fuse on a 15K amp system. If the fuse is good, the meter should read?
Answer: A
Correct answer: 0.0
A good fuse is a piece of wire, so its resistance is effectively zero and the meter reads 0.0. A blown fuse reads as an open circuit.
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The floppy drive uses which DMA (direct memory access) channel?
Answer: D
Correct answer: 2
The floppy controller uses DMA channel 2, which is why that channel is never available for anything else on a machine with a floppy drive.
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You have a system that periodically locks up. You have ruled out software, and now suspect that it is hardware. What should you do first that could help you narrow it down to the component at fault?
Answer: D
Correct answer: disable the CPU cache in CMOS
Switching the cache off in CMOS is done in seconds and needs no parts. If the lockups stop, the fault is in the cache; if they continue, the cache is cleared and the search moves on.
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A static jolt of as little of _____ volts can fry most any PC integrated circuit.
Answer: B
Correct answer: 30
Modern integrated circuits are damaged by discharges of a few tens of volts - far below the three thousand or so a person can feel. That gap is the whole reason for wrist straps: the damage is done long before anything is noticed.
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Which values are held in CMOS for the hard drive
Answer: A
Correct answer: size (heads, cylinders, sectors)
CMOS holds the drive's geometry so that the BIOS can address it before any operating system is loaded. Interrupt assignments and free space are not part of it.
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Before sending data, a modem sends a request to send signal, or RTS.
Answer: A
Correct answer: True
RTS, request to send, is raised by the sender to ask permission to transmit; the receiver answers with CTS. That exchange is the hardware handshake of RS-232.
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What is the best ground for a conductive work bench?
Answer: A
Correct answer: AC outlet
The bench is earthed to the ground pin of a properly wired AC outlet, which is the building's true earth. Grounding to another device or to a chassis only ties two floating points together.
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When a bearing in the power supply fan goes out, what should you replace?
Answer: D
Correct answer: power supply
The fan in a PC supply is inside a sealed unit carrying line voltage and large capacitors, so the whole power supply is replaced rather than opened. Its cost is far below the risk of working inside it.
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Every video card must have?
Answer: B
Correct answer: RAM
A video card must hold the image it is displaying, so it needs memory - the frame buffer, read out sixty or more times a second to refresh the screen. A processor of its own is optional; RAM is not.
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