Question

As described in the text (Chapter 11), the PCI-Express bus consists of thirty-two "lanes.” As of January 2009, each lane is capable of a maximum data rate of 500 MB per second. Lanes are allocated to a device 1, 2, 4, 8, 16, or 32 lanes at a time. Assume that a PCI-Express bus is to be connected to a high- definition video card that is supporting a 1920x1080 true-color (3 bytes per pixel) progressive scan monitor with a refresh rate of 60 frames per second. How many lanes will this video card require to support the monitor at full capability?

Answer 1

ANSWER:

Before beginning the solution , lets keep the following conversion in mind.

1GB=1024KB

1MB=1024KB

1KB=1024KB

1Byte= 8 Bits

= Given,an HD video, card,with configuration =(1920 * 1080)

= The number of pixels/frames = 1920*1080=2,073,600pixels/frames

= Given,The number of bytes pixels=3

so,no of bits/pixel=3*8=24 bits/pixel.

= Refresh rate of the video = 60 frames/second.

= so,

The video data rate is =2,073,600 pixels/frames * 24 bits/pixels*

60 frames/second

= 2,985,984,000 bits/second.

= Dividing by 8,

= 373,248,000 Bytes/second.

= Dividing 1024

= 364,500 kBytes/second.

= Dividing by 1024 again

= 355.95 mbytes/second.

= Each lane in the PCI - Express bus is capable by transmitting 500MB

per second.

= But our video transmission rate is only 355.95 MB per second.

= So, We will need only one single lane for the video card to support the

monitor at full capability as 500MB /second is greater than required

355.95 MBps.

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