Information Technology Reference
In-Depth Information
Table 3.2
Example transfer rates
Device
Transfer rate
Application
Hard disk
4 MB/s
Typical transfer
Sound card
88 KB/s
16-bit, 44.1 kHz sampling
LAN
1 MB/s
10 Mbps Ethernet
RAM
66 MB/s
Microprocessor to RAM
Serial Communications
1 KB/s
9600 bps
Super VGA
15 MB/s
1024·768 pixels with 256 colours
For a graphics adaptor with a screen resolution of 1024·640, 64k colours (16-bit colour)
which is updated 20 times per second (20 Hz), the maximum transfer rate will be:
Transfer
rate
(max)
=
No.
of
pixels
per
screen
·
No.
of
bits
per
pixel
·
No.
of
screen
updates
(b/s)
=
(
1024
·
640
)
·
16
·
20
b/s
=
209
715
200
b/s
209
715
200
=
=
26
214
400
B/s
8
26
214
400
=
=
246.2
MB/s
1024
·
1024
The PCI Local bus has become a standard on most new PC systems and has replaced the VL-
local bus for graphics adaptors. It has the advantage over the VL-local bus in that it can
transfer at much higher rates. Unfortunately, most available software packages cannot use
the full power of the PCI bus because they do not use the full 64-bit data bus. PCI and VL-
local bus are discussed in the next chapter.
3.6
Exercises
3.6.1
How many bits are transferred in a single clock operation with the PC bus:
(a)
1
(b)
8
(c)
16
(d)
32
3.6.2
What is the standard clock frequency which is used in ISA transfers:
(a)
4.77 MHz
(b)
8 MHz
(c)
10 MHz
(d)
16 MHz
3.6.3
What is the maximum transfer rate for the ISA bus:
(a)
8 MB/s
(b)
16 MB/s
(c)
32 MB/s
(d)
64 MB/s
3.6.4
What is the maximum transfer rate for the EISA bus:
(a)
8 MB/s
(b)
16 MB/s
