Information Technology Reference
In-Depth Information
I didn't really have the heart to write back to the user and say that it was a made-up chip, so
I sent an email back saying that it was not available at the present time (which was true).
So why has the serial port become more popular than the parallel port. Well it's because
of one reason: since PC's started, the serial port has always been a standard port and most
manufacturers abide with it, whereas the parallel port was a quick fix so that the original PC
could communicate with a printer. In its standard form, it can only send information in a
single direction, and, even worse, only eight bits can be sent at a time. Nevertheless, it has
survived, and now has several uses, especially with printers, scanners and external CD-
ROMs. So it will hold the fort for a few years yet before the USB port takes over in creating a
truly integrated bus system. But, you may say, the USB port is serial. So why transmit one bit
at a time when you can transmit 8 or 16 or even 32 bits at a time. Well it's all to do with the
number of wires that must be connected. A serial bus always has the advantage over a paral-
lel bus, in that you only really need one signal line in a serial bus to transmit all the data.
This saves space in both the connector, and in the cable. It is also cheaper to install.
Personally, I think that there is no better bus for a student to start to learn how to inter-
face to external devices. It is relatively easy to build the interface electronics, and to connect
a few LEDs. How great it is to see a student's face after they have written their first program
to make a few LEDs flash on and off. I remember a third year student commented: 'I've been
programming for three years, and finally, we're doing something real.' Whether you agree
with this comment or not depends on the type of programming that you would like to do.
Some of us like doing databases, some like writing user-interfaces, but there are lots who like
to make computers sense things and make physical things happen. In the past, especially in
the 1970s and 1980s, electronic engineers used breadboards and wires to prototypes cir-
cuits. Sometimes the circuits blew-up, or times they would stop working, but at least you
knew where you were with the electronics. These days with massively integrated circuits, it is
difficult to know one end of a microchip from another. They normally work first time, they're
easy to connect to, and when they don't work you just throw them in the bin. Image the size
of the bin that would have been required if someone had had build a Pentium processor from
the discrete transistors (over 20 million of them). Image the heat that would have been gen-
erated. Assuming 15mW for each transistor, the total power would be 300kW, which is
equivalent to the heat given of by 3000 100W light builds, or 300 1kW heaters. So it shows
how far we have come in such a short time, as now we can touch the processor, and it just
feels a little hot. Personally, I would have no problems in going back to the days when tran-
sistors had three legs and a tin hat, and you had to look up a data sheet to tell which of the
legs was the base, and which was the collector.
So, as the technology has moved on, the parallel port seems like an old friend. It has
watched the PC develop as the inners have become more integrated and faster, but it has
never really been a high flier, preferring instead to quietly perform its duties without much
bother. From CGA and EGA to VGA, from the serial port to the USB port, from 5.25inch
floppy disks to 6550MB CD-ROMs, and so on. But, there's no way that the parallel port
could be allowed to stay as it was in the original parallel specification. It has potential, but
that potential is severely limited because it must always keep compatibility with previous
ports. So how is it possible to connect a printer on the parallel port, and other devices, with-
out the printer reading communications that are destined for another device. If it wasn't the
PC, the designers would have simply ripped up the original specification, and started again.
But, you don't do that with the PC, or you'll not sell. So, we'll see in the next chapter how
the parallel port has been dragged into the modern age. But, as we'll see, it's more like a
difficult toddler, than an enterprising businessman. The prize for the best upgrade goes to
Ethernet, which has increased its transmission rate by a factor of 100 (10Mbps to 1Gbps).
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