Vol. 2, No. 6 ------------------ < for cleo community> --------- November 1993


Note from the Editor

Installing A High Speed Modem

A Glossary .............................................Section 1/4

Why High Speed Modem....................................Section 2/4

"The Unknown"...........................................Section 3/4

What You Should Do.........................................Section 4/4

Notes from the Editor

@@@Ethio Science & Technology@@@ is a column presented to the Cleo community frequently. It covers various issues in the science; in particular, those of more related to Ethiopia. Your contribution is welcomed.

* For a couple of months I was not able to continue working on this column because of my own project which nearly suffocated me from participating at Cleo. Keeping my fingers crossed, I have resumed writing the column. In the mean time, the Cleo community at large should increase it's share of responsibility by participating in this and other formats.

* Today's column present my experience in installing a high speed modem to my PC. Why bring it to the Cleo community? I trust that most of you may have mastered doing it the right way from the beginning to the end, but there are some of us who perceive such task first as simple matter, but ended up with a headache as big as a planet Jupiter. The answer in short is to save a few sole.

A Glossary

MODEM For computers to talk to each other through a telephone line, they need a device the can allow them to communicate. This device is called MODEM. A modem converts a given electrical signals to an audio form of transmitable and vs. MODEM speed When a modem is said to have a capability of 2400 bps, it can transfer 2400 bits per second (bit is a single element of a Computer natural language.) But, this is not the same as "2400 baud" because the baud rate refers to a signal change frequency between two modems. If a single change frequency carry 2 bits, a 2400 baud modem can transfer 4800 bits per second.

UART chip UART (Universal Asychronous Receiver/Transmitter) controls the RS-232 serial port found in personal computers. A personal computer can only take advantage of high speed modem, if its UART is capable of handling high speed data transmission.

Why High Speed Modem

Suppose you want to transfer a file that amount to 1MB (1,048,580 bytes) from a computer located at Washington DC to another computer stationed in Addis Ababa.

Let's assume that both computers have 2400 bps modems. Can you imagine how long it takes to transfer such file? It is nearly about an hour. If we consider transmitting factors, the time might be longer. The slower the modem the longer it takes to receive or transfer data; as a result; the cost becomes expensive or hardly affordable. Especially, for Ethiopia, the poorest nation on earth, it may not be diner over a silver platter.

High speed modems have started crowding the market and the competition has grown ever enticing users to switch from low to high speed modems. Their prices are coming down faster than one can imagine. You can purchase just for $200.00 a modem with 14,400 pbs and built-in fax. A modem with 2400 bps may cost about $50.00 even for less if you are not quality-sensitive.

"The Unknown"

If you buy a 2400 bps or lower speed modem, you can place it into your computer using the open slot. Once, you install the communication software you are in business. Well, would it be the same thing for higher speed modems? The answer depends on the speed you want to have and the type of computer you own. If you want to limit yourself to 2400 bps or less, the above statement is true for a modem with 14,400 bps. The irony is that you bought a high speed modem wanting to transfer a large file with in short period, but you are unable to use this potential. The money you spent is laughing at you! Why such problem arises?

Most personal computers if not all come with a chip which is called UART (Universal Asynchronous Receiver/Transmitter). UART controls the RS-232 serial port which is used by personal computers to transfer data one bit at a time. Unfortunately, the UART that are found in most personal computers are 8250B. This type of chip is not capable of handling high speed transmission. If you try, you will face all kind of unworthy experience. When you buy a high speed modem, unless you ask for it, a lot of venders fail to tell you that your UART may not permit high speed transmission. It happened to me and to also a friend of mine.

What You Should Do

Before considering to buy a high speed modem, you should really examine why. Possible reasons may be:

1. You are up-loading and down-loading a lot of files

2. You are using your home computer to connect you to school's computers

3. You are sending or receiving a large mails through electronic mail

4. You are running your own bulletin boards and so on...

If you decide to buy a high speed modem, your next step should be knowing your computer components that are related to modems. In particular, you must find out what kind of UART your computer has. It is also worthwhile to check that your computer has an open slot so that you can buy an internal modem. If not, you may use one of your serial port which can be plugged to an external modem. All these fail, you may be out of luck.

There are several named brand modems available in the market. I bought the AT& T dataport 14,400 pbs, which so far has not given me any problem. In addition, it has a life time warranty from AT& T. Wowwwww! There are other good modems out there. If your personal computer has UART 8250B, you must replace it with the UART 16550. There are two ways of doing this:

1. If the UART chip is stand alone on the motherboard, you can buy just the chip for less than $30.0 and replace it yourself. Note: Please, you should know what you are doing when you upgrading the system.

2. There are 16550 UART-based multi-Input/Output cards. One might cost about $80.00. You can insert the card into one of the open slots. In case, if the card has ports, carefully you need to disable either the card or motherboard's.

I hope you don't have to go through what I had. After I order the modem, it took 4 weeks to arrive and about a week to learn and find out about UART. Then I had to wait about 11 days to get the right UART chip. Finally, I was able to install the modem into my personal computer. I never thought it would be that cumbersome.

--- Cheers


Abass B. Alamnehe /

abassa@neosoft.com /