Compare and Contrast

Mainframes and Personal Computers

Jeremy Vigil

POS 355

Introduction to operating systems

Instructor

John Price

April 10, 2002

Overview

            Mainframes and personal computers have evolved over the years but their core functions have stayed the same.  The mainframe is used connect multiple users for large organizations while personal computers are generally used for a single users.  The more drastic changes for mainframes and personal computers have been speed and size.  Mainframes use to be the size of buildings.  Now they are the size of a textbook.  Personal computer’s origins came from the dumb terminal.  The dumb terminal was used just to access the mainframe.  Then, the idea came to off load some of the processing from the mainframe and place it on your desktop. 

Compare

The hardware is very similar between the mainframe and personal computer.  Their architecture has stayed the same over the years.  Only the complexity has changed but we have the same components.  They both have processors, storage, memory, operating systems, and displays.

They both have memory and hard drives to access.  Their operating systems optimize access for I/O because they have the same issue with I/O.  I/O is slow and time consuming so other processes are implemented while waiting for I/O to download. 

Over the last few years, mainframes and personal computers have become increasingly similar.  Mainframes were valuable tools because they can access more address space than a personal computer.  Less than ten years ago DOS had a memory cap of one megabyte.  Mainframes were able to access many times more than the DOS limit.  This helped batch processing for large corporations because batch processing needed more memory.  Speed was more valuable to them then cost.  Accessing megabytes of address space is no longer a sole benefit of a mainframe.  Windows 95 changed that for the personal computer.  In the future, there will be no difference between the personal computer and the mainframe.

Contrast

            Operating systems are different between the computer and mainframe.  The mainframe’s operating system is more complex.  This is for the multiuser support the mainframe provides.  Extra security and stability is needed.  Resetting a mainframe should not happen as often as a personal computer.  This is because a mainframe will affect hundreds to thousands of users. 

            The mainframe supports many users.  Multiple processors are needed to handle the extra load that mainframes receive.  Multiple processors are the standard for mainframes while it is only an option for personal computers.  This helps the mainframe's stability because a backup processor can be used in case of a failure.  This is also what makes the operating system more complex then the personal computer.  Stability is expected for the mainframe more than a personal computer.  The mainframe is also expected to run 24 hours a day 7 days a week.  This is why stability is so important with the mainframe.  The mainframe does not stop working when everyone goes home.  The cost of the mainframe encourages the users to use it as much as possible.

Conclusion

            Mainframes and Personal computers were drastically different when they were first introduced.  The mainframe took up buildings and the personal computer was only an interface to a mainframe.  Today, their similarities are growing.  Eventually we will not be able to tell the difference.  Has cost comes down for mainframes they to will become personal computers or an add-on to a personal computer for the price of a hard drive today.  Back in the day, mainframes were huge so I will conclude by saying it must be a mainframe if…..

You could kill someone by tipping it over on them, it's a mainframe. 

The only "mouse" it has is the one living inside it, it's a mainframe. 

You need earth-moving equipment to relocate it, or, it arrived in its own semi-tractor trailer, it’s a mainframe

You’ve ever lost an oscilloscope inside of it or, ever had a cardpunch designed for it, it's a mainframe. 

It weighs more than an RV, or has a power supply that's bigger than your car, it's a mainframe. 

Lights in the neighborhood dim when it's powered up or

Its disk platters are big enough to cook pizzas on, it's a mainframe. 

Keeping all of the manuals together creates a fire hazard, it's a mainframe. 

The operators considered the addition of COBOL to be an upgrade, it's a mainframe. 

It was designed before you were born, or the designers have since died from old age, its a mainframe. 

Its cables are thicker than your neck, it's a mainframe. 

Anyone has ever frozen to death in the room where it's kept, it's a mainframe. 

It’s so large that a dropped pen will slowly orbit it, it's a mainframe.   

Reference:

http://www.csuohio.edu/ist/Mainfrme.htm

http://www.mainframes.com/whatis.htm

http://home.ubalt.edu/tdarling/puad626_share/Vaskevitch/chap08.html