32-Bit Computing: What's It All About?

John Rusnak, Athena Consulting
Lee Ridgway, Publication Services

In the whirl of Windows 95 (Win 95) publicity, you may have heard 
references to 32-bit computing. This term is worth understanding, since 
32-bit hardware and software is becoming the standard for desktop 
computing. This article gives an overview of 32-bit computing and its 
advantages, and discusses Microsoft's strategy with respect to Win 95 
and Windows NT.

What Does 32-bit Mean?
A binary digit, or bit, is the smallest unit of data that a computer 
can process. All other things being equal, the more bits your computer 
can process at the same time, the faster it is.

Most desktop computers manipulate bits in groups of 16 or 32. If you 
have two computers whose clock (processing) speed is identical, and one 
processes 32 bits at a time while the other processes 16, the 32-bit 
computer will be about twice as fast.

Makeup of a 32-bit System
Computer hardware that is 32-bit-capable can move data in 32-bit 
groups. This includes transfers between the central processing unit 
(CPU) and connected devices. To take advantage of these 32-bit features, 
though, you need a 32-bit operating system and 32-bit software. 
Microsoft's Win 95 and Windows NT, IBM's OS/2 Warp, and Apple's 
Macintosh System 7 are all 32-bit operating systems (although there are 
some qualifications with respect to Win 95 that will be discussed 
later). Vendors are now releasing 32-bit versions of application 
software for Win 95; 32-bit application software already exists for 
Windows NT, OS/2, and Macintosh System 7.

Advantages
One advantage of 32-bit systems is speedier processing for resource-
hungry applications such as math packages, graphics and publishing 
programs, and network operations.

In addition, when a machine's internal addressing scheme uses 32 
bits, it can address much larger amounts of memory and hard disk space.

Yet another advantage of 32-bit systems is faster multitasking, where 
two or more applications run at the same time. An operating system 
performs multi-tasking by sending different parts of many tasks to the 
CPU at different times. Of course, the faster the system, the less 
likely it is that the user will notice what's going on behind the 
scenes.

Cooperative versus Preemptive Multitasking
In addition to speeding up multitasking, many 32-bit systems offer 
preemptive multitasking. This represents an important advance over 
cooperative multitasking, which has been the norm for most desktop 
computers. Here's how the two differ.

With cooperative multitasking, the operating system gives control to 
an application and it is the application's responsibility to release 
control. When it does, the operating system can give its attention to 
another application.

Some programs "cooperate" better than others by giving up the CPU at 
the most opportune times. Some poorly written programs hardly ever give 
up the CPU. So with cooperative multitasking, a wayward program can 
monopolize your machine and even bring it to a halt.

With preemptive multitasking, the operating system decides which 
application will receive control of the CPU and when it will release 
control. This leads to a more orderly sharing of system resources among 
multiple programs.

The Scoop on Windows 95
It's clear that 32-bit systems are better than 16-bit systems - 
they're faster, can address more memory and hard disk space, and usually 
offer preemptive multitasking. And Win 95 is 32-bit, right?

Not entirely. Win 95 has been designed to run both 16- and 32-bit 
applications, and to do so on machines with as little as 8MB of RAM. To 
do this, Win 95 includes some code from Windows 3.1, a 16-bit operating 
system.

The good news is that you should not have problems when running 32-
bit applications exclusively. Running 16- and 32-bit applications at the 
same time, however, may degrade performance, due to the different ways 
these applications handle multitasking.

Windows 95 or Windows NT?
In the best of all worlds, Microsoft would market only Windows NT, an  
exclusively 32-bit operating system. Windows NT is a much more powerful 
and robust operating system than Win 95. However, Windows NT has 
steeper hardware requirements (see the chart below) and it can't run 16-bit 
applications. For now, Windows NT is seen as a system for advanced 
users, particularly in networked and client/server situations.

Win 95 is positioned between the 16-bit Windows 3.x and the 32-bit 
Windows NT. Most Windows 3.x users will find that, when the time is 
right, moving to Win 95 will give them most of the advantages of a 32-
bit system, while retaining compatibility with 16-bit applications. In 
addition, many won't need to upgrade their hardware in order to run 
Win 95.

Hardware Requirements
The chart below summarizes the architecture, minimum recommended 
RAM, and free hard disk space needed for various operating systems. 
Numerical ranges are given to allow for different hardware configurations 
and installation choices. For the PCs, a 486 or higher processor is 
recommended.

Getting Help
If you want help choosing an operating system for your PC, contact the 
Microcomputing Help Line at x3-0001 <micro-help@mit.edu>. You may also 
want to attend some user group meetings (see pp. 1-2), and talk to 
members about their experiences and preferences.

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                                                Minimum         Hard Disk  
Operating System        Architecture            RAM (MB)        Space (MB)

Windows 3.1             16 bit                  4               6-10

Windows 95              16/32 bit               8-16            10-70

Windows NT              32 bit                  12-20           90-120

Windows for             16 bit                  4               3.5-19
  Workgroups

OS/2 Warp               32 bit                  4               35-50

Macintosh System 7      32 bit                  4-16            15-25