Differentiating Mainframes from Personal Computers

Mainframes, large and powerful computing devices, have some similarities to personal computers (PCs), but they also differ in some extremely significant ways. Comparing mainframes with PCs will help us understand the real power of mainframe computers.

Mainframes and PCs – A brief history
Mainframes were first developed in the 1950s. The first generation mainframes were extremely big machines requiring lots of floor space. But they delivered high-end performance compared to other computers of the time and were valuable to large-scale businesses. Over years, mainframes evolved into smaller, more sophisticated machines. Today they are very valuable to most large-scale data centers.

Personal computers, popularly known as “PCs”, evolved from mainframes in the late 1980s. They have the same basic components as mainframes: processors, memory, storage, operating system, input/output systems. Small and designed for individual users, PCs work efficiently in their purview.

Differentiating factors – Mainframes vs. PCs
The differences between mainframes and PCs far outnumber their similarities. Let us discuss some details.

Huge storage capacity: A PC typically has one or two hard drives with a maximum storage capacity of 500 Gigabytes (GB) to 1 Terabyte (TB), and 512 Megabytes (MB) to 4 GB of memory. Mainframe computers come with hundreds of hard drives having more than 30 TB of storage capacity. Mainframes require a minimum of 8 GB of memory to run.

Serve thousands of users: The name “personal computer” is accurate. A single PC serves a single user. One mainframe computer can serve multiple users, especially in large organizations.

High performance and speed: The average processor speed of a PC is 1.5 to 2.5 Ghz., and the RAM speed is around 1,500 Mhz.

A typical mainframe computer will have 3 times the bus speed and 10 times the cache speed of a PC. The speed of mainframes, combined with their ability to store and manage huge amounts of data, enables them to handle the large volumes of transactions necessary to large organizations like banks and government agencies.

•Higher I/O capabilities: While a PC handles input/output (I/O) of an individual user, mainframes handle the I/O requirements of thousands of users. They have much larger I/O bandwidth, and built-in redundancy and serviceability features. Thus they handle I/O functions much more efficiently than a PC.

Reliability: PCs suffer greater amounts of downtime than mainframes, due to the PCs’ lack of error monitoring and reporting tools. Further, PC operating systems need to be re-installed every few years, which is not only time-consuming, but also causes downtime.

Mainframes, on the other hand, are more reliable than PCs, with 99.99% uptime. This is possible because half of the hardware in a mainframe is designed for error detection. There are mechanisms to monitor every subsystem for potential failure. Further, the software applications on mainframes change less frequently. Though updates are made, the chances of downtime are less. These factors make mainframes incredibly more reliable than PCs.

•Size: The most obvious difference between a PC and a mainframe is their size. A PC can be 18-21 inches wide and easily carried in a briefcase.

Mainframes are not portable. They need floor space and are typically installed in temperature-controlled rooms. Compared to the first generation of mainframes, however, current mainframes are small and easy to maintain.

•Cost: PCs and mainframes are designed for different purposes. As their performance varies, so does their cost. A typical PC can be purchased affordably at a computer store. Mainframes are not available in stores at all, and they cost hundreds of times as much.

Though mainframes seem expensive, their functionality outweighs the cost. A mainframe performs the work of hundreds of PCs. It eliminates the need for large farms of PC in networks, and thus minimizes management, administration, and software-licensing costs.