Fifty years ago, IBM unveiled the first System/360 mainframe, considered to be “the most important product announcement in the company’s history.” Despite the rapid pace of advance in the computing field, not only are mainframes still very much in use today, the launch of the System/360 introduced technical concepts that would become part of the fabric of modern computing.

As EnterpriseTech editor-in-chief Timothy Prickett Morgan writes, “that these virtual card wallopers are still around is a testament to the fact that software is sticky, that change is difficult or sometimes not worth the trouble, either technically or economically, and that gradual evolution is what makes IT products endure.”

The System/360 came to fruition after three years of development, under the direction of then IBM chairman Thomas J Watson Jr, assisted by chief architect Gene Amdahl, project manager Fred Brooks, and launch manager John Opel.

IBM invested two years of revenue into the project. As TPM writes, this was a gutsy and expensive undertaking, a bold move the likes of which is seldom undertaken by public entities. A project that was budgeted at $675 million – for factories, hardware and software development – ended up with a 1961 price tag of $5 billion (worth about $39 billon in today’s dollars).

The risk paid off handsomely, better than anyone could have imagined. Writes TPM: “IBM was breaking ground in so many new technologies, from chip manufacturing to software development, that it would have been hard to keep to the schedule and within the budget. The System/360 also turned IBM into a chip manufacturer on a large scale for the first time, and it also made the disk drives and reel-to-reel tapes that are visually synonymous with the mainframe in culture.”

In the first five years post-launch, IBM sold 4,000 of the mainframes and had orders for 20,000 more. It did not take long for Big Blue to recoup its extravagant initial layout. Profits grew by 20-25 percent per year in the late 1960s, dipping in the 1970s as peak demand dampened. At that point, IBM started pushing System/3 minicomputers, which ate into mainframe sales a bit. The result, writes TPM: “two healthy – although unfortunately incompatible – product lines, which incidentally live on as the Power Systems and the System z mainframe today.”

The 360 name reflected the machine’s general purpose nature. System/360 was intended for companies both big and small and for commercial as well as scientific use. The idea was radical, one machine that could span a wide performance range and could run the same operation system and application software to solve a wide range of business and scientific problems.

The System/360 also was revolutionary for another reason. IBM essentially merged its five product lines into one compatible family using an architecture that featured 8-bit byte addressing, which lives on in every computer today.

“After the S/360,” writes the company, “we no longer talked about automating particular tasks with ‘computers.’ Now, we talked about managing complex processes through ‘computer systems.’”

“It was the first product family that allowed business data-processing operations to grow from the smallest machine to the largest without the enormous expense of rewriting vital programs… Code written for the smallest member of the family had to be upwardly compatible with each of the family’s larger processors. Peripherals such as printers, communications devices, storage, and input-output devices had to be compatible across the family.”

The early IBM mainframes ran the performance spectrum from one to 50MHz. Memory ranged from a minimum 8KB up to 8MB in the high-end models.

While some view mainframes as old and outdated, 80 percent of the world’s corporate data is still managed by mainframes. Although the first model was revolutionary, today’s descendants are many times more powerful. Today’s largest mainframes can execute 52,000 business transactions per second. 40-50 new businesses every year get on a mainframe.

At a press event held in New York City today celebrating the half-century milestone, Steve Mills, IBM Senior VP & Group Executive, Software & Systems, ran through some of the highlights of the IBM mainframe 50 years after its introduction.

• 23 billion ATM transactions per year are processed by the mainframe, worth more than $1.4 trillion.
• $6 trillion credit and debit card payments processed annually.
• 3 billion travelers a year access mainframes in making their arrangements.
• 30 billion business transactions are processed daily.

Throughout the five decades since the mainframe’s debut, IBM has continued to emphasize compatibility. “Applications must continue to work properly. Thus, much of the design work for new hardware and system software revolves around this compatibility requirement,” maintains IBM. In cases where it cannot provide that backwards compatibility, IBM aims to give users at least a year’s warning that software changes will be required.