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The 3081

A Complete History Of Mainframe Computing
By
The 3081

I still remember it like it was yesterday, that spring day in 1988 when I got a call from IBM telling me to come in to interview for a computer operator position. I was ecstatic when what was considered to be the greatest company in the world, the only one I wished to work for, was going to be my employer. It was a different time then, when IBM represented everything good about American business, and represented the pinnacle of success.

During my first day of work, I was introduced to a machine that was released in 1981, the 3081. I had some experience with an old Univac 1100/63 in college, but until then, I was more familiar with micro-computers, which were best represented by the still fairly-new 80386 and 68030. My first impression of the mainframes was unfavorable. Even by the microcomputers standards of the day, the interface was primitive and far less intuitive than that of PCs. I was not impressed.

The scale of things was shocking. The air-conditioned, raised-floor room was hundreds of feet wide and long, with almost a dozen 3081s and an enormous number of DASDs. We had six printers, which were enormous and almost the same size as the mainframe. There were three sets of consoles, one for the print area and one for the tape area, while the computers were monitored closely in the main console area.

We had three interfaces to MVS, as the operating system was called, which stood for multiple virtual storages, but we derisively referred to it as “man versus system.” There were the system consoles, which were essentially only available in operations: time share option (TSO) and operations planning and control (OPC). TSO was what many people used to do their work, while OPC was mainly for scheduling batch jobs that were going to run on the system. Many programmers preferred to work on VM, which was another operating system IBM offered for the 3081, before transferring their work to the MVS machine.

Our site had responsibility for the customer master record (CMR), which was used by many applications and sometimes directly by people. This ran on an IBM internal application called AAS, which was never sold. There were also some applications on CICS, which was the product IBM sold and is still widely used today by many companies. Many of these applications were critical, and any down time was extremely expensive during normal working hours. In fact, we were told that it cost IBM a million dollars every minute the system was down, which I never believed and still do not. Anyway, after these online applications would go down (usually at around 8:00 PM), the batch processing would begin. Jobs were scheduled in OPC and were submitted in kind of a "wrapper" called job control language (JCL). JCL could run several executables in one job and it specified the resources and order for the executables. You did not tell it explicitly in the executable which DASD to access, as the JCL defined where the input and output were. As mentioned, jobs were tracked in OPC, and were released based on time and/or dependencies. They were sent to the job entry system (JES) and from there were executed.

As mentioned, interfaces were poor compared to PCs of that time, but the reliability of the operating system was far greater than the Windows NT derivatives that we use today. It's something I learned to appreciate over time, and I still marvel at it. The 3081 was a "dyadic" design, meaning it had two processors that even shared the same cache. They could not be split into two computers, as they were inseparable. However, the sophistication of this operating system was such that even if one of the processors died, the system would stay up and continue to execute. The application that was using the failed processor would crash, but it would do so fairly gracefully as the operating system would recognize the failure and send it into the proper place for crashed applications (we'd track them in OPC, and either fix them ourselves or get their support team to take care of the problem). This is not to imply the 3081 CPUs were always crashing, as it was rare when they did so.

DASDs did fail fairly often, although most of the time failures happened when we had to power them down and then back up periodically. This was expected behavior and we always had CEs there for scheduled downtimes to repair those that were especially problematic. Normally, only one or two would fail out of the few hundred on the floor during each power down.

Each 3081 processor ran at a blistering clock speed of almost 38.5 MHz. By IBM's somewhat optimistic measurements, the base 3081 (model D) was up to 21 times faster than the 3033UP, while the higher-end model K was almost 30 times faster. Some of this, of course, came from the extra processor, although sharing the cache did create some overhead. The uniprocessor 3083, for example, actually ran 15% faster than the 3081 when the workload could not engage the 3081’s second processor. The 3084 was another extension of this line, and actually had a pair of dyadic processors. Unlike the 3081, it could be divided into two separate machines. Another improvement of the 3081 was that it could address more than 16 MB and used 31-bit addressing rather than the 3033’s 24-bit addressing. All in all, considering it was released only four years later than the 3033, it was a substantially improved machine. The hardware was good and the stability of the software was just incredible.

I hope the personal tone of this entry does not bore or irritate the reader, but I wanted to give a view of what working with these machines was really like. In many ways they were amazing machines. Still, as amazing as the 3081, 3083, and 3084 were, we were envious of sites that had the 3090, and we had heard the stories of how incredible the performance was.

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  • 12 Hide
    Ramar , June 26, 2009 7:39 AM
    Wonderful article, thanks Tom's. =]

    Killed a good hour of my day, and I very much enjoyed it.
  • 11 Hide
    pugwash , June 26, 2009 8:17 AM
    Good article, however although not quite "Complete". There is no mention of Collosus (which was used to break Enigma codes from 1944) or The Manchester Small-Scale Experimental Machine (SSEM), nicknamed Baby, which was the world's first stored-program computer which ran its first program in June 1948.
  • 10 Hide
    1ce , June 26, 2009 7:55 AM
    Really cool. One observation, on page 7 I think the magnetic drum is rotating 12,500 revolutions per minute, not per second....If my harddrive could spin at 12,500 revolutions per second I'm sure it could do all sorts of amazing things like flying or running Crysis.
Other Comments
  • -9 Hide
    seboj , June 26, 2009 6:50 AM
    Quote:
    Mainframes arguably express man's highest achievement


    But will it Blend?
  • 12 Hide
    Ramar , June 26, 2009 7:39 AM
    Wonderful article, thanks Tom's. =]

    Killed a good hour of my day, and I very much enjoyed it.
  • 10 Hide
    1ce , June 26, 2009 7:55 AM
    Really cool. One observation, on page 7 I think the magnetic drum is rotating 12,500 revolutions per minute, not per second....If my harddrive could spin at 12,500 revolutions per second I'm sure it could do all sorts of amazing things like flying or running Crysis.
  • 11 Hide
    pugwash , June 26, 2009 8:17 AM
    Good article, however although not quite "Complete". There is no mention of Collosus (which was used to break Enigma codes from 1944) or The Manchester Small-Scale Experimental Machine (SSEM), nicknamed Baby, which was the world's first stored-program computer which ran its first program in June 1948.
  • 2 Hide
    neiroatopelcc , June 26, 2009 9:11 AM
    So the ABC was in fact the first mobile computer? The picture does show wheels under the table at least :)  But I guess netbooks are easier to handle, and have batteries
  • 2 Hide
    dunnody , June 26, 2009 10:11 AM
    I am with pugwash - its a good article but why does it seem like it is a bit US centric, no mention of Alan Turning or "Baby" and the Enigma code cracking machines of Bletchley Park
  • 3 Hide
    Anonymous , June 26, 2009 11:47 AM
    Err what about the Zuse Z3?
  • 2 Hide
    candide08 , June 26, 2009 12:48 PM
    I agree with others, in that I am surprised that there was not even a mention of a Turing machine or other very early "computers".

    Surely they qualified as Mainframes of their times?
  • 2 Hide
    Anonymous , June 26, 2009 1:11 PM
    It's a shame that multiplication, addition and division benchmarks are not persistently noted throughout the article.

    I know that now a days it's very much dependent on software design, but it would still be nice to follow the progression in terms of calculation power of the machines.
  • 2 Hide
    theholylancer , June 26, 2009 2:05 PM
    25 pages??? i love ad block but damn this is annoying
  • 2 Hide
    vinnyny , June 26, 2009 2:20 PM
    Where can we get an 80/80 of this article without all of the noise? No PDF?
  • -4 Hide
    scook9 , June 26, 2009 2:27 PM
    So.....can it play Crysis?

    Out of curiosity, since its a metric I am more familiar with, what would the TeraFLOPS rating be in the newest and bestest from IBM. And how much would one of those bad boys set you back in the wallet.

    Was a very educational and interesting article.
  • 0 Hide
    lamorpa , June 26, 2009 3:04 PM
    "The 704 was quite fast, being able to perform 4,000 integer multiplications or divides per second. However, as mentioned, it was also capable of doing floating point arithmetic natively and could perform almost 12,000 floating-point additions or subtractions per second. More than this, the 704 added index registers, which not only dramatically sped up branches, but also reduced program development time (since this was handled in hardware now)."

    Many of these statements are sure to be wrong. 1) For sure, it would not be faster at floating point than integer. 2) Index registers have to do with memory addressing, not branching.
  • 7 Hide
    ta152h , June 26, 2009 3:33 PM
    First, I agree with the title being misleading, and I apologize for it. It was never intended to be a complete guide, which would be virtually impossible. I don't know why that title was chosen.

    The choice of computers was U.S. centric, because computers were U.S. centric. I chose only one mechanical computer, and it was made by IBM, since they were the dominant company. To add more computers would have been boring, and none of them were important technological milestones. So, while they might be specifically interesting to you, I was of the opinion too many computers from the same time frame would be boring. I almost chose the EDSAC over the EDVAC, but, went with the first design over the first implementation.

    With regards to the index registers, "the IBM 704 added index registers and a “TSX” instruction that would branch to an address but leave the address of the TSX in an index register. A single unmodified branch could use that index register value to return."

    Loops involve branching, branching involves memory addressing.

    With regards to floating point vis-a-vis integer, you need to be more careful about what you're sure of. For one, multiplies and divides are generally slower, being much more complex. But, more to the point, this information is available directly from IBM.
  • 1 Hide
    Anonymous , June 26, 2009 4:08 PM
    As one who live the mainframe era from the 2k machines for $500K...this story is incomplete without the story of the competition that was the force behind the commercial introduction at a furious pace of things we take for granted today.

    Any mention of mainframes without the Honeywell H-800 series, the H200 series or Multics leaves out systems that have had a large influence on computing as we know it. The H-800 was one of the first multiprocessing systems of the late '50s, the H-200 was Honeywell's answer to the 1401 in the '60s and Multics merely contributed much of the hardware architecture for the Intel CPU used in today's PCs and foreshadowed UNIX and many of the development tools we use today. I saw no mention of GE and their 600-6000 series. And NCR. (Remember the term "BUNCH" as the competitors to IBM.)

    So starting in the '50s, you should also have the history of the BUNCH woven in even to their demise. Not every great idea originated from IMB (though many did).

  • 2 Hide
    jackshaftoe , June 26, 2009 5:01 PM
    What, and no mention of Lawrence Waterhouse and his work during WW2??? :p 
  • 2 Hide
    Anonymous , June 26, 2009 5:10 PM
    Nice article, it was fun to review that history. I would have added mention of the groundbreaking Cray machines, especially the seminal Cray-1 (and it's successor X-MP) as the first "supercomputer." The X-MP looked like a futuristic chaise lounge with the main circuits in a center column surrounded by a circular padded bench. They were so arranged to reduce interconnecting wire lengths, as the speed was limited by the time it took electrons to travel through the interconnects...a speed of light limitation! The later Cray-2 was unique in that it was completely immersed in a bath of liquid Flourinert to cool the dense circuitry.
  • 2 Hide
    jsloan , June 26, 2009 5:38 PM
    the first computer programmers were all women!

    http://abcnews.go.com/Technology/story?id=3951187&page=1
  • 2 Hide
    aspireonelover , June 26, 2009 5:38 PM
    Great Article! I learned something new today! I've never been so "into" the computer history before.
    Thanks Rich Arzoomanian for writing this article.
  • 3 Hide
    jsloan , June 26, 2009 5:54 PM
    all jokes aside, this is the best tom's hardware article i have read to date. thanks for taking the time, effort and expense for putting it together.
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