IBM Mainframes

No it's not an Intel RAMdisk (on the left), though we'll just have to take their word for it that there is anything inside the box at all. Shoot, the box probably has gone to the scrapyard by now.

Cleaning out my files this morning I came across a notebook about the IBM 370 that I put together back in 1986 (!?!). I was working with a group in Phoenix that made their bones building RAM disks for mainframes using Intel RAM chips that only half worked. Intel couldn't, or didn't want to, sell these chips on the open market, but they had a bunch of them and they were piling up fast.
    Then someone realized that:

• mainframe computers didn't really have a size or weight restriction, 
• accessing RAM was much faster than transferring data to a disk, and
• while parts of Intel's broken RAM chips did not work, other parts did.

So they designed a circuit to use the working halves of the broken chips, designed and built big circuit boards, populated them with these broken chips and loaded the boards into big mainframe size cabinets.

    This business went great guns for a few years but by 1986 it was all but dead. This group of people had become experts in communicating with IBM mainframes, so they were looking around for a way to make use of that knowledge. The finally hit on making an universal adapter that would allow you to connect your Multibus I circuit boards to an IBM mainframe.

    They planned on selling a bunch of these things, so I got assigned to help out. I was there for a year. They sold a few, but the market never materialized. Since I didn't have much to do, I occupied myself reading about the IBM 370. Since IBM documentation was written by a bureaucracy, for a bureaucracy, it was not what you call concise. I pulled out what I thought was useful and drew up some tables to illustrate some of their more arcane features. When I left the group I put the notebook on the shelf.

IBM is still building and selling mainframe computers. They are no longer as large as a locomotive, now they are more the size of a couple of vending machines or commercial refrigerators. If you are nerd curious like me you can download all 1700 odd pages of the z/Architecture Principles of Operations, which seems to include the entire instruction set.

Also, while cleaning out my files, I came across a notebook of tedious details about Intel Multibus I computer systems. This notebook is now totally useless. I threw it out. Since IBM's latest processors are simply an outgrowth of the old System 360, my IBM notebook might still have some value. Now all I have to do is get it up on the net.