origins of IBM 3740 diskette format

"Michael Holley" wrote: I have been meaning to say all along this discussion - I thought they were designed to local microcode into 370's. That's the first time I saw one. It was stuffed inside a 370 and it had microcode on it. (I saw the service tech fooling with it and he showed me how it worked. But then I just *had* to find out what microcode was. Little did I know it would be like following Alice down the rabit hole :-) Can't remember what vintage that machine was. I think it ran DOS/VS and CICS. I do remember it had a giant refrigerator box of 3rd party memory which must have been all of 4mb. A 370/138 maybe? That machine ran 24/7 and was generally busy. heh. I remember I wrote a hack to submit little card jobs from the CICS terminals. It would freak out the operators because these jobs would appear in the print queue from space. I was quietly told to cease and decist by my boss :-) fortunately I discovered a dec-20 shortly after that. -brad