Track Sizes etc. (was Re: IBM 4331 (was Re: FPGAs))

Hi, Jay: As far as I know: IBM 2311 DASD had 3625 bytes per track, with 10 tracks per cylinder IBM 2314 DASD had 7284 bytes per track, with 20 tracks per cylinder IBM 3330 DASD had 13030 bytes per track, with 20 tracks per cylinder IBM 3350 DASD had 19069 bytes per track, with 15 tracks per cylinder I believe the use of the "portable" blocksizes, RECFM=FB,LRECL=80,BLKSIZE=3120 for source files, and RECFM=U,BLKSIZE=6144 for PDS load module libraries, came into widespread use with the introduction of the MVS IPO (Installation Productivity Option) -- IBM began distributing a pre-configured MVS system that could be easily installed and "up and running" quickly at new customer sites. This was introduced somewhere around 1978 to 1980, if I remember correctly. The idea was that the datasets on the IPO all had these block sizes, so they could be installed on most any popular DASD devices then available. This also became important of your worked for an ISV, and had to distribute your software on tape in a format that could be easily copied (restored) to disk at a customer site, with a minimum of fuss and bother. And, to address comments by Rich, responding to comments by Christian, as I recall, no operating systems then extant had yet come up with "a better way" to deal with "disk geometry" (as it was called). So, it was not only IBM operating systems that seem "primitive" by today's standards. AFAIK, it was not until FBA disks became popular, and in the 1980s, with the emergence of the SCSI standards, when companies began to figure out that it was much easier to just deal with a disk unit as a sequence of addressable blocks, and let the hardware (controller / device) figure out how to map that onto the actual drive "geometry". Also, it was not until the advent of SCSI that we really saw the emergence of the idea that devices (e.g. disk drives) could "identify" themselves, and tell the controller (or computer) about the drive size, etc. Actually, IBM invented much of this concept with the IBM System/38, which was designed starting around 1975, and that was first announced in 1978, but did not see widespread installations until 1980. With the System/38, all disks were formatted as "pages" of uniform size, and all "files" etc. reside in a vast virtual address space called "single level storage" where the objects themselves would actually be spread across multiple drives to gain the advantage of multiple heads and arms, to speed access to various parts of the objects. When you add a new disk drive to the System/38 (or the AS/400 follow-on product), when you power on the system, it detects the new devices, interrogates them to determine their capacity, etc., and then "auto-configures" them, so they are ready for use. So, the big change with the System/38, versus the IBM mainframes and System/34, System/36, etc., was that you never had to do a "SYSGEN" (or CNFIGSSP) to configure new devices -- you just plugged them in, and turned the system on. As far as I know, this was truly the first version of what would later be called "Plug-And-Play" (by Microsoft, circa the time of the introduction of Windows 95.) All the best, Mark S. Waterbury