[Simh] Origins of MSCP

[Paul Koning]

> On Jun 25, 2019, at 11:43 AM, Bob Supnik <bob at supnik.org> wrote:
> 
> True. My first assignment at DEC was managing the "New Disk Subsystem" (NDS) advanced development project, which led eventually to both the HSC50 and the UDA50. Among the goals of the project were
> 
> 1. To move ECC correction off the host and into the disk subsystem, so that much more powerful and complex ECC codes could be used.
> 2. To move bad block replacement off the host and into the disk subsystem.
> 3. To provide a uniform software interface for radically different disk drives.
> 4. To abstract away all device geometry information.
> 5. To implement command queuing and to perform all performance optimization, particularly seek optimization, in the disk subsystem.

#2 was only partially true in the UDA50 -- I remember an amazingly large body of code in RSTS for bad block replacement for the RA80 that's about 2000 lines of code -- roughly the same size as the rest of the MSCP driver.

I remember MSCP as part of the larger "Interconnect Architecture" effort, which produced a range of "interconnects" some of which seemed to become real and some less so.  There was the new peripheral bus (BI), the cluter interconnect (CI, computer interconnect) and one or two others.  I vaguely remember II (Interchip Interconnect) -- did that become I2C, or something else, or nothing?  And DI (device interconnect) ???  Also NI, which became Ethernet.  And XI?  I think we used that term in the networking group for the next generation high speed network.  Gigaswitch?  FDDI?  Not sure.  Part of the impression I had was that there was some overall concept unifying all this, but whether that was actually realistic is not clear.

One place it showed up was in the Jupiter mainframe (which didn't happen), supposedly built around CI and NI as its connections to the outside world.

There's also XMI, but that was a generation later as I recall.
	paul