> On Jun 24, 2019, at 5:27 PM, Timothe Litt <[email protected]> wrote:
>>
> As is often the case, things turn out to be complicated. Here's a more
> detailed version. In an off-list note, Bob pointed out that MSCP originated
> in a project he managed that was to develop the "next generation" disk
> controller - a forerunner of the UDA. ...
> However the similarities came to pass, I found viewing DSA as an evolved
> Massbus to be a useful model, with a lot of support for that perspective in
> the specifications. MSCP contains the high-level protocol of Massbus drivers
> (and much more) through the drive control logic/formatter. SI replaces the
> DCL/formatter to drive "bus" of Massbus -- SI is serial, ruggedized and
> capable of quite long runs. But it carries much the same low level drive
> commands. (Note that there's a long history of serializing parallel buses as
> technology evolves, e.g. PCI -> PCIe -> CSI, a.k.a. quickPath). The host
> ports (UQSSP,KLIPA,etc) replace the registers and DMA channels. Command and
> function names from Massbus spec & drivers often appear in the MSCP spec
> versions that I used...
Very interesting. I never thought of MSCP as a descendant of earlier DEC
storage architectures. Perhaps because all I really saw was what the UDA50
exposes, which from the programmer's point of view is radically different from,
say, the RP04 or RK05.
On the host ports and message based I/O, that same approach appears earlier in
the KMC11 and its derivatives such as the DMC11 network controller. Were those
an influence on the message based host port design?
paul
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