Den 2020-08-26 kl. 21:56, skrev Johnny Billquist:
The speedup of Massbus was also true in the "real world". I was dealing quite much with 11/750's, and both RM80 and RP06 were acting significantly faster than RA81. Probably did not have anything to do with the protocol itself, only slow RA81's :-)An interesting thing to observe is that a VAX780 simulator booting from anRM03 simulated device actually boots noticeably faster than the same simulator booting from an MSCP device. The I/O completion delays that were needed for the RP device were significantly shorter and involved fewer interactions than the MSCP (RQ) case.I am in a way a little bit surprised. While the whole interface to a massbus disk is much simpler than MSCP, it also exposes more of the hardware, and I would have expected MSCP to essentially not require any delays between request and completion. One of the nice things of the whole protocol design actually.
What Mark notice though may be because booting from a MSCP disk (on like a 750) initializes the controller which may take a second, but on Massbus disks it is instant.
-- Ragge