RSX11M+
Veteran Member
- Joined
- Feb 14, 2011
- Messages
- 1,075
... evidently there was a major improvement in microcode efficiency between the KDF11 and the DCJ11, even without the increased clock speed and cache (again, if I'm reading this correctly!)
The improvement was indeed vast. Real experience gains of 2x to 10x could be attained by swapping an 11/23 CPU out for a J11 CPU - often without changing any other hardware.
Examples of this could be seen in our CAD PCB Layout system, and later on a VENIX based development system. Both were 11/23 CPUs swapped out for one of my KDJ11-A boards, before FPJ11.
- The CAD system was easily 3x as fast with the J11, and many operations were 4x. [I had to literally pry my CPU out of their hands to get it back]
- The VENIX system, was an older development system being abandoned in favor of 386/486 PCs for firmware development. Swapping it's 11/23 CPU for one of my J-11s resulted in so much improvement that there was a slight advantage to using the VENIX system over a department of PCs.
Ultimately, the PCs won out because of collateral reasons having to do with the "Networking" direction of the product line, and not the pure engineering tasks.
But it did cause re-evaluation.
These were both examples running on QBUS.
UNIBUS to QBUS comparisons tended to add an additional gain of 2x or more when the system was an 11/24. Our 11/24 based "Full Price" system was handily outperformed by the "Mid-Price" 11/23 system [based on a VT103] when a KDJ11 was installed instead of the 11/23.
Additional performance gains were attained by swapping system disk types for newer ones. [Same OS and product build]
We did do an amusing evaluation one evening that would have been completely absurd for most of our customers. We configured our "Full Price" system with it's UNIBUS video adapter on our 11/70 to take measurements.
The 11/70 with MASSBUS connected RM03s was 2x faster than the 11/73 with RQDX2 MFM disks. Moreover, the 11/70 showed almost no impact when "loaded" with traffic, as compared to the 11/73.
To this day, I would still like to perform this evaluation of that old system and software on a PDP-11 being emulated on a PC using SIMH or ERSATZ-11.
One of these days, I'll get around to it.