polling / interrupt
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From: Gavin Scott on 7 Jun 2010 20:15 Rick Jones <rick.jones2(a)hp.com> wrote: > Going-back farther, there was the "DTC" (aka Avesta) on the PA-RISC > HP3000's (and used with the HP9000s) - all that ugly slow serial stuff > was put out into the DTC and it was linked with the host via a (by > then standards) blazing-fast 10 Mbit/s Ethernet link. The X.25 > functionality wsa offloaded into that thing too. > Trouble was, there ended-up being an entire networking stack for > talking to the DTC... Which as I recall was one of the major causes of the late shipment of MPE/XL 1.0. After building all this wonderful networking code to implement the whole OSI layered protocol stack thing, it took just around one bazillion instructions executed to process a single user keystroke arriving from the DTC. After certain intensive optimization efforts this was reduced to something like 1,000 instructions and life was good and the DTCs ended up being a perfectly fine way of connecting slow serial devices (terminals and async printers) to the system. I recall someone telling me at one point in later years that the MPE/XL people were envious of HP-UX's monolithic drivers and their better latency, while the HP-UX guys were envious of MPE/XL's more modular approach and the flexibility it gave, each wondering if maybe they should have taken the other's course. G.
From: Rick Jones on 8 Jun 2010 13:50
Gavin Scott <gavin(a)allegro.com> wrote: > I recall someone telling me at one point in later years that the > MPE/XL people were envious of HP-UX's monolithic drivers and their > better latency, while the HP-UX guys were envious of MPE/XL's more > modular approach and the flexibility it gave, each wondering if > maybe they should have taken the other's course. Sometimes they were the same people just at different times :) rick jones -- A: Because it fouls the order in which people normally read text. Q: Why is top-posting such a bad thing? A: Top-posting. Q: What is the most annoying thing on usenet and in e-mail? |