On 11/22/19 1:01 PM, Paul Koning via cctalk wrote: > >> On Nov 21, 2019, at 10:13 PM, Chris Zach via cctalk <[email protected]> >> wrote: >> >> I *think* (and this is putting the wayback hat on) that the RH11 originally >> was the controller for the RS03 and RS04 fixed head disk drives. The dual >> Unibus was so you could put them on Unibus A for talking to the 11/45's main >> bus with data transfers ripping across Unibus B directly to the dual-ported >> memory on the 45. >> >> Thus one of the Unibus ports didn't need to worry about arbitration (it was >> the only thing on the bus) and could stream data from the (very quick) >> RS03/04's right into memory for the ultimate swap device. > Nice swap device, certainly. But the RS04 isn't actually all that fast. The > book says 4 microseconds per word, compare that with the RP04 at 2.5 > microseconds per word. I remember we got an RP04 on our college 11/45 in > 1974 or early 1975, but that one still had an RF11 swapping disk. So it's > not clear to me which came first. But being a fixed head drive, the RS04 has no seek latency, so probably faster overall than a moving head drive.
We had an RS04 swap device on our 11/70 at Purdue Electrical Engineering Network running BSD Unix. It had been running for so long that the disk/head lubricant had worn away. If it was ever spun down, it would have to be hand spun to overcome the initial friction, but then it was fine. --tom >> The 2020 takes advanatge of this with the dual unibus adapter, one talks to >> the chatty stuff like the DZ11's, the other has no arbitration issues as it >> sucks data down from the faster spinning RM03s without timeouts. > RH11 machines could use the RM02 but not RM03; that one was supported only on > the 11/70 because of its speed. But it's way faster than these other disks > we mentioned. And then there was the RP07, which was never officially > supported on any PDP11 even though it did work fine on an 11/70; it was the > "super large" disk on the main RSTS/E development system. > >> One of my long term questions has been to see if a 2020 could talk to a >> RM80. It should be possible as the Massbus personality module talks to the >> bus at 3600 RPM just like the RM03, and they did manage to get the R80 to >> talk to the 11/730 with a dedicated memory channel connection (though maybe >> the R80 was heavily interleaved) > If it can handle an RM03, then I'd expect an RM80 should work also since it > transfers at the same speed. > > paul > >
