On 10/13/2015 5:08 PM, Jay West wrote: > Pictures of the S/130 system I'm building up are at > https://www.flickr.com/photos/131070638@N02 > > I think the last I posted here... the cpu was up and running, that was the > first piece I refurbished. I took everything out of the rack and cleaned > that up well, and the cpu has been remounted there. > > Yesterday I mounted the 6030 dual 8" floppy drive. It was squeaky clean > inside and at power up everything does what it should. However, I can't > proceed further with it as I have no media. The docs say it uses hard sector > 8" floppies, which I believe I can find. However, it specifies 8 > sectors/track hard sector floppies - and those I've never heard of. Maybe DG > made them special just for their gear, or, maybe the drive or controller or > software was smart enough to expect the more common 32 hard sector floppies > and knew to only pay attention to every 4th sector hole ;)
I see that sector count (0-7) in the 6030 technical reference. But all of the HS floppies I have for DG are 32 sectors - and many of those are software distribution floppies for Novas, appropriate to the 6030. They are all labelled DG Diskette (as opposed to /2, /3 or /4), as per the illustration in the 6030 manual. SO: The manual specifies a max sector access time of 166ms, and a min of 1.2ms. 166ms implies a rotational speed of 360 rpm (6 revolutions per second, or 166ms). Divide that by 8, and we get sectors about 20ms apart (8 sectors), with an extra index pulse 1/2 of that, or 10ms. For 32 sectors they would be at 5.1ms and the extra index pulse would be 1/2 of the 32 sector pulse, or 2.6ms. Looking at the schematic I have, 001-000797-10 (rev 10), sheet 2, bottom left quadrant, the index pulse is fed into a one-shot with a time constant noted of 3.9ms to generate the index pulse - which would be pretty darn close to 1/2 of the way in between 2.6ms and 5.1ms. The sector pulse is derived from a counter, U63. The counter has an input signal labelled "DIV 4" to pins 5 and 6. Also (this would have saved time had I seen it right away) there is a timing diagram, 001-000893-00 that shows 5.2ms between sector pulses, and 2.6ms for the extra index pulse, with pulses being 1.1ms in length and also shows the 3.9ms one-shot timing. That cinches it: the design is for 32 sector floppies. More to follow related to my hardware and software inventory, but I just got called to dinner. JRJ
