-------------Original Message: Date: Sat, 12 Jan 2008 09:37:06 -0800 From: "Chuck Guzis" <cclist at sydex.com> Subject: Re: Creating new CP/M disks - Progress on IMSAI Since the 8272/765 does drive "polling", you have to connect DRIVE SELECT/ to DRIVE SELECT/. Connecting it to MOTOR ON/ would likely have some odd effects. Recall also, that the 765 can do overlapped seeks on multiple drives, which requires that the DRIVE SELECT/ line be what it says it is. Which leaves you with connecting HEAD LOAD/ to MOTOR ON/; not a good solution if you do a lot of multiple-drive operation (as CP/M floppy systems are wont to do). Better would be to use a timer to monitor the HEAD LOAD/ line and keep MOTOR ON/ active for a minute or so after the last drive activity. A (or a couple) of NE555's should do the trick. Recall that with the 55GFR, as the drive will not gate INDEX/ pulses until it's determined that the diskette's come up to speed. (This, BTW, is why hard-sector diskettes don't work in a 55GFR). So if you'r getting INDEX/ pulses, the drive, by definition, is ready. That's not to say that you couldn't get a GFR with a head-load solenoid, but they're pretty uncommon. My take anyway. Cheers, Chuck ----------------Reply: That was going to be my last-ditch suggestion for the TEAC, putting a one-shot delay on the /MOTOR ON line (Chuck, you know how I love 555s ;-). That delay on the 55GFR is not only a problem with hard-sector diskettes; when I went through this exercise replacing 8" drives on my Cromemcos (soft-sector), the GFR didn't work because the /DS -> /READY delay was too long, even with the motor spinning. Tying /READY to ground made it work and I suppose one could tie /READY to /DS with a diode if one had no other drives available. Interestingly, Andrew Lynch apparently got a different version of the GFR (-149 IIRC) to work on his Vector with HS disks, whereas my -159 never goes ready at all with HS disks. The YE YD-380 does have a HL solenoid but AFAIK it's not separately controllable; there's a pair of jumpers (HM & HS) that select whether the head loads on /MOTOR ON or /DS. Nevertheless, it's probably the closest to an 8" drive with a HL solenoid and constantly running motor. One thing I've learned from trying to use 1.2Mb HD drives in anything other than an AT is that among the dozen or so drives I tested there's almost no consistency at all as far as jumper options and labelling, /READY and /INDEX logic, etc. are concerned, even with different versions of the same make and model. One of the most adaptable drive in my limited experience has actually been the Panasonic JU-475 FWIW. mike