Creating new CP/M disks - Progress on IMSAI

[Allison]

>
>Subject: Re: Creating new CP/M disks - Progress on IMSAI
>   From: M H Stein <dm561 at torfree.net>
>   Date: Sat, 12 Jan 2008 14:37:42 -0500
>     To: "'cctalk at classiccmp.org'" <cctalk at classiccmp.org>
>
>-------------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
>
>> Date: Fri, 11 Jan 2008 23:50:27 -0500
>> From: "Richard A. Cini" <rcini at optonline.net>
> 
>>     Anyway, one of the issues I have with the Teac FD-55GFR (1.2mb
>> high-density; no schematic) drives Im using is that the motor runs all of
>> the time (just like an 8 drive) but these late-model Teac drives dont
>> have head relays, so the heads are engaged all of the time.
>
>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.

Really, I'll have to tell my NS* it doesnt work.. mine seems to like it.

>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.

Never seen one with it and I've seen and have at elast five differnt 
versions including one with a door lock.


Allison



>
>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
>