"Robert_L._White.ESXC15"@XEROX.COM (07/22/88)
Hi, I just FTP'ed the schematic for the step doubler. Program 40_80_tr.pi3 I have some questions though. 1) what exactly does this do? i.e. does it double the step pulse from one pulse to two pulses, or lenghten the step pulse. 2) must you use a hi density 5.25 (1.2 meg) to use the 80 track feature? I didnt think the standard 5.25 that an IBM uses would do 80 tracks. I currently have a 5.25 hooked up, but have several problems. I have changed the memory locations required to make the step pulse 6ms but still I have problems. The problems are: 1) I cannot format the 5.25 under pc-ditto 40 track, it fails. The drive seems to do a lot of stepping. 2) I have written a "c" program to format for 40 tracks, and that works with no problems (no errors returned), except that I get allot of disk errors when reading or writing. i.e. data on disk may be damaged, cancel,retry. Sometimes a retry will work, but not allways. 3) The really strange thing is, when I format a 5.25 on a PC, I have no problems reading or writing to that disk on my 5.25 drive on my ST. Wierd! Any help would be nice Thanks Bob White, Xerox corp.
med@druhi.ATT.COM (Myron Drapal) (07/23/88)
In article <880721-140208-4503@Xerox>, "Robert_L._White.ESXC15"@XEROX.COM writes: > The problems are: > 2) I have written a "c" program to format for 40 tracks, > and that works with no problems (no errors returned), > except that I get allot of disk errors when reading or > writing. i.e. data on disk may be damaged, cancel,retry. > Sometimes a retry will work, but not allways. > 3) The really strange thing is, when I format a 5.25 on a PC, > I have no problems reading or writing to that disk on my > 5.25 drive on my ST. Wierd! > > Any help would be nice > Thanks > Bob White, Xerox corp. In order to get most (if not all) 5.25 inch drives to work consistently on the ST, you *must* buffer the drive selects (a and b) and the side select signals from the ST. They are driven (poor choice of words ;-)) by the wimpy GI sound chip, which can barely drive the 10 inches of cable, let alone the inputs of the drive. Also, make sure to remove the termination (try this first, it may be just enough to make it work). If you set the two undocumented seek rate varaibles, and do this buffering (non-inverting, I think a 74244, but look it up first), you should have no problems. Myron Drapal AT&T Denver ihnp4!druhi!med
hase@netmbx.UUCP (Hartmut Semken) (07/26/88)
In article <880721-140208-4503@Xerox> "Robert_L._White.ESXC15"@XEROX.COM writes: >Hi, I just FTP'ed the schematic for the step doubler. >Program 40_80_tr.pi3 >I have some questions though. > 1) what exactly does this do? i.e. does it double the step pulse from > one pulse to two pulses, or lenghten the step pulse. To make a 80-track drive read 40-track-PClone disks, it produces 2 step impulses from one. > > 2) must you use a hi density 5.25 (1.2 meg) to use the 80 track feature? I >didnt think the standard 5.25 that an IBM uses would do 80 tracks. There are 80-track-dd-drives. The "standard IBM" uses 40-track-dd like Teac 55B. The Teac 55F is exactly the same as the 55B, except for the head (the 80-track type writes smaller tracks) and one resistor (for internal doblestepping). If You connect an 80 track drive (beware of the pullup resistors and so on) *without* a step doubler, it "looks" like an 3.5" to the ST; the interface Sony used for their first 3.5" drives is the 5.25"-Shugart BUS. The HD drives the AT uses are 8"-look alikes (to the controller chip); they were chosen because of their speed, which is 500 kbit per second (versus 250 from a 5.25" drive/interface). The extra capacity was a neat bonus. Most HD drives can "fallback" to 80 track double density, for unformatted 1 megabytes or 720 KBytes with IBM-format. The AT software (BIOS) does not handle this format. With double density the AT-Bioses use double stepping to read 360 Kbyte (40 track) disks. > > >I currently have a 5.25 hooked up, but have several problems. I have changed the >memory locations required to make the step pulse 6ms but still I have problems. > >The problems are: > 1) I cannot format the 5.25 under pc-ditto 40 track, it fails. > The drive seems to do a lot of stepping. > 2) I have written a "c" program to format for 40 tracks, and that works >with no problems (no errors returned), except that I get allot of disk errors Maybe that PCDitto does another doublestep (quadrostep alltogether) when formatting 40 tracks. Try do disable you step doubler. Or PCDitto does not use the TOS-step rate code ans steps with 3 msec. Ask the authors of PCDitto. I hops this helps a little hase -- Hartmut Semken, Lupsteiner Weg 67, 1000 Berlin 37 hase@netmbx.UUCP High on a rocky promontory sat an Electric Monk on a bored horse. (D. Adams)