The May 1989 issue of Capital District T/S Computer Club’s newsletter told of two members using T/S2068’s with LKDOS having trouble reading each other’s disks. It seemed that Fred Lewis could read John Warren’s disks but John could not read Fred’s disks. This sounded familiar to me as I once had trouble reading disks that came from Rod Gowen and Larry Kenny.
The problem I had was head stepping rate. The drives I use have a 30ms stepping rate. This means that to move from track 0 (the directory track) to track 40 requires 1.2 seconds. A 6 ms stepping rate requires only 240ms. What the controller chip does is wait a period of time to begin reading or writing the disk to give the head time to get to the desired track! The information for the stepping rate is placed in track 0 when the disk is FORMATed.
There is no problem reading the directory track because the head starts there, but the head on John’s drive is not yet over the correct track when the controller tries for the read. For this reason John Warren could not read Fred Lewis’s disks. Fred either has a newer controller chip or has drives with a 6 ms stepping rate and FORMATed his disks accordingly.
I could not read the SYSTEM disk that Larry Kenny sent me. Larry had not run into the slower drives up to that point. Mine are DEC dual drive units using TEAC drives purchased in the early 80’s as a group buy and are so reliable I just won’t give them up.
Larry was sure he had the answer when I phoned him and to get me started back in February of 1988, he sent a program to the club BBS at 2 AM while I slept to fix his disks so that I might read them. I tried it and it worked! I re-wrote it and called it steprt.B1 The stepping rate information is in track 0 and his program fixes the disk to the 30 ms stepping rate.
Now about controller chips, Larry stated that he started using the new Western Digital chips that could only select 6 ms or faster head stepping mechanisms. I told him, each time I ordered, to send me only the old WDC WD1770 controller chip in units he built for me and my friends as over 200 of these TEAC units are in the area and we all want to be compatible.
When passing around disks for the LarKen disk operating system be sure they are formatted single side 40 track with a 30 ms head stepping rate so we all can read them.
To read unreadable disks, just load in the program below, it will autorun. After removing the write protect label from the faulty disk, place it into DRIVE 0 and press <ENTER>. Follow the instructions and you will be able to read it from then on. I have tested it on LARKEN and RMG disks.
100 REM STEP RATE CHANGER BY LARRY KENNY and BOB SWOGER V2.1 for the LARKEN DSK-400 system
110 REM Written and placed in the public domain by Bob Swoger
120 REM Use to change the head step rate on Track 0
280 CLEAR 39999
290 BORDER 1: PAPER 1: CLS
300 PRINT AT 2,4; INK 2; PAPER 7;"LARKEN DISK UTILITY v2.1"; PAPER 1;AT 4,4; PAPER 2; INK 7;" Head Step Rate Changer ";AT 6,5;" © 1988 Robert Swoger "
310 INK 7: PLOT 0,108: DRAW 0,62: DRAW 255,0: DRAW 0,-62: DRAW -255,0
320 INK 7: PLOT 8,114: DRAW 0,50: DRAW 238,0: DRAW 0,-50: DRAW -238,0
1010 REM MC STEP RATE CHANGER BY LARRY KENNY OF LARKEN ELECTRONICS V1.0
1020 PRINT AT 10,0;"The head step rate is importantfor proper operation of the diskdrive.";''"Too fast and others may not beable to read your disks.";''"Too slow and your drive may purrwhen moving from track to track.": INPUT " Press ENTER when ready >"; LINE p$
1025 PRINT AT 10,0;"The LarKen DSK-400 Floppy DiskInterface presently comes in twoversions. Version - L3 uses aWD1770 controller chip and canhandle head stepping rates of6, 12, 20 and 30 mS. Version L3Fuses a WD1772 controller chipand handles the newer and fasterdrives with head stepping ratesof 2, 3, 6 and 12 mS.": INPUT " Press ENTER when ready >"; LINE p$
1030 PRINT AT 10,0;"If your system is Version - L3and you wish to send disks toothers using versions A3, L3, O3or R3, use the 30 mS step rate.If you send a disk to users ofversion L3F, use the 12 mS steprate. This may mean that you canno longer read or write to thatdisk. If you receive a disk thatmakes your drive 'purr' then runthis program to fix the disk foryour particular head step rate.": INPUT " Press ENTER when ready >"; LINE p$
1035 PRINT AT 10,0;"This program changes the headstep rate on track 0. Head steprate is the minimum speed in mSwhich a head stepping mechanismcan travel to get from one trackto the next. Remove the writeprotect label, place the diskwhich needs its head step ratechanged into DRIVE 0 and pressENTER. "
1040 INPUT " CONTINUE ? "; LINE p$: IF p$<>"" THEN IF p$(1)="n" OR p$(1)="N" THEN GO TO 9998
1050 INPUT "Head speed 2 3 6 12 20 30 mS?"; LINE p$
1055 IF p$="q" OR p$="Q" THEN STOP : GO TO 9998
1060 IF p$="2" THEN LET p$="20"
1065 IF p$="3" THEN LET p$="30"
1070 IF p$<>"6" AND p$<>"12" AND p$<>"20" AND p$<>"30" THEN GO TO 1040
1075 LET s=INT ((VAL p$/6))-(1+(p$="30"))
1080 RANDOMIZE USR 100: GO TO 0
1090 RESTORE 1150
1110 FOR A=40000 TO 40030
1120 READ B: POKE A,B
1130 NEXT A
1140 REM THE s IS THE STEP RATE
1150 DATA 243,205,98,0,175,50,29,32,205,126,0,205,123,0,62,s,50,134,32,205,120,0,58,100,0,251,201,0,0,0,0
1240 PRINT AT 20,12; FLASH 1;"WORKING!"
1250 RANDOMIZE USR 40000
1260 PRINT AT 20,12; FLASH 1;"Finished"
1270 REM GO TO 9989
1280 GO TO 9998
1360 FOR B=40000 TO 42000: PRINT PEEK B;",";: NEXT B
9989 RANDOMIZE USR 100: GO TO 4
9992 RANDOMIZE USR 100: SAVE "steprt.B1" LINE 100
9993 REM RANDOMIZE USR 100: SAVE "steprt.B1" LINE 100
9998 RANDOMIZE USR 100: LOAD "L.B1"