Can an 80-track drive read 40-track floppies?

[oktology]

I know in some PC setups a 80-track drive can double-step to read 40-track floppies. Can a TRS-80 (specifically a 4P) do this?

 

[krebizfan]

I thought the TRS-80 Model 4P generally had only 40 track drives so it wouldn't need to double step. Are you planning on trying a quad density setup in the 4P? That would include using high density drives set to 300 RPM. Someone with more knowledge of the OSes would have to answer if any version included double step. 80 track was possible but the setups I have seen included a 40 track drive in addition to the 80 track drives.

Some drives did have jumpers that would force them to double step. I have never understood why since one would have all the problems of 40 narrow tracks without the option of storing 80 tracks on the disk.

 

[Eudimorphodon]

I’m reasonably sure that some TRS-80 DOSes had support for double-stepping 80 track drives for data transfer, but I’m thinking of third-party Model I and III products like Newdos 80. There’s a lot less diversity in Model 4 DOSes, so I would suggest checking the LS-DOS 6.3 manual and seeing if it’s mentioned at all. (You could also check the Model I/III LDOS manuals, I think the disk config options are largely syntax identical. Since Radio Shack never sold 80 track drives they might have left details out of the TRSDOS 6 manuals despite it being based on LDOS.)

Do you have a Model 4P with 80 track disks installed?

 

[Trash-Eighty]

With NEWDOS/80 V2.0 double stepping can be specified by the PDRIVE command. The parameter TI has some optional flags which could be set.
From the manual:

Flag L means two step pulses between tracks. This allows a 35 or 40 track diskette to be read on an 80 track drive. Writing can also be done in this manner, but the 35 or 40 track drives have trouble reading some of the sectors so writing is not recommended.

 

[ldkraemer]

The Model 4 running Montezuma Micro Ver 2.31 CONFIG command will allow you to select the type
of floppy Drive, along with the stepping rate you want for the Physical Drive. You can also select
the Floppy Definition that is included in file "DISK.FDF".

These parameters can be either temporary, or permanent on the Boot Floppy.

*Access Matrix (40T, SS, DD, 171K)
36,3,7,0,170,63,192,0,16,2,9,2,40,128
1,4,7,2,5,8,3,6,9
*Access Matrix (40T, DS, DD, 350K)
36,4,15,1,174,63,128,0,16,2,9,2,40,192
1,4,7,2,5,8,3,6,9
*Acorn (80T, SS, SD, 392K)
20,4,15,1,195,127,192,0,32,3,10,1,80,0
0,1,4,5,8,9,2,3,6,7
*Adler Textriter Series III (40T, SS, DD, 160K)
32,3,7,0,159,31,128,0,10,0,16,1,40,128
1,4,7,10,13,16,3,6,9,12,15,2,5,8,11,14
*Altertext Diskreader (40T, SS, DD, 144K)
36,3,7,0,143,127,240,0,32,3,18,1,40,128
1,7,13,2,8,14,3,9,15,4,10,16,5,11,17,6,12,18
*Ampro Little Board (40T, SS, DD, 190K)
40,4,15,1,94,63,128,0,16,2,10,2,40,128
1,2,3,4,5,6,7,8,9,10
*Ampro Little Board (40T, DS, DD, 390K)
40,4,15,1,194,127,192,0,32,2,10,2,40,192
17,18,19,20,21,22,23,24,25,26
*AOS/VT Basic 4 S-10 (80T, DS, DD, 626K)
32,4,15,0,312,127,192,0,32,3,16,1,80,192
1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16
*Archives Model III (80T, DS, DD, 790K)
40,4,15,0,394,319,248,0,32,2,5,3,80,196
1,4,2,5,3
*ATR-8000 512 byte sector (40T, SS, DD, 190K)
40,3,7,0,189,63,192,0,16,2,10,2,40,128
1,2,3,4,5,6,7,8,9,10
*ATR-8000 1024 byte sector (40T, SS, DD, 190K)
40,3,7,0,189,63,192,0,16,2,5,3,40,128
1,2,3,4,5
*Aust. Comp. & Telecomm. (40T, SS, DD, 171K)
36,3,7,0,170,63,192,0,16,2,18,1,40,128
1,4,7,10,13,16,2,5,8,11,14,17,3,6,9,12,15,18
*AVATAR TC1 Terminal Converter (40T, SS, DD, 184K)
40,4,15,1,91,127,192,0,16,3,10,2,40,128
1,5,9,3,7,2,6,10,4,8
*AVATAR TC1 Terminal Converter (40T, DS, DD, 384K)
40,4,15,1,191,127,192,0,16,3,10,2,40,192
1,5,9,3,7,2,6,10,4,8
*BMC if800/20 (40T, DS, DD, 384K)
40,4,15,0,191,127,192,0,32,3,10,2,40,192
1,7,13,19,5,11,17,3,9,15
*California Computer Systems (40T, DS, DD, 332K)
36,4,15,1,165,63,128,0,16,6,18,1,40,192
1,5,9,13,17,3,7,11,15,2,6,10,14,18,4,8,12,16
*Cifer 2683 (40T, DS, DD, 384K)
40,4,15,1,191,127,192,0,32,3,10,2,40,192
1,3,5,7,9,2,4,6,8,10
*Compustar Model 30 (35T, DS, DD, 340K, *)
40,4,15,1,169,63,128,0,16,2,10,2,35,210
1,3,5,7,9,2,4,6,8,10
*Computer Operation NCHQ (40T, SS, SD, 82K)
18,3,7,0,81,63,192,0,16,3,18,0,40,0
1,3,5,7,9,11,13,15,17,2,4,6,8,10,12,14,16,18
*Cromemco Z-2 (40T, SS, SD, 82K)
18,3,7,0,81,31,128,0,8,3,18,0,40,0
1,6,11,16,3,8,13,18,5,10,15,2,7,12,17,4,9,14
*Cromemco Z-2 (40T, SS, DD, 190K)
40,3,7,0,189,31,128,0,8,2,10,2,40,128
1,5,9,3,7,2,6,10,4,8
*DEC Rainbow 100+ (80T, SS, DD, 390K)
40,4,15,1,194,127,192,0,32,2,10,2,80,128
1,3,5,7,9,2,4,6,8,10
*DEC RX50K (80T, SS, DD, 390K)
40,4,15,1,194,127,192,0,32,2,10,2,80,128
1,3,5,7,9,2,4,6,8,10
*DEC VT-180 (40T, SS, DD, 171K)
36,3,7,0,170,63,192,0,16,2,9,2,40,128
1,3,5,7,9,2,4,6,8
*Digital Research 8" CP/M Standard (77T, SS, SD, 243K)
26,3,7,0,242,63,192,0,16,2,26,0,77,0
1,7,13,19,25,5,11,17,23,3,9,15,21,2,8,14,20,26,6,12,18,24,4,10,16,22
*Digital Research 8" CP/M Standard (77T, DS, DD, 988K)
52,5,31,3,246,127,128,0,32,2,26,1,77,192
1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21,22,23,24,25,26
*Eagle (80T, SS, DD, 195K)
40,4,15,1,194,191,192,0,32,2,5,3,80,128
1,3,5,2,4
*Eagle (80T, DS, DD, 790K, *)
40,4,15,0,394,191,224,0,32,2,5,3,80,194
1,3,5,2,4
*ECB Bus (80T, DS, DD, 760K, *)
40,4,15,0,379,191,224,0,32,2,10,2,80,210
1,3,5,7,9,2,4,6,8,10
*Epson QX-10 (40T, DS, DD, 380K)
40,4,15,1,189,127,192,0,32,4,10,2,40,192
1,2,3,4,5,6,7,8,9,10
*Epson QX-10 MF (40T, DS, DD, 280K)
32,4,15,1,139,63,128,0,16,8,16,1,40,192
1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16
*Hewlett-Packard HP-125 (40T, DS, DD, 252K)
32,3,7,0,251,127,240,0,32,3,16,1,40,192
0,1,2,3,4,5,6,7,8,9,10,11,12,13,14,15
*Hewlett-Packard HP-87XM (35T, DS, DD, 244K)
32,3,7,0,243,127,240,0,32,3,16,1,35,192
0,1,2,3,4,5,6,7,8,9,10,11,12,13,14,15
*Holmes Engineering VID80 (40T, SS, DD, 195K)
40,3,7,0,194,63,240,0,16,1,10,2,40,128
0,1,2,3,4,5,6,7,8,9
*Hurricane Labs Inc. Compactor I & II (40T, SS, DD, 190K)
40,4,15,1,94,127,192,0,32,2,5,3,40,128
1,4,2,5,3
*IBM PC using CP/M 86 (40T, SS, DD, 156K)
32,3,7,0,155,63,192,0,16,1,8,2,40,128
1,2,3,4,5,6,7,8
*IBM PC using CP/M 86 (40T, DS, DD, 316K, *)
32,4,15,1,157,63,128,0,16,1,8,2,40,195
1,2,3,4,5,6,7,8
*Intertec Superbrain (35T, SS, DD, 164K)
40,4,15,1,81,63,128,0,16,2,10,2,35,144
1,3,5,7,9,2,4,6,8,10
*Intertec Superbrain (35T, DS, DD, 340K, *)
40,4,15,1,169,63,128,0,16,2,10,2,35,210
1,3,5,7,9,2,4,6,8,10
*Kaypro 2 (40T, SS, DD, 195K)
40,3,7,0,194,63,240,0,16,1,10,2,40,128
0,1,2,3,4,5,6,7,8,9
*Kaypro 2X, 4, & 10 (40T, DS, DD, 392K)
40,4,15,1,195,63,192,0,16,1,10,2,40,200
0,1,2,3,4,5,6,7,8,9
*Lifeboat TRS-80 Mod 1 (40T, SS, SD, 72K)
18,3,7,0,71,63,192,0,16,3,18,0,35,0
1,5,9,13,17,2,6,10,14,18,3,7,11,15,4,8,12,16
*LNW Research LNW80 (40T, SS, DD, 166K)
36,4,15,1,82,63,128,0,16,3,18,1,40,128
1,6,11,16,3,8,13,18,5,10,15,2,7,12,17,4,9,14
*Lobo MAX-80 (40T, SS, DD, 166K)
36,3,7,0,165,63,192,0,16,3,18,1,40,128
0,1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17
*Lobo MAX-80 (40T, DS, DD, 346K)
36,4,15,0,172,127,192,0,32,3,18,1,40,192
0,1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17
*Lobo MAX-80 CP/M 3.0 (40T, SS, DD, 185K)
40,3,7,0,184,63,192,0,16,3,10,2,40,128
0,1,2,3,4,5,6,7,8,9
*Lobo MAX-80 CP/M 3.0 (40T, DS, DD, 384K)
40,4,15,0,191,127,192,0,32,3,10,2,40,192
0,1,2,3,4,5,6,7,8,9
*Memory Merchant Shuffle Board (40T, SS, DD, 190K)
40,4,15,1,94,127,192,0,32,2,10,2,40,128
1,2,3,4,5,6,7,8,9,10
*Micro-Abacus (80T, DS, DD, 624K)
64,4,15,0,311,127,192,2,32,2,8,2,80,192
1,2,3,4,5,6,7,8
*Monroe OC 8820 (40T, DS, DD, 308K)
32,4,15,1,153,63,128,0,16,3,16,1,40,196
1,5,9,13,2,6,10,14,3,7,11,15,4,8,12,16
*Monroe OC 8820 (80T, SS, DD, 308K)
32,4,15,1,153,63,128,0,16,3,16,1,80,128
1,5,9,13,2,6,10,14,3,7,11,15,4,8,12,16
*Morrow Micro Decision (40T, SS, DD, 190K)
40,4,15,1,94,127,192,0,32,2,5,3,40,128
1,4,2,5,3
*Morrow Micro Decision MD3 (40T, DS, DD, 390K)
40,4,15,1,194,191,224,0,32,2,5,3,40,192
1,4,2,5,3
*NCR Decision Mate V (40T, DS, DD, 308K, *)
32,4,15,1,153,127,192,0,32,3,8,2,40,194
1,2,3,4,5,6,7,8
*NEC PC-8001A (40T, SS, DD, 148K)
32,3,7,0,147,63,192,0,16,2,16,1,40,128
1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16
*Octagon 8/16 CP/M-86 (40T, SS, DD, 156K)
32,4,15,1,77,63,128,0,16,1,8,2,40,128
1,2,3,4,5,6,7,8
*Octagon 8/16 CP/M-86 (40T, DS, DD, 316K)
32,4,15,1,157,63,128,0,16,1,8,2,40,192
1,2,3,4,5,6,7,8
*Omikron Mapper I, Model 1 & 3 (40T, SS, SD, 83K)
18,3,7,0,82,63,192,0,16,3,18,0,40,0
1,5,9,13,17,3,7,11,15,2,6,10,14,18,4,8,12,16
*Omikron Mapper II (40T, SS, DD, 134K)
28,3,7,0,133,63,192,0,16,2,28,0,40,128
1,6,11,16,21,26,3,8,13,18,23,28,5,10,15,20,25,2,7,12,17,22,27,4,9,14,19,24
*Omikron Mapper III (40T, SS, DD, 190K)
40,4,15,1,94,127,192,0,32,2,5,3,40,128
1,2,3,4,5
*Osborne 1 (40T, SS, SD, 90K)
20,4,15,1,45,63,128,0,16,3,10,1,40,0
1,3,5,7,9,2,4,6,8,10
*Osborne Executive (40T, SS, DD, 185K)
40,3,7,0,184,63,192,0,16,3,5,3,40,128
1,2,3,4,5
*Otrona 816A (40T, DS, DD, 364K, *)
40,4,15,1,181,127,192,0,32,3,10,2,40,194
1,2,3,4,5,6,7,8,9,10
*Otrona 816A (80T, DS, DD, 774K, *)
40,4,15,0,386,127,192,0,32,3,10,2,80,194
1,2,3,4,5,6,7,8,9,10
*Radio Shack TRS-80 Model 4 CP/M Plus (40T, SS, DD, 156K)
32,3,7,0,155,63,192,0,16,1,8,2,40,128
1,2,3,4,5,6,7,8
*Sanyo (40T, DS, DD, 312K)
32,4,15,1,155,63,128,0,16,2,16,1,40,192
1,4,7,10,13,16,3,6,9,12,15,2,5,8,11,14
*Sanyo MBC-1200/1250 (80T, DS, DD, 624K)
32,5,31,3,155,127,128,0,32,4,16,1,80,192
1,4,7,10,13,16,3,6,9,12,15,2,5,8,11,14
*Sperry UTS-30 (80T, DS, DD, 710K)
36,4,15,0,354,383,252,0,32,2,9,2,80,192
1,2,3,4,5,6,7,8,9
*Tecron TEF System 10 (80T, DS, DD, 790K)
40,4,15,0,394,319,248,0,32,2,10,2,80,192
1,4,7,10,3,6,9,2,5,8
*Tektronics 4170 CP/M 86 (40T, DS, DD, 316K, *)
32,4,15,1,157,63,128,0,16,1,8,2,40,195
1,2,3,4,5,6,7,8
*Teletek Systemaster (80T, SS, SD, 72K)
18,3,7,0,71,127,240,0,32,3,18,0,80,0
1,5,9,13,17,3,7,11,15,2,6,10,14,18,4,8,12,16
*Teletek Systemaster (40T, SS, DD, 144K)
36,3,7,0,143,127,240,0,32,3,18,1,40,128
1,7,13,2,8,14,3,9,15,4,10,16,5,11,17,6,12,18
*Televideo 802 (40T, DS, DD, 342K)
36,4,15,0,170,63,128,0,16,4,18,1,40,192
1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18
*Toshiba T-100 (40T, DS, DD, 256K)
32,3,7,0,255,63,192,0,16,6,16,1,40,192
1,5,9,13,2,6,10,14,3,7,11,15,4,8,12,16
*Video Genie III (80T, DS, DD, 692K)
36,5,31,3,172,127,128,0,32,6,18,1,80,200
0,1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17
*Visual 1050 (80T, SS, DD, 390K)
40,4,15,1,194,127,192,0,32,2,10,2,80,128
1,2,3,4,5,6,7,8,9,10
*Xerox 820-1 (40T, SS, SD, 82K)
18,3,7,0,81,31,128,0,8,3,18,0,40,0
1,6,11,16,3,8,13,18,5,10,15,2,7,12,17,4,9,14
*Xerox 820-2 (40T, SS, DD, 157K)
34,3,7,0,156,63,192,0,16,3,17,1,40,128
1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17
*XOR S100-4 (40T, SS, DD, 185K)
40,3,7,0,184,127,240,0,32,3,10,2,40,128
1,6,2,7,3,8,4,9,5,10
*Zenith H89 (40T, SS, SD, 94K)
20,3,7,0,93,63,192,0,16,3,10,1,40,0
1,2,3,4,5,6,7,8,9,10
*Zenith H89/H90 (40T, SS, DD, 152K)
32,3,7,0,151,127,240,0,32,2,16,1,40,128
1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16
*Zenith H90 (80T, DS, DD, 632K)
32,4,15,0,315,255,240,0,32,2,16,1,80,192
1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16
*Zenith Z100 (40T, SS, DD, 152K)
32,3,7,0,151,127,240,0,32,2,8,2,40,128
1,2,3,4,5,6,7,8
*Zenith Z100 (40T, DS, DD, 312K)
32,4,15,1,155,255,240,0,32,2,8,2,40,192
1,2,3,4,5,6,7,8
*Zorba GC200 (40T, DS, DD, 390K)
40,4,15,1,194,63,128,0,16,2,10,2,40,200
1,2,3,4,5,6,7,8,9,10
*Montezuma Micro CP/M v 1.26 & 1.30 (40T, SS, DD, 170K)
36,4,15,1,84,127,192,0,32,2,18,1,40,128
1,5,9,13,17,3,7,11,15,2,6,10,14,18,4,8,12,16
*Montezuma Micro CP/M v 1.26 & 1.30 (40T, DS, DD, 350K, *)
36,4,15,1,174,127,192,0,32,2,18,1,40,194
1,5,9,13,17,3,7,11,15,2,6,10,14,18,4,8,12,16
*Montezuma Micro CP/M v 1.32 (40T/256S, DS, DD, 350K, *)
36,4,15,1,174,127,192,0,32,2,18,1,40,194
1,3,5,7,9,11,13,15,17,2,4,6,8,10,12,14,16,18
*Montezuma Micro CP/M v 1.42 & 1.44 (40T, DS, DD, 342K)
36,4,15,1,170,127,192,0,32,4,18,1,40,192
1,3,5,7,9,11,13,15,17,2,4,6,8,10,12,14,16,18

Larry

 

[oktology]

Do you have a Model 4P with 80 track disks installed?

Not currently, but among my Tandon TM-50s (40 track drives) I only have one DS drive that works and one SS drive that's a bit cantankerous, so I'm looking at the options to replace drives and HD drives seem to be a lot easier to find at non-exorbitant prices (I'm not paying $100 for a used floppy drive, that's insane, they aren't rare) than DD ones.

The Model 4 running Montezuma Micro Ver 2.31 CONFIG command

This sounds like CP/M? I'll be running TRS-/LS-DOS on this machine.

I notice some of the formats in that list call for 80 tracks and single density; I was under the impression that number of tracks was what determined density.

 

[Eudimorphodon]

so I'm looking at the options to replace drives and HD drives seem to be a lot easier to find at non-exorbitant prices

The most common high density 5.25” drives, IE, the ones used in the PC/AT and clones, spin at 360 RPM instead of the 300 RPM of the “quad density(* more on this below)” 80 track drives used on TRS-80s and the like, so trying to use one of them opens up a *big* kettle of fish. Basically you’ll have to treat it like an 8” floppy drive (which a few DOSes support, but it’s getting pretty far out in the weeds) and I don’t think you’ll be able to read disks written at the standard RPM with the Tandy controller.

(* A *few* of those drives had a jumper to automatically spin at 300 RPM instead of 360 when using double density data rates instead of HD, one of those might work, but since the PC didn’t need that you’re going to have fun finding one.)

I notice some of the formats in that list call for 80 tracks and single density; I was under the impression that number of tracks was what determined density.

Nope. “Density” in this context refers to the effective data rate of the controller and whether it’s using FM or MFM encoding. TL;DR, “double density” MFM encoding fits about twice as much data per track as FM “single density” encoding. ”High density” like on AT 5.25” drives and HD 3.5” drives refers to the clock speed of the data spitting out of the disk controller; it’s twice as fast, and usually MFM encoded... and I don’t think the stock 4P controller can run at this data rate, so using one of these drives at full capacity is right out from the start.

The confusing exception, and maybe the source of your impression, is sometimes the people selling 80 track double-density capable drives called them “quad density” to emphasize that with the right controller you can hold 4 times as much data as a “standard” single-density 40 track disk. It’s just marketing, these drives can be formatted either single or double density like a “normal” drive, it just has narrower tracks and more of them.

Anyway, if you want a “quad density” drive you’re going to have a really fun time finding one. If you see someone dumping a dead Tandy 2000 it’d work as a source of drives, otherwise… yeah, they’re rare.

Maybe you should consider 3.5” drives instead. You can treat HD 3.5” drives as 80 track double density no problem, they spin at 300RPM so the wrong RPM quirk goes away. You’re just stuck with having to track down double density (“720k”) media.

 

[oktology]

Dang, thanks for all the info, Eudimorphodon.

It sounds like the issue with quad density isn’t the OS support so much as finding a drive that does 80 tracks AND two sides.