Dumping a mixed FM/MFM floppy

[jltursan]

There're several mixed FM/MFM floppy formats out there: Olivetti M20, Toshiba Pasopia, Spectravideo SVI-3x8 and many others. Usually there's only one FM track (boot) and the rest are MFM tracks; but this fact made these disks a PITA to work with.

Anyone knows which hardware (I mean FDC controllers) + software combination works good enough to be able to read and write them?

 

[fritzeflink]

I use:

adaptec 1522a + IMD or teledisk 2.16

catweasel MK1 + cw2dmk from Tim Man http://www.tim-mann.org/catweasel.html

the systems are PC with ISA/PCI board P1/P2 - 100/400MHz or 486/33 isa or 386/isa board.

It's good to have 40 and 80 track drives for writing, reading will mostly be good with a 1,2mb diskdrive

Some interesting info is at http://www.classiccmp.org/dunfield/img/index.htm

-> http://www.classiccmp.org/dunfield/img54306/pcfdc.txt

 

[ldkraemer]

jltursan,
If you want a 100% Copy of the Floppy as in preservation, there is:

HARDWARE:
1. Kyroflux
2. Supercard Pro
3. Discferret
4. CatWeasel

SOFTWARE:
4. Imagedisk (.IMD)
5. Teledisk (TD0)
6. SAMDisk

But, if you have a system/data disk, and just want to read and write files to the Floppy's (or images of Floppy's) there is:

DOS ONLY:
1. 22DISK

Windows, Linux, MAC:
2. cpmtools (without libdsk)
2. cpmtools (with libdsk)

I'm using an old Win box with an ISA Slot that has a Adaptec AHA-1522 SCSI Controller which uses the Floppy ONLY port.
It passes the FDC test with Imagedisk.

What exactly are you wanting to do? Do you have a couple sample images that we can download?


Larry

 

[lowen]

There're several mixed FM/MFM floppy formats out there...

What's really fun are the TRS-80 Model I/III dual-boot disks where there is mixed-density FM and MFM in the same track.

Anyone knows which hardware (I mean FDC controllers) + software combination works good enough to be able to read and write them?

Catweasel can read and write these formats (even the TRS-80 Model I/III dual-boot ones) as long as an image file format that recognizes mixed-density, such as DMK, is used.

Since you didn't specify PC-only (although that is probably what you meant), a TRS-80 Model III or 4, especially the non-gate-array Model 4, can read and write these mixed-density formats just fine, but only at the 'low-density' data rate. For PCs with regular FDCs the choices are more limited, and to the best of my knowledge a 765-style FDC can't do the mixed-density within a single track format prior to the write. You have to have special creator programs even on the TRS-80's to make copies of these disks since the techniques used to get a mixed-density track are specific to the particular disk (how many sectors FM versus MFM; many if not most of these dual-boot disks have a single block of one to a few MFM sectors for the Model III boot with the rest of the sectors on track 0 being FM and all other tracks being FM as well).

EDIT: The FM/MFM mixed in one track format is possible on the TRS-80's because the WD1793 controller has two specific features in its feature set: variable post-index gap, and a Force Interrupt command. These two features together make it possible to write a track in one format with a long post-index gap, then overlay a write track in the other format, then issue a Force Interrupt before the write track gets to the end of the first format's post-index gap. It's partly because the write track on the WD179x controllers requires the programmer to write out pretty much every byte of a whole track that this works at all.

I'm not sure how mature the write support of the Kryoflux is; I have a Kryoflux but haven't had opportunity to put it to much use as yet; my two Catweasels (one Mk3 and one Mk4) are my workhorses when I have needed to read and write odd formats in the past. I use the cw2dmk tool available from Tim Mann's website.

FM support in typical PC 765-style FDCs is very spotty; Dunfield's site and ImageDisk utilities can help you find out if your specific controller has the support.

 

[SomeGuy]

Typically mixed FM/MFM disks, as described, are archived with ImageDisk on an IBM PC compatible with a real floppy disk controller. But the catch is not all IBM PC floppy controllers support FM encoding. If you can find an Adaptec SCSI controller with a National Semiconductor FDC chip.

The "modern" solution would be a Kryoflux. It reads and duplicates images at the flux-transition level where encoding is irrelevant. The catch there is if you want to convert the flux stream image to an Imagedisk, DMK, or other emulator format. The Kryoflux provided software is not so good with that. However the go-to answer for most conversations is the HxC software tools.

There is a review of current disk archival tools here that might help: https://winworldpc.com/winboards/viewtopic.php?f=1&t=7877

 

[Dwight Elvey]

I believe Dave Dunfield has a test program to test for FM read/write with.
Dwight

 

[glitch]

I believe Dave Dunfield has a test program to test for FM read/write with.
Dwight

Yes, it comes with ImageDisk. I use an Adaptec AHA-1522/1542 controller in my utility PC, someone else already mentioned it. Make sure you get one with the onboard floppy controller. Some of the later (C and higher, IIRC) revisions switched to a different controller that doesn't do FM. I've also found that the Adaptec controllers will talk to a number of old drives, especially tape drives, that my AHA-2940 doesn't like.

 

[Chuck(G)]

Look at the floppy controller chip itself. There are number that do just fine with FM. National 8477, 8473, 8474; some of the SMSC "Superio" (but not all); the original Intel 82077, but not the 82077AA, etc. WD37C65 is another good one.

 

[jltursan]

I have a real mess here, I've been testing different Adaptec FDC controllers and I'm still not sure about what's my mileage
The cards, if I'm not wrong, are the AHA-1520/22, AHA-1522A and AHA-1542CF, always paired with a 5.25" drive, a TEAC FS-55GFR-541-U, suposedly a very competent drive. The mainboard also seems to have a good chipset, it's an Asus P5A-B; but I suposse the Adaptec cards are a bit better when it comes to supported formats.

Right now I'm mainly using SamDisk and due this tool I've favored the AHA-1542CF as it seems to work "fast", I'm saying this because when I use 152x cards, the track access is extremely slow (say about 4-5 seconds per track), although it seems to work. With the 1542 I can write FM+MFM images; but not reading them.

I can also try with more drives (they must be 1.2MB ones); but TEAC are probably the best units out there so I want to stick with the 55GFR.

I'll try to get some figures using "testfdc" and mixing cards, I'm really intrigued about the differences between the Adaptec cards...

 

[SomeGuy]

You can use TESTFDC included with ImageDisk to test the full capabilities of the FDC chips.

I would expect the FDC on all of these Adaptec cards to perform about the same.

Sometimes poorly coded BIOS can affect performance, but in that case tools that bypass BIOS would be unaffected. ISA speed issues could also be a factor, as well as default step rate.