--- morrison(a)t-iii.com wrote: There has been extensive discussion on this topic on the comp.os.cpm newsgroup in the past several years. Here's some articles that detail which PC floppy disk controllers are capable of reading/writing single- density disks: Ken Ganshirt <ken.ganshirt(a)sk.sympatico.ca> wrote in article <36899CB0.19AD9093(a)sk.sympatico.ca>ca>... Ken, I recently did a study to find out what will and what won't do single density. Here are my findings so far: Will support single density / FM: NS PC87306 Super I/O SMC FDC37C65 SMC FDC37C78 Most SMC Super I/O chips Will NOT support single density / FM: NS 8473 NS PC87332* Super I/O NS PC97307* Super I/O WD FDC37C65 Most (if not all) Intel parts Any Winbond part Any UMC part Reportedly will do single density / FM but NOT verified: NS 8477 Intel 82077AA Goldstar Super I/O The NS PC87306 is found in a lot of Dell and Compaq machines from the 486-50Mhz models to the Pentium-90 models. Most Super Micro Pentium motherboards using the PCI HX chipset also used that super I/O. *NOTE: It is important to verify the part number on the chip itself. Many of these newer NS parts will identify themselves to software as PC87306, but do NOT support single density. Best regards, Amardeep Amardeep S. Chana (asc1000(a)ibm.net) wrote: : Ken Ganshirt <ken.ganshirt(a)sk.sympatico.ca> wrote in article : <36899CB0.19AD9093(a)sk.sympatico.ca>ca>... : > : > I must have a pretty decent floppy controller, because I can even read : > my original SS/SD Os-1 floppies, even though 22Disk warns that it might : > not work for that format. (For the technically curious, this is on a : > Dell 486/50 running Win 95 and the floppy drive is one of those deals : > that has both a 3.5 and 5.25 in a single half-height drive. It's the : > only system I have left with a 5.25" floppy drive.) : > : Ken, : I recently did a study to find out what will and what won't do single : density. Here are my findings so far: Amardeep, I fear that I must question your study. I believe that you are ascribing to some of the chips the shortcomings of the FDC manufacturer. For example, both the NS 8473 and the WD 37C65 will most assuredly support FM. I have DTK FDC cards with the 8473 and read Osborne 1 disks with them just prior to writing this. Likewise, I have the WD 37C65 in the WD FOX card and it will also read/write FM. On that basis, I must have reservations about some of your other determinations. - don : Will support single density / FM: : NS PC87306 Super I/O : SMC FDC37C65 : SMC FDC37C78 : Most SMC Super I/O chips : Will NOT support single density / FM: : NS 8473 : NS PC87332* Super I/O : NS PC97307* Super I/O : WD FDC37C65 : Most (if not all) Intel parts : Any Winbond part : Any UMC part : Reportedly will do single density / FM but NOT verified: : NS 8477 : Intel 82077AA : Goldstar Super I/O : The NS PC87306 is found in a lot of Dell and Compaq machines from the : 486-50Mhz models to the Pentium-90 models. Most Super Micro Pentium : motherboards using the PCI HX chipset also used that super I/O. : *NOTE: It is important to verify the part number on the chip itself. Many : of these newer NS parts will identify themselves to software as PC87306, : but do NOT support single density. : Best regards, : Amardeep Don Maslin <donm(a)cts.com> wrote in article <915064276.933215(a)optional.cts.com>om>... [snip] Hi Don, I understand your reservations and can address every issue. I did not go into enough detail in the first posting to fully support my assertions. The above parts are completely stand alone with on board filters, write precomp generators, and data separators. They should work with FM in any board implementation, unless something specific is done to prevent it (not likely). This is per the National and SMSC (new name for SMC semiconductor) data sheets. I have tested the NS PC87306 and SMC FDC37C65 using Jeff Vavasour's Model 4 emulator and Tim Mann's xtrs 2.8 under Linux. They both read and write FM with no problems. The 1988 data sheet for the NS 8473 states on page 8-32, "While the controller and data separator support both FM and MFM encoding, the filter switch circuitry only supports the IBM standard MFM data rates. To provide both FM and MFM filters external logic may be necessary." Every 8473 board I have tried failed to write FM. However, it may be possible to read FM on some boards if the external filters have a wide enough Q. The NS PC87332 & NS PC97307 are standalone and by design do not support FM (verified on the National data sheets). The only information I have on the WD FDC37C65 is the Always IN2000 card I have with that chip cannot read or write FM. I suspect it is also dependent on implementation. I have new information on Intel... Intel 8272 is a NEC 765 clone and therefore dependent on implementation . Intel 82077AA and 82077SL - data sheet clearly states these parts suppo rt FM. Thanks to Pete Cervasio for testing and reporting that the 82077 does indeed read and write FM. Intel 82078 - data sheet clearly states these parts will NOT support FM . I haven't yet investigated the new Intel Super I/O chip which is replacing the 82078. The Winbond and UMC chips have never worked on any adapter or motherboard I've ever encountered them on. No idea if its the chip or the implementation. The NS 8477 data sheet indicates that it does support FM (it is functionally and pin for pin compatible with the Intel 82077). The Goldstar Super I/O was reported to work with FM in a newsgroup posting I read once but have never been able to confirm it. Hope that clarifies things :) Amardeep