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Thread: Recent motherboard FDC and "legacy" tests

  1. #1
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    Default Recent motherboard FDC and "legacy" tests

    I decided to test the "legacy" compatiblity of several recent motherboards I acquired. The results were rather interesting.

    All of the boards tested could successfully emulate PS/2 hardware compatiblity with a USB keyboard. However, I could not get USB mice to emulate PS/2 hardware compatiblity. (It's probably not supposed to, but they don't tell you that!)

    I also tested a USB floppy drive in combination with the real floppy drive to determine BIOS drive behavior. Each mapped the USB floppy as B: when a real floppy drive was present, unless it booted from the USB floppy. In that case the USB floppy became A: and the real drive became B:

    In testing, I also noticed that BIOS does not support low-level formatting disks in USB Floppy drives. All format calls do nothing and return "successful". It is also worth noting here that most USB floppies, including the one I tested with, do not support 720k disks or formats that deviate from the common 1.44mb format.

    Each of these boards only support ONE floppy disk drive. Attaching a second drive in the standard way will do nothing. It wouldn't be too hard to wire up a manual switch to switch between drives, but the mind boggles as to why they would leave that out.

    I also tested compatiblity with a copy (sorry, not an original) of IBM PC-DOS 1.00 on both 5.25" and low density 3.5" disks, and booting an original copy-protected Pinball Construction Set 5.25" disk. Several of the AMI bioses require the "55AA" ID at the end of the boot sector, which DOS 1.00 and early booters lack. Booting Pinball Construction Set or similar also tests the ability of the system to handle floppy disk copy protection.

    My primary goal was to test floppy disk compatiblity, as such I did not extensively test COM or LPT ports. All COM and LPT ports appeared as standard ports to DOS diagnostics.

    For formatting tests, I used both the DOS formatter and NFORMAT.

    Gigabyte GA-870A-UD3
    --------------------
    Bios: Award
    Supports a SINGLE 2.88mb, 1.44mb, 1.2mb, 720kb, or 360k floppy drive with "Mode 3" option.
    Other: SINGLE PS/2 port, one COM header, LPT header, IDE.
    Note: The the single PS/2 port can be used with either a keyboard or a mouse, but is not wired for use with a splitter.
    Setup: Must specify FDD type in the BIOS.

    TestFDC:
    250K SD - Fail
    250K DD - Pass
    250K DD/128 - Fail
    500K SD - Fail
    500K DD - Pass
    500K DD/128 - Fail

    General Format/Read/Write tests:
    1.44mb (1.44mb and 720k media) - OK
    720k - OK
    1.2mb (1.2mb and 360k media) - OK
    360k - OK

    Formats/Reads/Writes 1.7mb disks in 1.44mb drive (21 sectors per track) - OK
    Note: Requires FDREAD or BIOSPTCH under DOS 6.22 or earlier.

    Boots DOS 6.22: Yes
    DOS 6.22 Backup test: Passed
    Boots unmodified DOS 1.00 (on 5.25" and 3.5"): Yes
    Boots Pinball Construction Set 5.25" disk: Yes.


    ASRock 880GM-LE FX
    ------------------
    Bios: AMI
    Supports a SINGLE 2.88mb, 1.44mb, 1.2mb, 720kb, or 360k floppy drive.
    Other: PS/2 mouse port, PS/2 keyboard port, one COM header, LPT header, IDE.
    Setup: Must specify FDD type in the BIOS.

    TestFDC:
    250K SD - Pass!!
    250K DD - Pass
    250K DD/128 - Fail
    500K SD - Pass
    500K DD - Pass
    500K DD/128 - Fail

    General Format/Read/Write tests:
    1.44mb (1.44mb and 720k media) - OK
    720k - OK
    1.2mb (1.2mb and 360k media) - OK
    360k - OK

    Formats/Reads/Writes 1.7mb disks in 1.44mb drive (21 sectors per track) - OK
    Note: Requires FDREAD or BIOSPTCH under DOS 6.22 or earlier.

    Boots DOS 6.22: Yes
    DOS 6.22 Backup test: Fails (Seems to fail writing the second disk)
    Boots unmodified DOS 1.00 (on 5.25" and 3.5"): No - This bios requires the "55AA" boot ID on the boot sector.
    Boots modified DOS 1.00 (on 5.25" and 3.5"): Yes
    Boots Pinball Construction Set 5.25" disk: No.

    BIOSTAR A770E3
    ------------------
    Bios: AMI
    Supports a SINGLE 2.88mb, 1.44mb, 1.2mb, 720kb, or 360k floppy drive.
    Other: PS/2 mouse port, PS/2 keyboard port, one COM port, LPT header, IDE.

    TestFDC:
    250K SD - Fail
    250K DD - Pass
    250K DD/128 - Fail (And hangs!)
    500K SD - Fail
    500K DD - Pass
    500K DD/128 - Fail

    General Format/Read/Write tests:
    1.44mb (1.44mb and 720k media) - OK
    720k - OK
    1.2mb (1.2mb and 360k media) - OK
    360k - OK

    Formats/Reads/Writes 1.7mb disks in 1.44mb drive (21 sectors per track) - OK
    Note: Requires FDREAD or BIOSPTCH under DOS 6.22 or earlier.
    Note: Behaves strangely if not power cycled after changing the bios drive type.

    Boots DOS 6.22: Yes
    DOS 6.22 Backup test: Fails (Seems to fail writing the second disk)
    Boots unmodified DOS 1.00 (on 5.25" and 3.5"): No - This bios requires the "55AA" boot ID on the boot sector.
    Boots modified DOS 1.00 (on 5.25" and 3.5"): Yes
    Boots Pinball Construction Set 5.25" disk: No.

    ASRock 990FX Extreme 4
    ----------------------
    Bios: AMI UEFI
    Supports a SINGLE 1.44mb floppy drive.
    Other: PS/2 mouse port, PS/2 keyboard port, one COM header, IDE.
    Note: There is no way to specify any drive type other than 1.44mb! (Or at least I can't find one)
    Note: Lacks an LPT port.
    Note: A vesa video mode test failed, even though this was the same video card used on the Gigabyte board tests.

    TestFDC:
    250K SD - Pass!!
    250K DD - Pass
    250K DD/128 - Fail
    500K SD - Pass
    500K DD - Pass
    500K DD/128 - Fail

    General Format/Read/Write tests:
    1.44mb (1.44mb and 720k media) - OK
    720k - Fail (no support!?)
    1.2mb (1.2mb and 360k media) - Fail (no support!?)
    360k - Fail (No Support!?)

    Formats/Reads/Writes 1.7mb disks in 1.44mb drive (21 sectors per track) - OK
    Note: Requires FDREAD or BIOSPTCH under DOS 6.22 or earlier.

    Boots DOS 6.22: Yes
    DOS 6.22 Backup test: Pass
    Boots unmodified DOS 1.00 (on 3.5"): Yes

    Note: You can connect a 720k, 1.2mb, or 360k drive with varying levels of success but OSes will assume it is a 1.4mb drive. I did get it to boot DOS 1.00/PBCS from 360k but the BIOS forces a seek test at boot that the 360k drive doesn't really like. Some tools like ImageDisk and NFORMAT can be configured to ignore the BIOS settings, but standard tools may fail. Under DOS 6.22 you may be able to use the DRIVEPARM command to work around the lack of bios support. (But really, WTF?)
    I also verified the FDC chip can do 300K bps, but forgot to run TestFDC on the 1.2mb drive tests.

    On a side note, their graphical BIOS setup is ugly, and they advertise it as if it were a brand new invention.
    Also, interestingly, even though this is a UEFI BIOS there was no mention of "secure boot" in the version shipped with the board. An update adds secure boot but it is disabled by default. - Somehow I don't think IBM PC-DOS 1.00 is digitally signed

    Conclusion
    -----------
    Each of these boards has its pros and cons with regard to legacy support. Over all, the Gigabyte board and the Award BIOS feels much more "solid" than the others, but the lack of a second PS/2 port is a drawback.

    I was greatly surprised that that the 990FX and the 880GM-LE FX could read/write single density modes. Note that it is possible this ability may vary from board to board if they use different IO chips.

    If there is some trick to set the drive type in the 990FX, that would be a winner simply for being the latest model with an FDC that I could find. (And a bonus for supporting SD!). It lacks an LPT, but has plenty of PCI/PCIe expansion for a Serial/Parallel card.

  2. #2
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    Just for yucks, on the 990, have you tried using one of the CMOS editors and changing the drive type manually? I don't know if it would work, but it's worth a shot. Actually, most of the newer chipsets using "SuperIO" chips are pretty successful in their support of FM floppies. FWIW, the original NEC 765 chip doesn't support DD 128 byte sectors, so no surprise there. A few NSC chips do, which is why I keep a couple of spare controllers around.

    USB support is no surprise. The idea is to get you booted, nothing more. On the other hand, have you tried any real-mode USB drivers for the thing? That might work better, although you'll still be limited to 512/18/2/80 and perhaps 512/9/2/80 formats. Forget about formatting XDF format.

    Too bad there's no parallel port support; it would at least allow you to use a couple of "Backpack" drives.

    Bottom line--I think you'll agree with me--that there's no substitute for a real "tweener". Fortunately, they still can be had for peanuts on the scrap market. If you get one such (say, a P3 unit) with ISA slots, i440BX is about the latest you can get full ISA (8 bit DMA) support for.

  3. #3
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    What CMOS editor would you recommend?

    I did actually try a couple of old AT CMOS setup tools, but after rebooting the BIOS says the CMOS is corrupted and sets everything back. Googling around, the only editors I see are really just meant for backing up and restoring. I'd need something that tells the AMI BIOS that the data is valid (if that is even possible).

    It does "feel" like the ability to recognize these other drive types might still be in there somewhere. The thing that really gets me is that they don't say anything about being limited to 1.44mb in the documentation!!

    And yea, a real "tweener" really needs support for two floppy drives (or more! ), preferably also ISA slots, and Win9x support.

    But I think it is nice to have some of these these abilities in something that is new.

  4. #4
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    Well, give ImageDisk a try on some sample "not 1.44M" floppies. IMD doesn't care what the BIOS says about the drive--it's a direct interface. At least you can determine if the capability exists in the chipset. Nowadays, I wouldn't be surprised if the BIOS has been stripped to bones of floppy support.

  5. #5
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    Yes, I tried ImageDisk, that is how I determined it could do 300k bps. It was able to read from a 360k disk in a 1.2mb drive on the 990FX even though DOS/BIOS was barfing on it.

    That is why I was testing them, to see how far off the "modern" drive support is. If I had more time I am sure I could find all kinds of smaller compatiblity issues and missing bits. But then again, there were some machines that even back in the day had buggy support. I remember some 386 or 486 machines (HP?) that confused the heck out of NFORMAT.

  6. #6
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    Incidentally, just for the heck of it I e-mailed ASUS tech support about setting the floppy type in the bios on the 990fx. Unsurprisingly I got back a reply in broken English saying they don't support that.
    And DRIVPARM doesn't quite work. As I recall now that is really meant for BIOSes with no functionality for reporting what kind of drive it is. In this case the functionality is there but it is crippled to always say one thing. DOS Format defaults to the right format type but fails saying the parameters are not supported by the drive.
    Also NFORMAT can activate 300k bps and double stepping for a 360k in 1.2mb with the right detailed manual settings, even though that purely uses BIOS calls.

  7. #7
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    Are you doing your testing strictly in DOS mode? If so, a installable device driver may solve the issue by simply providing its own BIOS/driver interface.

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