Image Map Image Map
Results 1 to 10 of 10

Thread: 5.25 Floppy disk compatibility questions.

  1. #1

    Default 5.25 Floppy disk compatibility questions.

    I will soon need to create 5.25" 40 tpi 360kB floppys to use in the drives I'm setting up for a Sol-20 computer. The only computer I have though with a working 5.25 floppy drive currently has 1.2MB 96 tpi drive.

    I understand some of the issues with incompatibilty; for example trying to record a 96tpi track on a previously recorded 48tpi disk, where it doesn't fully erase the wider 40 tpi tracks and a noisy recording results.

    There are two basic questions I have:

    1) If a 96tpi 1.2MB type drive attempts to read a 320Kb 48 tpi disk, how is this possible (is it) ? If the drive makes smaller steps between tracks(cylinders) won't it end up reading essentially the same track twice ?

    2) Is it possible to force a 1.2MB 96 tpi drive, by selecting with jumpers on the card that is controlling it, to 360kB, so that it makes a 40 cylinder recording with equal pairs of tracks resembling a wider single track, (Say on a previously unformatted floppy), with tracks that would be expected to probably read normally in an older 48 tpi /40 cylinder floppy drive ? OR will the controller card not be able to force the 1.2MB drive to do that ?

  2. #2

    Default

    Quote Originally Posted by Hugo Holden View Post
    I will soon need to create 5.25" 40 tpi 360kB floppys....

    1) If a 96tpi 1.2MB type drive attempts to read a 320Kb 48 tpi disk,...
    Is actually this what you meant to say or is there a typo lurking in there?
    ☀☀☀ Visit Take Another Step for both computer and non-computer related discussions. ☀☀☀

    If you're looking for DS/DD or DS/HD 3" or 5" floppy disks, PM me. I've got some new, used, and factory over-labeled disks for sale.

    There is a crack in everything. That's how the light gets in. -- Leonard Cohen

  3. #3
    Join Date
    Jan 2007
    Location
    Pacific Northwest, USA
    Posts
    28,212
    Blog Entries
    20

    Default

    1) The technique is to "double step" the 96 tpi drive to match the spacing of the 48 tpi one. If you write to a previously-formatted genuine 48 tpi disk with a 96 tpi drive, it will always be okay for reading by a 96 tpi, but hit-or-miss for reading on a 48 tpi unit. Success depends a lot on the technology used in both drives.

    2) No, the speed reproducibility on even a direct-drive spindle is not adequate. Consider, for example, that if you're off by so much as half a bit cell time, you've got problems. A 1.2MB drive spins at 360 RPM or 6 rev/second or 167 msec per revolution. Now consider that the bit cell time on a DD floppy is 2 microseconds. See the problem? You're asking for a speed that's in agreement to 2/167000 or .001 percent. Consider that formatting usually begins at the edge of the INDEX pulse, which is an optical sensor responding to a hole in the floppy. The tolerance there to getting INDEX in exactly the right spot is simply not achievable to the needed tolerance--and that's not accounting for things such as frictional losses between the heads and media or the ISV (instantaneous speed variation) of the drive motor or even "bit crowding" effects.

    The best thing is to degauss the floppy, so that there's no coherent background signal and format and write with the 96 tpi drive. A 48 tpi drive should read the result fine. If you don't have something like a videotape eraser, you can make an ersatz floppy degausser from a couple of ring magnets from an old microwave oven magnetron. The magnets are placed with like poles facing and separated by a few mm, all held in a non-magnetic holder (such as wood). Seems to work well--you just pass your floppy through the gap between the magnets.

  4. #4

    Default

    Stone,
    can you point me to where I went wrong with the question ?

  5. #5

    Default

    Quote Originally Posted by Chuck(G) View Post
    The best thing is to degauss the floppy, so that there's no coherent background signal and format and write with the 96 tpi drive. A 48 tpi drive should read the result fine. If you don't have something like a videotape eraser, you can make an ersatz floppy degausser from a couple of ring magnets from an old microwave oven magnetron. The magnets are placed with like poles facing and separated by a few mm, all held in a non-magnetic holder (such as wood). Seems to work well--you just pass your floppy through the gap between the magnets.
    Chuck, I have a TV degaussing wand that should do it.
    That is great, it means I can get the CP/M disk images into my 5155 initially (via its 3.5" drive) and then make the 5.25 96tpi floppys in its 1.2MB drive and then they should work in the 48tpi drive with the sol-20. I wasn't sure if that process would work.

  6. #6

    Default

    Hugo,

    If you are attempting to make disks for the Sol-20 running the North Star floppy controller you purchased, then you cannot write the disks with a soft sector controller - you must write them using the Sol-20 and the North Star Controller. The virtual sector generator (VSG) you’re gettting does NOT let a hard sector controller read a disk written by a soft sector controller. It simply lets you use soft sector MEDIA with a hard sector controller.

    The image transfer program (PC2FLOP) that is in the directory tree with the Sol-20 North Star disk images runs on the Sol-20 and writes a disk as the image is transferred into the Sol through a serial port. PC2FLOP can run on a “cold” machine without an OS, so a pre-existing boot disk is NOT required.

    Mike

  7. #7

    Default

    Mike,

    Thanks, I understand now about the hard sector controller and I didn't know I could run PC2FLOP on a cold machine, I was thinking I'd have to make a a boot OS disk.

  8. #8

    Default

    Mike,

    I have been reading the instructions:

    http://deramp.com/downloads/processo...fer/ReadMe.pdf

    The remark under the first option 1) "Send the program PC2FLOP.COM through the Sol-20 serial port.."

    What would be a suitable program on a "modern PC" to do that ? Would Procomm be ok ?

    I'm also confused about possibility number 3) using a Prom. Is this suggesting programming a Prom with the Intel hex file of PC2FLOP in a prom burner and putting that prom in the Sol-20 to transfer the program that way ?

    Would it be easier initially to have PC2Flop on a disk (in my case) to get started at least, can I buy a disk from you ?

  9. #9

    Default

    Hugo,

    The three options listed in the readme file are techniques for getting the PC2FLOP program loaded into memory in a cold machine if you don't have a bootable disk. Options 1 and 2 will work fine for you and don't require adding a PROM. The PROM option mentioned is simply a PROM with an Intel hex file loader so that you could load the .hex version of PC2FLOP into RAM.

    I'd recommend using TeraTerm on a modern PC (http://altairclone.com/downloads/teraterm477.zip). If you have an older MS-DOS PC, then Procomm is fine. You'll use simple 8-bit file send (i.e., not XMODEM, etc.) to send PC2FLOP.COM or PC2FLOP.ENT to the SOL as detailed in option 1 or 2.

    When PC2FLOP is run, the program prompts you to send the disk image file from the PC using the XMODEM protocol.

    Mike

  10. #10

    Default

    Thanks, I have Procomm running fine in my IBM5155 and a known good serial port. So far I have only used it in chat mode to send and receive ASCII for my Votrax type & talk project, not to send and entire program file though, but I should be able to figure that out. I'm ok on the hardware/connection side of serial ports.

    One thing though, with the Sol-20 computer and the North Star HDD controller card I have bought to go with it, there will possibly be hardware faults on that card. To reduce the probability of any additional faults in the actual drives themselves, I have splashed out bought two unused direct drive IBM YD-580 360kB 5.25" units, so that will help reduce the variables of old used drives and also bought the built and tested option of Mikes' VSG, so I know that will be working too. Also the IBM manuals for the YD-580's are on Minuszerodegrees which is very helpful.

    But it is still possible the North Star controller card could be defective. So if I had at least one known good 5.25" disk (created by a North Star controller & VSG disk drive system) with some working software on it, it would really help to test & verify and fault find my initial setup with the computer & drives.

    I notice on the SOL-20 and nearly all its S-100 cards, the fashion was to use dual wipe, rather than machined pin, IC sockets. At least the pins inside the socket area are protected from corrosion. Are these sockets known to give much trouble in the SOL-20 ? Is it better in the initial restoration the clean all the IC pins & sockets, lubricate them and re-fit the IC's ?

Bookmarks

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •