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Thread: AT&T PC6300 Storage Configuration

  1. #11
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    Quote Originally Posted by Chuck(G) View Post
    See P13 of the schematic,
    I would like to find the schematic. I didn't find one in the Service Manual; did I miss something?

    But I will leave the data rate as is, for now at least, and explore other options.

    -CH-

  2. #12

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    2M-XBIOS also supports 1.2 MB floppies as well as the 3" 2.88 MB ED floppies.
    PM me if you're looking for 3" or 5" floppy disks. EMail For everything else, Take Another Step

  3. #13
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    Quote Originally Posted by clh333 View Post
    I would like to find the schematic. I didn't find one in the Service Manual; did I miss something?
    http://bitsavers.trailing-edge.com/p...tion_Nov84.pdf

    At the end, all the schematics are there - they are very useful.

  4. #14
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    Comments:

    1 - It's not necessary to introduce AT&T 6300, Xerox 606x and M24 here in this forum. This is the mostly bespoken machine here in the forum after the IBM 51xx machines. Here and everywhere else, I talk about M24, shorter to write, but it also means M24SP (10 Mhz), M21 (portable), AT&T 6300 and Xerox 606x machines. Their successor is M240, AT&T 6300WGS, which has more compatible floppy controller on completely redesigned (smaller) mainboard, 10 Mhz 8086, graphics card, different bus-converter card)

    2. Why bigger floppy drives? Software for even fast XTs never came on HD floppy. For imaging disks suitable for XT the support of 360/640/720 kb drives of M24 BIOS is there (please note that for 720 kB you may need to add the driveparm command in config.sys as BIOS may assumes 8 sectors instead of 9 if you select 80 track drive via DIP switch). Please note, that if you write image 40 track 5,25 inch disks using a 1.2 MB HD drive, you might get trouble reading the disks cleanly in 40 tracks drives. This is because the magnetic line written by a HD drive is thinner than from a 40 track drive, so it can lay inside of a previously written track made by a 40 track drive as such old drives would see the thinner line from HD drive and outer older thicker track line from SD drive at the same time. Some 40 track drives will not read that accurate. So, better stay at the 40 tracks drive, and have an AT or better with the HD drives... M24 also can also support those rare doublesided 80 tracks single density drives, 640 or 720 kb, they are also mostly fine for writing 40 track disks.

    Fun fact: The M24 and it's derivates have been designed by well known italian industrial design pope Ettore Sottsass, see https://en.wikipedia.org/wiki/Ettore_Sottsass. For design purists, if you plug in a floppy drive which has not been used by Olivetti / AT&T / Xerox, you break that valuable design of the machine.

    3. Alternative BIOS is not enough to support HD floppys in M24. The onboard FDC can only support low or high density data rates, not switchable by software. When set to HD, the machine could not read low density disks anymore. I think also the BIOS has limitations, never tryed, but I think it can not support disks with more than 9..11 secors (HD is 18..22 sectors). So booting from such disks not possible as you have to add the driveparm parameters to config.sys for HD drive. If you like to do that, try to get Olivetti M240 or it's realbeled AT&T version, I think, it's 6300WGS. M240 BIOS officially supports HD drives. And M240 is better for compatibility with many RAW floppy tools, like IMD, teledisk, etc. (See my topic about M24 and IRQ issue with some floppy tools here in the forum)

    4. Would the Adaptec 1542 with it's high AT-IRQs work in M24 which only has 8 Bit ISA (it has 16 bit, but the upper 8 bit are proprietary connector) (XT IRQ is from 0-8, while AT IRQ is 0 to 15, with XT-IRQ 2 cascaded to AT-IRQ 9)

    5. Use XT-IDE as the mass storage card, with two CF cards, one internally, one monted to an unused ISA slot bracked, that you can access it from the outside. So you have the 2nd CF for data transfer, just unplug it from M24 and plug to your modern computer. Note, that XT-IDE is not hotplug, so you need to reboot the M24 after such action. Proposed to use MS-Dos 5 or better to have useable big partitions. On the swapable 2nd CF use only one partition unless your modern computer runs Windows 10. Older Windows versions will not detect more than the 1st partition on removeable media.

    6. Also an interesting option for data transport between M24 and modern computer is using a 100 MB ZIP drive. You additionally need also an USB ZIP drive for your modern computer. Maybe, never tryed, also JAZ drives etc. would do the job. Additionally, your M24 must run MS-DOS 5.0 or better (originally M24 was delivered with MS-DOS 3.2x and older, and that can not support partitions bigger than 32 MB), and you need to swap the 8086 CPU by a NEC V30 8 Mhz CPU. This is because GUEST.EXE from IOMEGA only works with V30 or better, not with 8088/8086. Advantage over cold swap CF card is, that it is hot swapable. But it's slower. I use that way very often. I was not able until now to get the PALMZIP driver for ZIP drive to work on M24, the driver seems to have trouble with M24's parallel port (M240 might be better here, not tryed).
    Last edited by 1ST1; December 3rd, 2019 at 07:21 AM.

  5. #15
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    Quote Originally Posted by Valerio View Post
    http://bitsavers.trailing-edge.com/p...tion_Nov84.pdf

    At the end, all the schematics are there - they are very useful.
    Thank you; I had looked at Bitsavers but obviously in the wrong place.

  6. #16
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    I'll go out on a limb here just to be contrary.

    Back in the day when the AT was still new, folks were interested in getting 1.2M HD capability on their XTs, which vastly outnumbered ATs then. A company called Weltech introduced a drive that spun the media at 180 RPM so that it could be used with the native PC/XT controller. It was a terrible idea, when you consider that the induced signal in a (floppy) drive head is proportional to the linear speed of the medium. With some added software, you could convince your XT that it had a working 1.2M drive.

    It was a flash in the pan; reliability was awful. However, I've seen some of the Amiga folks opting to create dual-speed 3.5" drives...

  7. #17
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    Quote Originally Posted by 1ST1 View Post
    Comments:

    1 - It's not necessary to introduce AT&T 6300, Xerox 606x and M24 here in this forum. This is the mostly bespoken machine here in the forum after the IBM 51xx machines. Here and everywhere else, I talk about M24, shorter to write, but it also means M24SP (10 Mhz), M21 (portable), AT&T 6300 and Xerox 606x machines. Their successor is M240, AT&T 6300WGS, which has more compatible floppy controller on completely redesigned (smaller) mainboard, 10 Mhz 8086, graphics card, different bus-converter card)

    2. Why bigger floppy drives? Software for even fast XTs never came on HD floppy. For imaging disks suitable for XT the support of 360/640/720 kb drives of M24 BIOS is there (please note that for 720 kB you may need to add the driveparm command in config.sys as BIOS may assumes 8 sectors instead of 9 if you select 80 track drive via DIP switch). Please note, that if you write image 40 track 5,25 inch disks using a 1.2 MB HD drive, you might get trouble reading the disks cleanly in 40 tracks drives. This is because the magnetic line written by a HD drive is thinner than from a 40 track drive, so it can lay inside of a previously written track made by a 40 track drive as such old drives would see the thinner line from HD drive and outer older thicker track line from SD drive at the same time. Some 40 track drives will not read that accurate. So, better stay at the 40 tracks drive, and have an AT or better with the HD drives... M24 also can also support those rare doublesided 80 tracks single density drives, 640 or 720 kb, they are also mostly fine for writing 40 track disks.

    Fun fact: The M24 and it's derivates have been designed by well known italian industrial design pope Ettore Sottsass, see https://en.wikipedia.org/wiki/Ettore_Sottsass. For design purists, if you plug in a floppy drive which has not been used by Olivetti / AT&T / Xerox, you break that valuable design of the machine.

    3. Alternative BIOS is not enough to support HD floppys in M24. The onboard FDC can only support low or high density data rates, not switchable by software. When set to HD, the machine could not read low density disks anymore. I think also the BIOS has limitations, never tryed, but I think it can not support disks with more than 9..11 secors (HD is 18..22 sectors). So booting from such disks not possible as you have to add the driveparm parameters to config.sys for HD drive. If you like to do that, try to get Olivetti M240 or it's realbeled AT&T version, I think, it's 6300WGS. M240 BIOS officially supports HD drives. And M240 is better for compatibility with many RAW floppy tools, like IMD, teledisk, etc. (See my topic about M24 and IRQ issue with some floppy tools here in the forum)

    4. Would the Adaptec 1542 with it's high AT-IRQs work in M24 which only has 8 Bit ISA (it has 16 bit, but the upper 8 bit are proprietary connector) (XT IRQ is from 0-8, while AT IRQ is 0 to 15, with XT-IRQ 2 cascaded to AT-IRQ 9)

    5. Use XT-IDE as the mass storage card, with two CF cards, one internally, one monted to an unused ISA slot bracked, that you can access it from the outside. So you have the 2nd CF for data transfer, just unplug it from M24 and plug to your modern computer. Note, that XT-IDE is not hotplug, so you need to reboot the M24 after such action. Proposed to use MS-Dos 5 or better to have useable big partitions. On the swapable 2nd CF use only one partition unless your modern computer runs Windows 10. Older Windows versions will not detect more than the 1st partition on removeable media.

    6. Also an interesting option for data transport between M24 and modern computer is using a 100 MB ZIP drive. You additionally need also an USB ZIP drive for your modern computer. Maybe, never tryed, also JAZ drives etc. would do the job. Additionally, your M24 must run MS-DOS 5.0 or better (originally M24 was delivered with MS-DOS 3.2x and older, and that can not support partitions bigger than 32 MB), and you need to swap the 8086 CPU by a NEC V30 8 Mhz CPU. This is because GUEST.EXE from IOMEGA only works with V30 or better, not with 8088/8086. Advantage over cold swap CF card is, that it is hot swapable. But it's slower. I use that way very often. I was not able until now to get the PALMZIP driver for ZIP drive to work on M24, the driver seems to have trouble with M24's parallel port (M240 might be better here, not tryed).
    Responses:

    1: M24 it is, then. I knew of the existence of the M24SP, but did not know the differences in design.

    2: I'll have to check, but I think some of the software distribution floppies that I have are 5.25 HD. In any event I have a number of machines that have the HD drives on them, the M240 being one of them, and a number of spare 5.25" 1.2 Mb drives. Yes, it's a bastardization to introduce the higher capacity 5.25 drive into the M24, but one that is invisible to the untrained eye. You might make the same objection about including an XT-IDE. In any case it's not as obvious as cutting a hole in the front panel and adding a 3.5" drive.

    3, 4 & 6: Clearly the M24's BIOS and FDC are limiting factors, and the Adaptec 1542, being a 16-bit card, will present difficulties, as I discovered this morning. But I have a Seagate ST2 SCSI adapter as well and that is eight-bit, has floppy as well as SCSI connectors and supports higher-density drives. Having a SCSI controller allows me to use external SCSI devices, such as the ZIP drive, of which I have several. I used to have an AGFA scanner that used SCSI, as well as a very early CD writer from Philips. I don't like the parallel or USB ZIP drives, but I do have JAZ and Bernoullis. The M24 already has an NEC swap.

    5: Yes, I plan to use the XT-IDE as the main storage device. I don't know about adding a second CF card to the XT-IDE; I was just going to run a cable from the XT-IDE header to a bracket.

    But all of this is tabled for the moment as the M24 is back to non-POST as of this morning. Grinding my teeth...

    -CH-

  8. #18
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    Quote Originally Posted by clh333 View Post
    In any case it's not as obvious as cutting a hole in the front panel and adding a 3.5" drive.
    No cutting necessary - just a drive bay adapter

    D176A175-51AB-4238-BC86-B678967378B1.jpeg

  9. #19
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    Quote Originally Posted by Valerio View Post
    No cutting necessary - just a drive bay adapter
    Seconded. Even though I'm the current owner of the "cut a hole in the front panel" 6300, I don't recommend it.

    Not sure if this is/isn't a good thread to mention this in, but I've had reliability issues with a 720K drive in my 6300. It appears to work fine after the typical config.sys "DRIVPARM=/d:1 /f:2 /t:80" line, but I have random silent bit errors that go undetected by DOS even with VERIFY=ON. So, I only use the 720k drive in my 6300 to read .zip files, where it will be obvious if it bit has flipped (pkunzip will complain). I've never been able to nail down what the trouble is.
    Offering a bounty for:
    - A working Sanyo MBC-775, Olivetti M24, or Logabax 1600
    - Music Construction Set, IBM Music Feature edition (has red sticker on front stating IBM Music Feature)

  10. #20
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    Quote Originally Posted by clh333 View Post
    Responses:

    5: Yes, I plan to use the XT-IDE as the main storage device. I don't know about adding a second CF card to the XT-IDE; I was just going to run a cable from the XT-IDE header to a bracket.
    This is quite easy, Most of the IDE-2-CF adapter have a Master/Slave jumper, just like IDE harddisks have. There are dual IDE-2-CF-adapters where one CF slot is hardwired to master, the other as slave.

    Quote Originally Posted by clh333 View Post
    Responses:

    2: I'll have to check, but I think some of the software distribution floppies that I have are 5.25 HD. In any event I have a number of machines that have the HD drives on them, the M240 being one of them, and a number of spare 5.25" 1.2 Mb drives. Yes, it's a bastardization to introduce the higher capacity 5.25 drive into the M24, but one that is invisible to the untrained eye. You might make the same objection about including an XT-IDE. In any case it's not as obvious as cutting a hole in the front panel and adding a 3.5" drive.
    So as you have, use thge M240 for HD drivces. This one has perfect support for HD drives. The only issue is that with writing 40 tracks disks with the HD drive. For some target drives to read these disks, mostly very old ones, this is not satisfying.

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