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Format with write protect on...

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    Try formatting with IMD. See what it says. That might confirm issues with the BIOS, as IMD doesn't use it.


      Does IMD require DMA? My T1000 does not have DMA.


        Pretty sure I tried it on my DMA-less 1000hx and, yeah, no dice. One of the few programs that cares about that.
        My Retro-computing YouTube Channel (updates... eventually?): Paleozoic PCs Also: Blogspot


          Ah, okay, forget that one then.

          Given that the BIOS must be unique in this area, perhaps it is a BIOS issue. I don't suppose the source for the BIOS is available...


            I can dump it, isn't there a tool around here to do that?


              Sure, but dumping and disassembling to suss out the function are two very different matters.


                There are some disassemblies of several Tandy 1000 BIOSes here:


                But there's not a lot of work done yet on actually commenting them.
                My Retro-computing YouTube Channel (updates... eventually?): Paleozoic PCs Also: Blogspot


                  That looks pretty good Eudimorphodon! They have the int 13_05 function even picked out. Now if I can just understand it and how the 765 works!


                    Originally posted by alank2 View Post
                    ... and how the 765 works!
                    [This] may help.


                      I'm not following the code very well, I don't know x86 and/or its peripherals enough.

                      int 13 - ah 05 is supposed to return an error code in AH, but what looks like the end of the function:

                      f000:D0CB                 pushf
                      f000:D0CC                 push    ax
                      f000:D0CD                 call    get_diskette_params
                      f000:D0D0                 mov     al, es:[si+2]
                      f000:D0D4                 cli
                      f000:D0D5                 mov     ds:40h, al
                      f000:D0D8                 sti
                      f000:D0D9                 pop     ax
                      f000:D0DA                 and     byte ptr ds:3Eh, 7Fh
                      f000:D0DF                 popf
                      f000:D0E0                 pop     es
                      f000:D0E1                 pop     ds
                      f000:D0E2                 pop     bp
                      f000:D0E3                 pop     di
                      f000:D0E4                 pop     si
                      f000:D0E5                 pop     dx
                      f000:D0E6                 pop     cx
                      f000:D0E7                 pop     bx
                      f000:D0E8                 retf    2


                        That bit of code seems to do little more than reset the motor time out and clear the interrupt pending flag.

                        The Phoenix books on the PC CBIOS are very useful. If this is the complete 13h/05 request code, the actual formatting must take place in the FORMAT.COM program itself. Have you tried to run it on a standard PC?


                          Do you mean running the MS-DOS 6.22 format program on another PC? It fails immediately.


                            For whatever it's worth I don't think I've had any issues with any version of DOS formatting disks on my DMA-less 1000 EX and HX, so I'm kind of skeptical of this being a BIOS issue. For sanity's sake I just tried doing a "format a:/u /s" on my HX with PC-DOS 7/2000 (which should share most if not all of its code with MS-DOS) and it worked without a problem.

                            (I don't have a physical disk drive hooked up to it but it was able to format an image on the Gotek+Flashfoppy.)

                            For laughs I tried yanking the USB stick out of the gotek in the middle of the format; the result was a "Not ready; Format terminated". I assume it must detect that state by reading "something" during the format since these machines don't have diskchg/READY support? (Line 34 is NC on the floppy header.) But whether whatever its doing is verifying the format of tracks it just wrote or what, I have no idea.
                            My Retro-computing YouTube Channel (updates... eventually?): Paleozoic PCs Also: Blogspot


                              Originally posted by alank2 View Post
                              Do you mean running the MS-DOS 6.22 format program on another PC? It fails immediately.
                              ...on another PC running 6.22? What's the error message?


                                Perhaps someone else with a Tandy 1000 or 1000A could try to format a write protected disk at some point.