boot sector woes

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boot sector woes

Mdasoh Kyappd
this patch is a suggestion for the bootsector to boot on older (like my XT) machines
where the drive requires a few retries before loading a sector.  The resulting binary
might be too big actually.  In this case I would like a bit of help fitting it in there.

yours,
        - Mdasoh Kyaeppd

--- boot.ori/boot.asm   2017-01-30 02:08:55.835437500 -0700
+++ boot/boot.asm       2017-01-31 13:06:37.742679500 -0700
@@ -423,7 +423,7 @@
                                                 ; setup LBA disk block
                 mov     LBA_SECTOR_32,bx        ; bx is 0 if extended 13h mode supported
                 mov     LBA_SECTOR_48,bx
-
+               mov     si,1
                 mov     ah,042h
                 jmp short    do_int13_read

@@ -472,12 +472,20 @@
                 inc     cx                      ; make sector 1-based (1-63)

                 les     bx,[LBA_OFF]
+               mov     si,5
+do_chs_read:
                 mov     ax, 0x0201
 do_int13_read:
                 mov     dl, [drive]
-                int     0x13
-                jc      boot_error              ; exit on error
+                int     0x13                   ; read data from disk
+               jnc     did_int13_read

+               xor     ax,ax
+               int     0x13
+               dec     si
+                jz      boot_error              ; exit on error
+               jmp     do_chs_read             ; prod it a few times
+did_int13_read:
                 mov     ax, word [bsBytesPerSec]

                 push    di

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Re: boot sector woes

tom ehlert
am 1. Februar 2017 um 01:23 schrieben Sie:

> this patch is a suggestion for the bootsector to boot on older (like my XT) machines
> where the drive requires a few retries before loading a sector.  The resulting binary
> might be too big actually.

that is a clear indication that you did not test this.

why do you expect that we do YOUR work ?

Tom



> In this case I would like a bit of help fitting it in there.

> yours,
>         - Mdasoh Kyaeppd

> --- boot.ori/boot.asm   2017-01-30 02:08:55.835437500 -0700
> +++ boot/boot.asm       2017-01-31 13:06:37.742679500 -0700
> @@ -423,7 +423,7 @@
>                                                  ; setup LBA disk block
>                  mov     LBA_SECTOR_32,bx        ; bx is 0 if extended 13h mode supported
>                  mov     LBA_SECTOR_48,bx
> -
> +               mov     si,1
>                  mov     ah,042h
>                  jmp short    do_int13_read

> @@ -472,12 +472,20 @@
>                  inc     cx                      ; make sector 1-based (1-63)

>                  les     bx,[LBA_OFF]
> +               mov     si,5
> +do_chs_read:
>                  mov     ax, 0x0201
>  do_int13_read:
>                  mov     dl, [drive]
> -                int     0x13
> -                jc      boot_error              ; exit on error
> +                int     0x13                   ; read data from disk
> +               jnc     did_int13_read

> +               xor     ax,ax
> +               int     0x13
> +               dec     si
> +                jz      boot_error              ; exit on error
> +               jmp     do_chs_read             ; prod it a few times
> +did_int13_read:
>                  mov     ax, word [bsBytesPerSec]

>                  push    di

> ------------------------------------------------------------------------------
> Check out the vibrant tech community on one of the world's most
> engaging tech sites, SlashDot.org! http://sdm.link/slashdot
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Mit freundlichen Grüßen/Kind regards
Tom Ehlert
+49-241-79886


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