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‎.gitignore

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*.bin
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*.rom
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*.img
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*.kate-swp
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*.86
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*.386
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optromloader9
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optromloader15
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optromloader18

‎LICENSE

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MIT License
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Copyright (c) 2021 Roc Vallès i Domènech
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Permission is hereby granted, free of charge, to any person obtaining a copy
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of this software and associated documentation files (the "Software"), to deal
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in the Software without restriction, including without limitation the rights
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to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
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copies of the Software, and to permit persons to whom the Software is
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furnished to do so, subject to the following conditions:
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The above copyright notice and this permission notice shall be included in all
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copies or substantial portions of the Software.
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THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
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AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
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LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
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OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
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SOFTWARE.

‎Makefile

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fasm = fasm
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#hexdumpcmd = hexdump -C
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hexdumpcmd = xxd -a
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qemu = qemu-system-i386
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date = \"`date +%Y%m%d%H%M`\"
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.PHONY: all
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all: hexdump optromloader18 optromloader15 optromloader9 fd1440.img fd720.img fd1200.img fd360.img
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optromloader18: optromloader.S
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@echo "*** assembling $@..."
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$(fasm) -d date=$(date) -d sectorspertrack=18 optromloader.S $@
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optromloader15: optromloader.S
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@echo "*** assembling $@..."
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$(fasm) -d date=$(date) -d sectorspertrack=15 optromloader.S $@
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optromloader9: optromloader.S
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@echo "*** assembling $@..."
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$(fasm) -d date=$(date) -d sectorspertrack=9 optromloader.S $@
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fd1440.img: optromloader18 optrom.bin
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@echo "*** building $@..."
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cat optromloader18 optrom.bin | dd bs=1474560 conv=sync of=$@
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fd720.img: optromloader9 optrom.bin
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@echo "*** building $@..."
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cat optromloader9 optrom.bin | dd bs=737280 conv=sync of=$@
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fd1200.img: optromloader15 optrom.bin
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@echo "*** building $@..."
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cat optromloader15 optrom.bin | dd bs=1228800 conv=sync of=$@
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fd360.img: optromloader9 optrom.bin
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@echo "*** building $@..."
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cat optromloader9 optrom.bin | dd bs=368640 conv=sync of=$@
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.PHONY: clean
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clean:
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@echo "*** Removing build artifacts..."
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rm -f optromloader9 optromloader15 optromloader18 fd1440.img fd720.img fd1200.img fd360.img
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.PHONY: hexdump
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hexdump: optromloader18
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@echo "*** hexdump optromloader18..."
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$(hexdumpcmd) optromloader18
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.PHONY: emulate
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emulate: fd1440.img
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@echo "*** Emulating with qemu..."
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$(qemu) -drive if=floppy,format=raw,index=0,file=fd1440.img
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.PHONY: emulaterom
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emulaterom: optrom.bin
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@echo "*** Emulating with qemu..."
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$(qemu) -net none -option-rom optrom.bin

‎README.md

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# optromloader: IBM PC/Clone 8086+ floppy-loading of option roms.
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Booted from a floppy, it will load an Option ROM image into the end of conventional memory.
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![PCem PC1512 screenshot](https://b.rvalles.net/unsorted/pcem_pc1512_optromboot_xtide.png)
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Usage
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* Ensure fasm (flat assembler) is installed
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* Copy your ROM image as the `optrom.bin` file.
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* Run `make`.
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* Optionally test with qemu: `make emulate`.
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* Floppy images will be created (fd*.img).
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* Alternatively, use a binary release. Concatenate:
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* optromloader9/15/18 (according to sectors per track in your floppy format)
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* 9 for 5.25" 360K and 3.5" 720K
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* 15 for 5.25" 1.2M
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* 18 for 3.5" 1.44M
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* the ROM image.
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* pad to floppy size.
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Use cases (non-exhaustive)
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* Test boot ROMs before burning them.
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* Netboot with etherboot/gpxe/ipxe.
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* IDE support (including LBA!) with XTIDE Universal BIOS.
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Highlights
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* flat assembler syntax.
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* Pure 8086 code.
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* Works on newer hardware, such as the 486 I wrote it for.
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* Fits in a floppy bootblock.
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* Trivial to use. Concatenate loader and the ROM image, write into floppy.
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* Makefile will prepare 5.25" 360K/1.2M and 3.5" 720K/1.44M floppy images.
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Caveats
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* Hardcoded to use the first floppy drive.
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* ROM checksum isn't checked (yet).
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* Always ensure a boot ROM is signed before burning.
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* Qemu provides a python tool to sign ROMs:
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* https://github.com/qemu/qemu/blob/master/scripts/signrom.py
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* For XTIDE Universal BIOS roms, use its XTIDECFG tool to configure and sign ROM images.

‎optromloader.S

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;optromloader, by Roc Valles Domenech.
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;MIT license, see LICENSE for details.
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;https://www.rvalles.net
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format binary as "raw"
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use16
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org 7C00h
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jmp 0x0000:start
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start:
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mov sp,$7C00
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mov ax,0
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mov bx,ss
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mov ss,ax
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mov ds,ax
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mov si,banner_str
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call printstr
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mov ax,1
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mov bx,bootblock_end
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call readblock
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mov bx,[bootblock_end]
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cmp bx,$AA55
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jnz bad_header_magic
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mov si,romsize_str
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call printstr
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mov ax,0
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mov al,[bootblock_end+2]
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mov bx,ax
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call printhex8
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mov si,romsizebytes_str
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call printstr
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mov ax,bx
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mov cl,9
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shl ax,cl
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call printhex16
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mov si,ramsize_str
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call printstr
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int 12h
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call printhex16
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mov dx,bx
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test dx,1
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jz .blocks_even
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add dx,1
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.blocks_even:
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shr dx,1
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sub ax,dx
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mov [1043],ax
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mov si,ramsizeafter_str
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call printstr
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int 12h
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call printhex16
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mov cl,6
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shl ax,cl ;target segment
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mov es,ax
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mov dx,0
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mov si,readblocks_str
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call printstr
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mov cx,bx
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mov bx,0 ;target address
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.readrom:
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;hlt
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add dl,1
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mov ax,dx
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call printhex8
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call readblock
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add bx,512
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mov si,readblocksbs_str
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call printstr
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cmp cx,dx
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jne .readrom
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;mov si,cksum_str
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;call printstr
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mov ax,es
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mov [.calloptrom+3], ax
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mov ah,0eh
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mov al,'#'
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int 10h
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;sti ;some bad BIOSs disable on int13 and forget to restore.
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.calloptrom:
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call 0xA000:3
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mov ah,0eh
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mov al,'@'
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int 10h
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int 19h
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;*****************************************************************************
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bad_header_magic:
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mov si,bad_header_magic_str
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call printstr
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mov ax,bx
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call printhex16
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jmp $
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printstr: ;SI *str
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push ax
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mov ah,0eh ;print character
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.printstr_loop:
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lodsb ;SI++ -> al
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test al,al
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jz .printstr_end
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int 10h ;print
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jmp .printstr_loop
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.printstr_end:
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pop ax
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ret
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;FIXME: these value dumpers could be shorter.
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printhex8: ;AL (preserved) value to print
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push ax
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push bx
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push cx
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mov ah,0eh
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mov bl,al
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mov cl,4
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rol bl,cl ;in 8086, 1 or cl. 186+ for higher imm.
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call printhexdigit
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rol bl,cl
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call printhexdigit
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pop cx
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pop bx
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pop ax
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ret
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printhex16: ;AX (preserved) value to print
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push ax
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push bx
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push cx
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mov bx,ax
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mov ah,0eh
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mov cl,4
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rol bx,cl
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call printhexdigit
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rol bx,cl
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call printhexdigit
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rol bx,cl
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call printhexdigit
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rol bx,cl
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call printhexdigit
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pop cx
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pop bx
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pop ax
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ret
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printhexdigit: ;FIXME: Make shorter. possibly use daa/adc inst.
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mov al,bl
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and al,$F
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add al,$30
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cmp al,$3A
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jb .printhexlow
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add al,7
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.printhexlow:
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int 10h
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ret
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resetfloppy:
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mov ah,0
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mov dl,0
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int 13h
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ret
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readblock: ;AX blocknumber, ES:BX (preserved) addr.
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;call printhex16
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;xchg ax,bx
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;call printhex16
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;xchg ax,bx
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push cx
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push dx
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;CHS magic: get number of tracks, heads>>1 is cyl
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mov dl,sectorspertrack
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div dl ;ax/dl -> /al, %ah
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mov dh,0 ;head 0..15
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test al,1
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jz .heads_even
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add dh,1
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.heads_even:
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shr al,1
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;CX 0-5 sector, 6-7 track MSB, 8-15 track LSB
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mov ch,al ;cyl
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add ah,1 ;CHS sectors start at 1
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mov cl,ah ;sector
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mov ah,02h ;BIOS 13h read CHS block
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mov al,1 ;sectors to read 1..128
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mov dl,0 ;drive 0=A 80h=hdd0
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;xchg ax,cx
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;call printhex16
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;xchg ax,cx
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;xchg ax,dx
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;call printhex16
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;xchg ax,dx
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push ax
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.retry:
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;hlt
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;push ax
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;mov ah,0eh
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;mov al,'%'
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;int 10h
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;pop ax
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int 13h
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;push ax
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;mov ah,0eh
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;mov al,'?'
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;int 10h
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;pop ax
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cmp ah,0
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jne .error
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;mov dx,es
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;mov ds,dx
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;mov ax,[bx]
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;call printhex16
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mov dx,0
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mov ds,dx
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pop ax
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pop dx
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pop cx
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ret
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.error:
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push ax
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mov ah,0eh
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mov al,'E'
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int 10h
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pop ax
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mov al,ah
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mov ah,0
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call printhex8
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call resetfloppy
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mov si,readblocks_str
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call printstr
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pop ax
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push ax
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jmp .retry
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banner_str: db "optromloader, by Roc Valles Domenech <rvalles.net>, built ",date,'.',13,10,0
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bad_header_magic_str: db "Ehdrmagic:",0
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romsize_str: db "ROM blks:",0
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romsizebytes_str: db "->",0
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ramsize_str: db 13,10,"RAM:",0
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ramsizeafter_str: db "/",0
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readblocks_str: db 13,10,"Rd:",0
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readblocksbs_str: db 8,8,0
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;readblocksbs_str: db 13,10,"Rd+",0
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;cksum_str: db 13,10,"Ck+",0
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.finalize_bootblock:
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times 510-($-$$) db 0
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dw $AA55
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bootblock_end:

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