Split BIOS/UEFI binaries for Pure64

[IanSeyler]

Prior to a few moments ago there was only one main Pure64 file (pure64.sys). This file contained the necessary code for booting on a BIOS-based and UEFI-based system.

It's desirable to keep the binary size of Pure64 small (it's already 6KiB) so it made sense to separate the BIOS and UEFI bits.

After using NASM for more than 10 years now, I finally looked into how its Conditional Assembly works. We now have one Pure64 code that can be built in two different ways. This makes sense as the UEFI version of Pure64 doesn't need the floppy driver of the BIOS version.

ReturnInfinity/Pure64#88

[zedas404-web]

Hello,
I am trying to test Pure64 boot using a test kernel in qemu as described in the Readme.md in the /docs folder in the Pure64 master.
I have a simple nasm kernel that just prints a message. I followed the instructions in the readme file replacing pure64.sys with pure64-bios.sys and mbr.sys by bios.sys. I also have qemu to direct the serial port to a file. I am not getting anything back just a clean screen and empty serial text file.
I padded my kernel to 4k.
I this method of using Pure64 to boot a kernel still the same? thanks

Here is what I am running:
#!/usr/bin/env bash

./clean.sh

./build.sh

nasm -f bin kernel.asm -o kernel.bin -l kernel.lst

dd if=/dev/zero of=disk.img count=128 bs=1048576
cat ./bin/pure64-bios.sys kernel.bin > software.sys
dd if=./bin/bios.sys of=disk.img conv=notrunc
dd if=software.sys of=disk.img bs=512 seek=16 conv=notrunc

qemu-system-x86_64 -machine q35 -smp cpus=2 -serial file:serial.txt -m 4G -vga std -drive format=raw,file=disk.img

[IanSeyler]

The issue here is that the BIOS version of Pure64 expects the software to be on sector 262160 since it is meant for a hybrid disk image. Technically this isn't required if you are doing BIOS-only.

This is configured in bios.asm:
%define DAP_STARTSECTOR 262160

1. Change that line in bios.asm to %define DAP_STARTSECTOR 16
2. ./build.sh
3. dd if=./bin/bios.sys of=disk.img conv=notrunc

For testing I used this:

kernel.asm:

[BITS 64]
[ORG 0x10000]

start:
	nop
	jmp start

I added this to the end of your qemu command:
-monitor telnet:localhost:8086,server,nowait

Then in another terminal execute:
telnet localhost 8086
Type info registers
You should see RIP in your kernel code (0x0000000000100000).

[zedas404-web]

Great. I will try that. Thank you.

…

On Sat, Aug 23, 2025 at 11:59 AM Ian Seyler ***@***.***> wrote: The issue here is that the BIOS version of Pure64 expects the software to be on sector 262160 since it is meant for a hybrid disk image. Technically this isn't required if you are doing BIOS-only. This is configured in bios.asm: %define DAP_STARTSECTOR 262160 1. Change that line in bios.asm to %define DAP_STARTSECTOR 16 2. ./build.sh 3. dd if=./bin/bios.sys of=disk.img conv=notrunc For testing I used this: kernel.asm: [BITS 64] [ORG 0x10000] start: nop jmp start I added this to the end of your qemu command: -monitor telnet:localhost:8086,server,nowait Then in another terminal execute: telnet localhost 8086 Type info registers You should see RIP in your kernel code (0x0000000000100000). — Reply to this email directly, view it on GitHub <#122 (reply in thread)>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/BWMG3WMWTN22HJ4673LKLFT3PCMVTAVCNFSM6AAAAABSPG2BJWVHI2DSMVQWIX3LMV43URDJONRXK43TNFXW4Q3PNVWWK3TUHMYTIMJZG44DIMA> . You are receiving this because you commented.Message ID: ***@***.*** .com>