yenatch/bootstrap.gb

bootstrap.gb's Issues

Clearing VRAM on init

In Init: there are these two lines:

; Filling vram is not really necessary.
;	fill $8000, $2000, 0

On some emulators (VBA) and on a real Gameboy Color, the BG map is already all cleared, so filling VRAM is unnecessary. But on other emulators (BGB), the BG map has some artifacts in it, resulting in this:

Plus, if a game intentionally has a soft-reset option, it may be desirable to deliberately clear VRAM.
So for sanity, maybe this line should be un-commented.

RGB Macro Typo

db in RGB macro should be dw

FarCall bugs

In this snippet from rst.asm:

FarCall_:
	ld  [wFarCallHold + 0], a
	put [wFarCallHold + 1], h
	put [wFarCallHold + 2], l

	[ ... ]

	ld hl, wFarCallHold + 1
	ld a, [hli]
	ld h, [hl]
	ld l, a

This ends up swapping h and l
Could just put l before h

Also, at the end, this bit attempts to save the potential return value in a and/or f while pulling the rom bank off the stack, but leaves a hole in the stack:

	push af

	add sp, 2
	pop af ; hROMBank
	add sp, -4
	rst Bankswitch

	pop af
	ret

It needs an extra add sp, 2 at the end:

	push af

	add sp, 2
	pop af ; hROMBank
	add sp, -4
	rst Bankswitch

	pop af
	add sp, 2
	ret