Search found 11 matches

by raq
Tue Jun 23, 2020 6:45 pm
Forum: Megadrive/Genesis
Topic: Most compatible way to jump to game image on hardware - making my own cart
Replies: 21
Views: 3460

Re: Most compatible way to jump to game image on hardware - making my own cart

Yep those initial 50% that worked before probably do what stef said or they use there on soft reset mechanism by a variable/flag in WRAM.
by raq
Sun Jun 21, 2020 6:44 pm
Forum: Megadrive/Genesis
Topic: Most compatible way to jump to game image on hardware - making my own cart
Replies: 21
Views: 3460

Re: Most compatible way to jump to game image on hardware - making my own cart

Hmmmm... Sonic - Return To The Origin seems to only work in fusion. Blastem comes up with a nice message for the same ROM:- [*] 'Read from VDP data port while writes are configured. CPU is now frozen. VDP Address 4, CD:5' Not much use I know but this suggests the hack is not accessing hardware corre...
by raq
Sun Jun 21, 2020 5:40 pm
Forum: Megadrive/Genesis
Topic: Most compatible way to jump to game image on hardware - making my own cart
Replies: 21
Views: 3460

Re: Most compatible way to jump to game image on hardware - making my own cart

Do these hacks work in emulation? Not the highly accurate ones :D The reason is I believe some of these hacks create exception errors by accident, the most common is reading or writing mis-aligned words, this will, at best! crash on actual hardware but can do other stange things. If the GR runs all ...
by raq
Sat Jun 20, 2020 4:12 pm
Forum: Megadrive/Genesis
Topic: Most compatible way to jump to game image on hardware - making my own cart
Replies: 21
Views: 3460

Re: Most compatible way to jump to game image on hardware - making my own cart

Glad it helped :D :D :D The reason to clear I/O control registers... Here is some code that SEGA asked all developers to use, pretty sure 95%+ of games use it. The full code is called ICD_BLK4 and its in the DTS archives somewhere. _ColdBoot: | tst.l 0x00a10008.l | on a power cycle MD hardware initi...
by raq
Fri Jun 19, 2020 11:48 am
Forum: Megadrive/Genesis
Topic: Most compatible way to jump to game image on hardware - making my own cart
Replies: 21
Views: 3460

Re: Most compatible way to jump to game image on hardware - making my own cart

Hi, you need to simulate a hard reset, see if the following helps, written in gnu as, must be executed in 68K WRAM .... code to switch banks move.w #0x2700,%sr | disable all interrupts sub.l %a0,%a0 | init pointer to beginning of ROM 0: move.w %a0,0x00a10008 | clear IO control move.l %a0,0x00a1000a ...
by raq
Fri Jan 09, 2015 7:45 pm
Forum: Mega/SegaCD
Topic: MegaCD2 Japan Bios on PAL MegaCD2
Replies: 23
Views: 15792

ooops, my mistake on too many zeroes :oops:

There is a bit in the config register of the everdrive thats set when a BIOS is flashed to the everdrive, so maybe the fpga traps addresses 0x20000 - 0x3ffff and 0x200000 - 0x23ffff and sets CART_IN high when in this range.
by raq
Sat Jan 03, 2015 2:07 pm
Forum: Mega/SegaCD
Topic: MegaCD2 Japan Bios on PAL MegaCD2
Replies: 23
Views: 15792

Isn't it the case when a cart is inserted the CD BIOS (the original one in the Mega-CD) gets mapped to 0x40000000 and cart is mapped to 0x00000000 and this swaps around when cart is removed?
by raq
Thu Jul 04, 2013 5:54 pm
Forum: Tools
Topic: aPLib decruncher for 68000
Replies: 48
Views: 33695

I see it now :oops:, nice trick, eliminates the need for a counter as well
by raq
Thu Jul 04, 2013 5:23 pm
Forum: Tools
Topic: aPLib decruncher for 68000
Replies: 48
Views: 33695

Ahhhh okay, so what your saying is that bit 0 is always set to 1? How come? is this part of the compression design?
by raq
Thu Jul 04, 2013 11:38 am
Forum: Tools
Topic: aPLib decruncher for 68000
Replies: 48
Views: 33695

Syntax Error

Think there may be a mistake in your optimization ; get_bit: Get bits from the crunched data (D3) and insert the most significant bit in the carry flag. get_bit: add.b d3,d3 ; move MSB to C and X bne.b still_bits_left ; error!!! what if we have an end sequence of 0 bits? move.b (a0)+,d3 ; Read next ...
by raq
Thu Apr 15, 2010 7:07 pm
Forum: Mega/SegaCD
Topic: Mega-CD UniBios
Replies: 4
Views: 6293

Mega-CD UniBios

Here is a 'hack' of the european Mega-CD BIOS v1.00 that bypasses the country code and CD protection. This is a very basic hack and there are a few 'glitches' with it. The two I know of (and can't do nothing about) are that if you use this BIOS on 60Hz machines (USA Genesis, JAP Mega Drive) there is...