05488: megadriv genesis: Genesis ROM is uneditable via command nor memory window

ID	Category [?]	Severity [?]	Reproducibility	Date Submitted	Last Update
05488	Debugger	Minor	Always	Apr 6, 2014, 02:36	Apr 8, 2014, 14:26

Tester	rimsky82	View Status	Public	Platform	MESS (Self-compiled)
Assigned To		Resolution	Open	OS	Windows Vista/7/8 (64-bit)
Status [?]	Confirmed			Driver	sega/mdconsole.cpp
Version	0.152	Fixed in Version		Build	64-bit
		Fixed in Git Commit		Github Pull Request #

Summary	05488: megadriv genesis: Genesis ROM is uneditable via command nor memory window
Description	Genesis ROM is uneditable. Whether using commands in the debugger or typing to the memory window, it won't change.
Steps To Reproduce	Play any game in Megadrive/Genesis with the debugger enabled and attempt to edit any words in the ROM range (0 - 0x3FFFFF I believe).
Additional Information	Not being able to edit the ROM during the game makes the emulator useless to try to hack the game to make new Game Genie codes or any other ASM related cheats. Including any MESS cheats that manipulate the ROM.
Github Commit

Flags
Regression Version
Affected Sets / Systems	megadriv genesis

Attached Files

No.10538 Tafoid Administrator Apr 6, 2014, 19:10 edited on: Apr 6, 2014, 19:17	Might it make a difference if you are loading the same via the normal "picker" style or are you using the softlist? I can confirm I cannot change the memory in that range with the debug interface, normally using maincpu.mw@address=value I suspect most of not all externally cart based systems are in the same boat as I had an issue dealing with PCE/TG-16 as well some months back.
No.10539 rimsky82 Tester Apr 6, 2014, 19:27	it doesn't seem to make a difference how it's loaded. (Verified with an md file on genesis). I will add that I think this might have started when the genesis was slotified a few months back. You may be right, that may have something to do with it.
No.10547 Kale Developer Apr 8, 2014, 13:25	As a rule of thumb, no ROM for any system can be edited from the debugger. And I know it too well because I've needed it in some circumstances and needed to resort to code it manually or use debug tricks. Debugger treats your memory writes as if the program is trying to write to ROM (which it fails for obvious reasons) Now, I'm not against this feature, but how to implement it?
No.10548 rimsky82 Tester Apr 8, 2014, 14:26	I may be misinformed, but I just want to be certain we are on the same page. I'm not trying to edit the ROM directly, say to the mdslot region, but rather to the ROM loaded in memory in the maincpu region. Whether or not that makes a difference, I don't know. I will also add this does work in other systems, such as nes, and it worked for genesis in the past, like was already stated, possibly before the system was slotified.