Detecting the bios
Moderator: BigEvilCorporation
Detecting the bios
hello all
I was thinking a bit about the md homebrewn legality, knowing that the megadrive is back on track commercialy with all those virtual consoles and megadrive compilation game.
What's worrying me is the message "produced or licensed by sega" which is displayed by the md2 bios... Maybe you don't know, but on the dreamcast scene, it was used to display a screen which deny that previous sentence. Is there a way to detect that the rom was launched by the bios and so display a denying sentence ?
Maybe by checking the version register, but i don't know if version 1 is really a md2 with bios or just the revision of md1 with the protection scheme, and it seems a bit inaccurate.
thanks in advance ^^
I was thinking a bit about the md homebrewn legality, knowing that the megadrive is back on track commercialy with all those virtual consoles and megadrive compilation game.
What's worrying me is the message "produced or licensed by sega" which is displayed by the md2 bios... Maybe you don't know, but on the dreamcast scene, it was used to display a screen which deny that previous sentence. Is there a way to detect that the rom was launched by the bios and so display a denying sentence ?
Maybe by checking the version register, but i don't know if version 1 is really a md2 with bios or just the revision of md1 with the protection scheme, and it seems a bit inaccurate.
thanks in advance ^^
-
- Very interested
- Posts: 3131
- Joined: Thu Nov 30, 2006 9:46 pm
- Location: France - Sevres
- Contact:
Re: Detecting the bios
A "safe" solution could be to always display the message :pPascal wrote:hello all
I was thinking a bit about the md homebrewn legality, knowing that the megadrive is back on track commercialy with all those virtual consoles and megadrive compilation game.
What's worrying me is the message "produced or licensed by sega" which is displayed by the md2 bios... Maybe you don't know, but on the dreamcast scene, it was used to display a screen which deny that previous sentence. Is there a way to detect that the rom was launched by the bios and so display a denying sentence ?
Maybe by checking the version register, but i don't know if version 1 is really a md2 with bios or just the revision of md1 with the protection scheme, and it seems a bit inaccurate.
thanks in advance ^^
I'm not sure about the version register...
Re: Detecting the bios
and simple !!!Stef wrote:A "safe" solution
Last edited by ob1 on Tue Jan 16, 2007 8:08 pm, edited 1 time in total.
-
- Very interested
- Posts: 2440
- Joined: Tue Dec 05, 2006 1:37 pm
- Location: Estonia, Rapla City
- Contact:
Try my TMSS patcher on your ROM, I have noticed, that patched ROMs will run, but the "produced by ..." message does not appear.
Mida sa loed ? Nagunii aru ei saa
http://www.tmeeco.eu
Files of all broken links and images of mine are found here : http://www.tmeeco.eu/FileDen
http://www.tmeeco.eu
Files of all broken links and images of mine are found here : http://www.tmeeco.eu/FileDen
-
- Very interested
- Posts: 2440
- Joined: Tue Dec 05, 2006 1:37 pm
- Location: Estonia, Rapla City
- Contact:
Yes it will crash the early MDs but that utility is for running old games on new MDs (Alex Kidd for example). I didn't make it check if newer system is used as I thought that the code gets too big and won't fit in the header.Pascal wrote:EDIT oki, you always write it, are you sure it won't crash on early MD ? coz that reg adress is maybe write only
If you reset the system, "produced by..." does not appear, maybe the BIOS thinks that everything is already set up and reset happened and nothing needs to be displayed ?
Mida sa loed ? Nagunii aru ei saa
http://www.tmeeco.eu
Files of all broken links and images of mine are found here : http://www.tmeeco.eu/FileDen
http://www.tmeeco.eu
Files of all broken links and images of mine are found here : http://www.tmeeco.eu/FileDen
-
- Very interested
- Posts: 2440
- Joined: Tue Dec 05, 2006 1:37 pm
- Location: Estonia, Rapla City
- Contact:
I'm not so sure about it, I'll ask Deven Gallo, he owns $h1Tload of MDs.ob1 wrote:This address is read only, only on the first model of Genesis. It was a prototype and was not released. Thus, we can consider that $A14000 will always be writable.
My pirate MD1 (which fried quite some time ago) would have probably crashed as that thing didn't have any BIOS and it's components had identical pinouts with the ones used in early real MDs It was VERY well done copy which acted EXACTLY like my real MD2 now.
Mida sa loed ? Nagunii aru ei saa
http://www.tmeeco.eu
Files of all broken links and images of mine are found here : http://www.tmeeco.eu/FileDen
http://www.tmeeco.eu
Files of all broken links and images of mine are found here : http://www.tmeeco.eu/FileDen
In his Sega Genesis hardware notes (http://cgfm2.emuviews.com/txt/gen-hw.txt), Charles MacDonald states
- Games must write the text 'SEGA' to A14000h if the lower four
bits of the version register return 01h.
- Writing 01h to A14101h disables the OS ROM and swaps in the cart ROM.
- The OS ROM checks for 'SEGA' or ' SEGA' at offset 100h in the cart ROM.
-
- Very interested
- Posts: 2440
- Joined: Tue Dec 05, 2006 1:37 pm
- Location: Estonia, Rapla City
- Contact:
More correct would be : Must write "SEGA" if the version reg returns <> 0
MDs without BIOS exist, why else I wrote the TMSS patcher
MDs without BIOS exist, why else I wrote the TMSS patcher
Mida sa loed ? Nagunii aru ei saa
http://www.tmeeco.eu
Files of all broken links and images of mine are found here : http://www.tmeeco.eu/FileDen
http://www.tmeeco.eu
Files of all broken links and images of mine are found here : http://www.tmeeco.eu/FileDen