Super Magic Drive research thread

Ask anything your want about Megadrive/Genesis programming.

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KanedaFr
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Post by KanedaFr » Tue Jul 19, 2011 9:49 pm

I added my Magic Drive schematic on the SMD page.

Now working on the RAM boards ;)

Chilly Willy
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Post by Chilly Willy » Wed Jul 20, 2011 3:29 am

I know it's a bit off topic, but if I had been making the SEGA CD, it would look just like the SMD. Look at an image of a SMD and tell me you don't think "CD" right off the bat. Have it flip open right in the middle with the circuit board above the CD with the cart slot attached so it's right where the cart slot in the SMD is. Plugging in the cart slot would have made the CD more flexible and given the chance to put a simple 256 color framebuffer in it for improved graphics.

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Post by TascoDLX » Wed Jul 20, 2011 7:06 am

Yes, my immediate thought looking at the SMD is Jaguar CD. Is that it?

I don't care to be the one to second-guess the Sega CD. But with a framebuffer and improved color depth, it would have been quite intriguing -- a whole different ballgame, even. It's a nice fantasy. That said, I kinda enjoy the system for what it is.

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Post by Chilly Willy » Wed Jul 20, 2011 11:09 pm

TascoDLX wrote:Yes, my immediate thought looking at the SMD is Jaguar CD. Is that it?
Exactly. You can't look at the SMD and not think it... well, in my opinion, at least. I think it looks cooler than either the model 1 or 2 CD as well.

I don't care to be the one to second-guess the Sega CD. But with a framebuffer and improved color depth, it would have been quite intriguing -- a whole different ballgame, even. It's a nice fantasy. That said, I kinda enjoy the system for what it is.
I don't think the extra 68000 was really needed - just ram for the MD CPU to use for programs/data loaded from CD, and the ASIC/framebuffer. Kinda on the fence about the PCM chip. They could have left it out if they wished to keep the price down. I think SEGA only added it because the PCE CD had an ADPCM chip in it.

Koji
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Post by Koji » Sat Jan 07, 2012 8:26 pm

Quick question, is there a SMDutil for dummies? ("how to")..I ask because I just can't seem to be able to make it work with my Super Magic Drive parallel port at all...

I'd like to dump the SMD "Magic Driver V-1" bios that I have, with it...

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KanedaFr
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Post by KanedaFr » Sun Jan 08, 2012 7:42 am

did you try with ucon64 ?

Koji
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Post by Koji » Sun Jan 08, 2012 7:57 am

Not yet, but I must be doing something wrong though..How do I go at installing something like io.dll (on windows xp) for example?...

I just figured SMDutil is the way to go when it comes to the SMD no?..

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KanedaFr
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Post by KanedaFr » Sun Jan 08, 2012 2:56 pm

I stopped fighting with LPT port on windows , I use a linux just for this.

Else, look at ucon64 page, there is a LPT driver for windows which I remember I used before
(http://ucon64.sourceforge.net/) and I think you should be able to get info from their faq

If you succeed, don't forget to send it to me so I can disassemble it :lol:

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Post by greatfunky » Fri Feb 03, 2012 12:27 pm

Hi all !
I realized today that i have a smd with an undumped/unknown bios 3.3C .
So i have dumped it with my double pro fighter .
Image

the difference between 3.3 & 3.3c : in the menu "load file , save file " is back again like in 3.1g version !
https://rapidshare.com/files/458231229/bios3.3c.rar

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KanedaFr
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Post by KanedaFr » Sat Feb 04, 2012 2:03 am

disassembly as soon as possible ;)

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Post by KanedaFr » Fri May 25, 2012 11:26 pm

I'm back to the office so I was able to take some times for this :twisted:
http://gendev.spritesmind.net/files/bsy ... alysis.zip

Not a lot of new stuff :
- (re)add the way to load/dump in/from DRAM (like greatfunky already said)
- removed some unused code (some more still here)

It's cleary the best of the bios with 16k page

I also started to port the 3.3c bios to WLA DX so it will be a open source bios 'soon' :)

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Post by greatfunky » Sat May 26, 2012 9:32 am

i'm glad to see that 3.3c bios is the best :D , i think that bios is the last of the 16k versions because i have also a 4.1-A smd and their serial numbers are close .

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KanedaFr
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Post by KanedaFr » Tue May 29, 2012 12:30 pm

There is something I don't understand....
On every bios, there is a vector table

Code: Select all

.org $0000
		jp	RESET
		jp	print_hexascii_byte
		jp	print_msg_at_HL
		jp	VDP_cls
		jp	init_VDP_and_character_set
		jp	loadCartInDRAM
		jp	handle_pc_command
How these interrup handler are called ?
RESET is called at startup, ok...but what about the others ?
I didn't find any rst XX on disassemby so I assume it's an hw interrupt call (strage for a "print_msg_at_HL"!)

from Charles's SMS tech doc,
The interrupting device can place a single or multi-byte opcode on the
data bus for the Z80 to fetch and execute when an interrupt occurs.
but, unless I missed something, the INT isn't connected on Genny so this can't happen...

Note all but RESET are in fact called from anywhere on the code and use a basic "ret" not "retn" so I suspect the vector table is invalid.
What do you think ?

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Re: Super Magic Drive research thread

Post by HardWareMan » Sun Jul 16, 2017 12:26 pm

This is normal practice. This table can be used by downloadable software. And these vectors will always be true, even if the system software is updated.

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