Super Magic Drive research thread
Posted: Fri Dec 18, 2009 6:53 am
In a quest to get a working MS-DOS setup for my SMD800, I came across a few interesting things, and a need for a tool that I cannot find.
First of all, does anyone have a copy of Charles MacDonald's SMDUTIL? The link on his website is 404, and I can not find it anywhere (have done about two solid hours of Google scouring). I need it to dump my unit's BIOS, which reports onscreen to be v3.3 from 1992, and I have not seen any dumps of this version yet. I'd especially like to look inside it for an internal build date.
While searching for any information or tools, I came across five other BIOS dumps (although one isn't technically a "dump", more on this later):
* v3, 1991, available on the Sonic Retro wiki, internal date 8/17/91
* v3.1, 1991, available as part of "mdutils.zip" found here (see below), internal date 11/4/91
* v3.1g, 1992, available on the Sonic Retro wiki, no internal date
* v4.1a, 1993, available on the Sonic Retro wiki, "93-12-07" (ambiguous M/D ordering but based on v3 I will call it Dec 7, 1993)
* Magic Drive Plus BIOS, 1993, no internal date, no reference to either JSI or FFE, also includes anti-piracy message, available here
The 11/4/91 v3.1 version is quite interesting, as rather than being just a regular dump, it's a file of length $4200 (16896). In this file, it looks like the actual ROM begins at offset $1E00, and mirrors at $3E00 until the end of the file ($41FF). Within mdutils.zip, there is a "README!.MD" file which describes this file:
This seems to be pointing towards the "DOS can be updated by disk (ala Kickstart image files)" feature listed on the Retro wiki. My question is, has anyone ever found any other such upgrade files, and also has anyone ever taken a look to find out exactly how this type of upgrade works, such that one could upgrade their own unit to one of the other BIOS dumps available? I'd try merely replacing the 8K of data at $1E00 but I don't want to take a chance at bricking my unit. I don't have IDA installed right now so I can't check to see if there is any 68k code in there that would trigger the upgrade process once the data has been loaded into DRAM. It almost looks like there might be a speck of 68k in there at $0200, but I don't know enough about either the Z80 or the SMD's internal workings to make an educated guess.
First of all, does anyone have a copy of Charles MacDonald's SMDUTIL? The link on his website is 404, and I can not find it anywhere (have done about two solid hours of Google scouring). I need it to dump my unit's BIOS, which reports onscreen to be v3.3 from 1992, and I have not seen any dumps of this version yet. I'd especially like to look inside it for an internal build date.
While searching for any information or tools, I came across five other BIOS dumps (although one isn't technically a "dump", more on this later):
* v3, 1991, available on the Sonic Retro wiki, internal date 8/17/91
* v3.1, 1991, available as part of "mdutils.zip" found here (see below), internal date 11/4/91
* v3.1g, 1992, available on the Sonic Retro wiki, no internal date
* v4.1a, 1993, available on the Sonic Retro wiki, "93-12-07" (ambiguous M/D ordering but based on v3 I will call it Dec 7, 1993)
* Magic Drive Plus BIOS, 1993, no internal date, no reference to either JSI or FFE, also includes anti-piracy message, available here
The 11/4/91 v3.1 version is quite interesting, as rather than being just a regular dump, it's a file of length $4200 (16896). In this file, it looks like the actual ROM begins at offset $1E00, and mirrors at $3E00 until the end of the file ($41FF). Within mdutils.zip, there is a "README!.MD" file which describes this file:
Code: Select all
MDOS31.PGM
==========
LOADS ON MEGADRIVE INSTEAD OF GAME
LATEST DOS 3.1, FULL VERSION.
ALLOWS YOU TO LOAD AND SAVE FILES TO RAM (IE. LOAD A FILE BUT *NOT RUN*, THEN
SAVE TO ANOTHER DISK)