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Sega Master System Prototype M404 BIOS
Dumped by Omar Cornut (Bock) on 2004/10/01
http://www.smspower.org
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This is from a prototype Sega Master System that I acquired. This
model was sent to Sega of America at some point (undated). The BIOS
is on an EPROM, and is labelled:

    oekaki (in Japanese hiragana)
    M404

My uneducated guess is that "M404" stands for "Mark 4 version 04".
Mark 4 is the codename for the Master System. Version 04 may stand
for the BIOS version.

What the BIOS does is:

  - Display an animation (maybe better than final unit animation).
  - Copy a block of code to RAM at location $C100.
  - Try to detect a valid media on card, cartridge or expansion slot
    (in this order). If found, enable slot and jump to $0000 to
    execute.
  - Else, loop indefinitely.


The media detection code itself is very different from final units.
What it does for each port is:

  - Look for the "COPYRIGHT SEGA" string at location $7FE0 on media.
  - Look for the "COPYRIGHTSEGA" string at location $7FE0 on media.
  - Look for values C3 C8 00 01 at location $0038 (int vector) on
    media. This stands for a 'JP $00C8' instruction followed by a $01.

As a result, most retail Sega Master System games will not boot using
this prototype BIOS, as they do not contain either string. There is a
minimal chance that some games may contain the right byte sequence at
$0038.

Two games were found to contain this identification string:
  - Japanese version of Fantasy Zone (first SMS cartridge ever
    released)
  - Choplifter (first or second SMS cartridge ever developed)

I modified an original piece of software (Alex Kidd in Miracle World)
to include the required string, and it played well on the system.


For reference, retail Export SMS BIOSes look for a header starting
with "TMR SEGA" at location $7FF0. This header is described at:
    http://www.smspower.org/dev/sdsc/SDSCROMTag101.txt
Note that this DOES NOT apply to this prototype BIOS. The Japanese
SMS BIOS only looks for some non-sequential data, based on the fact
that early Japanese software did not have any header. So I cannot
conclude whether this prototype BIOS and the associated unit were
made before or after the release of the Japanese SMS.


There's no hidden game or other features included in this BIOS, as
far as I know (I've read most of the Z80 code). The code does not
access the PSG or controller ports.


-Omar Cornut
http://www.smspower.org