To get into the game it looks in its start-up code for the address of an interrupt hook: first H.TIMI, the one of Konami's six MSX2 cartridges, then H.KEYI, the MSX one (p00:588C). Game Master 1 only looked for the second. Checked with the ROMs: the six MSX2 ones write to H.TIMI and none to H.KEYI.
The signature table (p00:44BE) is Game Master 1's plus five for Vampire Killer and one for Hinotori: 68 for 30 games.
If the BIOS character set is not the Japanese one, the cartridge forgets it is on an MSX2 and shows the MSX title sequence without the title (p09:8024).
To clear the VRAM it uses BIGFIL (0x016B) on MSX too, where that BIOS entry does not exist (on the C-BIOS it is zeros up to 0x0200): the VRAM is not fully cleared. It does not show because what is left falls on characters the screen does not use. Checked against openMSX: on the SELF menu 8,322 bytes of the tables differ and not one dot on the screen.
The Tennis and Hockey engine has three music tracks and two effect tracks; an effect takes PSG voice C or B if its priority is not lower than the music's, and gives it back when it ends (p08:A291).
From 40 the next point wins the game, whoever reaches it first (p07:9290), and the set ends at 6 games with no need for a two-game lead.
On MSX2 the colours of the curves rise a little each day of the animation until they are yellow, cyan and magenta (p06:A2B7).
The "GAME MASTER II" title on non-Japanese machines reuses characters between words (p09:8D99). In the middle column of the M of MASTER, at the bottom (p09:8DD5), it puts character 0x21, which is the corner of the G, where the M of GAME has 0x26: that is why that M comes out with an odd piece. openMSX draws it the same way.