Bitmap multicolor mode of TMS

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Van ToriHino

Paladin (721)

afbeelding van ToriHino

21-07-2021, 17:29

On a real Turbo-R (V9958) you also get the full white area.

Van PingPong

Prophet (3756)

afbeelding van PingPong

21-07-2021, 21:50

it does appear that v9938 does not emulate TMS undocumented modes.
thx for the feedback
my idea was to try the OR8 and the OR16 combinations, but i seed that they are only for TMS...

Van Manuel

Ascended (18088)

afbeelding van Manuel

22-07-2021, 00:17

And as far as I know, openMSX also emulates them as such. But please comment if I'm wrong.

Van PingPong

Prophet (3756)

afbeelding van PingPong

22-07-2021, 01:04

openMSX does. but i think v9938 not. to confirm i need to use a stardard msx1 machine on openMSX but i do not have proper roms

Van gdx

Enlighted (4637)

afbeelding van gdx

22-07-2021, 10:15

Tested on MSX2 with v9938. I get a white screen.

Van Grauw

Ascended (10019)

afbeelding van Grauw

22-07-2021, 14:43

PingPong wrote:

my idea was to try the OR8 and the OR16 combinations, but i see that they are only for TMS...

Also note that a number of MSX1 computers have a Toshiba T6950 or Yamaha YM2220 VDP, and it is not guaranteed that they support these either. Especially the T6950 we know is quite different from the TMS9918 internally and does not behave the same in various undocumented cases.

Van PingPong

Prophet (3756)

afbeelding van PingPong

22-07-2021, 19:59

I explain better my idea. originally what i've tryed to achieve is a screen 2 mode, arranged on 40 columns (like screen 0), with the usual three band partition of screen 2 with sprite support.
So i apologize for the wrong title. and the wrong listing.

From wikipedia:

Quote:

Texas Instruments originally only documented the four modes listed above. However the bit that enables mode 2 is more interesting than initially let on. It is best described as a modifier bit for the other modes. Enabling it does three things:[3]

Expands the color table size.
Divides the screen horizontally into thirds.
Changes two address bits of the pattern and color tables into mask bits, which control if each third of the screen has its own pattern and color table or not.
With this in mind, three additional modes are possible. Note that although genuine TMS9918A chips support these modes, clones and emulators may not.

Mode 0 (Text) + Mode 2 (Graphic 2): Known as Bitmap Text Mode. This mode allows for two-color bitmap images, with no color table. This saves memory, at the expense of a slightly reduced horizontal resolution (text mode has a horizontal resolution of 240 pixels instead of 256 pixels like the graphic modes do).

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