Undocumented Mode 1 + 2 : Poll/Discussion | MSX Resource Center (Page 3/4)

Enlighted (6932)

22-04-2019, 12:32

dvik wrote:

I read the karoshi topic and my Spanish is not so good but if I understand correctly the mirroring does not work at all on some early Sony machines, HB-20P for example. On these machines it sounds like only the top 1/3 of the screen will be shown correctly. But it sounds like its not a problem on all HB-20P machines.

I'm also very interested to hear more about question a. Would be great to know the answer to these more specific questions (same as yours ARTRAG but more explicit):

1. Does PCT mirroring cause sprite mirroring side effects?
2. Does PGT mirroring cause sprite mirroring side effects?
3. Does PCT+PGT mirroring cause sprite mirroring side effects?

Sprite mirroring is strictly related to PGT mirroring.
Mirroring color definitions does not cause any problem.
Only sprite planes 8 and upper are affected, so if you use only planes 0-7 you can mirror tile definitions without problems.
I know it is a bit late to answer, but better late than nothing ;-)

Par thegeps

Paragon (1175)

23-04-2019, 00:44

Yep, but mirroring doesn't work on all machines... So I think it's pretty useless

Par ARTRAG

Enlighted (6932)

23-04-2019, 01:01

Only a few early models with the old T6950
provided you make clear on the box,I wouldn't care

Par sd_snatcher

Prophet (3645)

23-04-2019, 02:17

jltursan wrote:

The machines that have been reported as "weird" (all of them seems to have the Toshiba VDP) are:
Toshiba HX-10
Toshiba HX-20
Sony HB-10P

Also known to be present on:

Hitachi MB-H50
Sony HB-20P (very popular in Spain)
Toshiba HX-30
Toshiba HX-31
Toshiba HX-32
Casio MX-15
Sakhr AX-230
Sony HB-501P
Sanyo MPC-200

This is not an exhaustive list. There might be others.

Par rderooy

Paladin (686)

23-04-2019, 08:18

Exhaustive list :-)
https://www.msx.org/wiki/Toshiba_T6950

The page could probably use a more detailed description of the problem.

Par ARTRAG

Enlighted (6932)

23-04-2019, 08:59

On Sony HB-20P the problem has been fixed in later revisions
Uridium has been reported to work on that machine

Par ARTRAG

Enlighted (6932)

23-04-2019, 11:34

Actually the wiki page should also mention that the hybrid mode is documented by TI
From Wikipedia:
commonly referred to as half-bitmap mode. Texas Instruments actually documented this "undocumented" screen mode in their manual titled "Video Display Processors Programmers Guide SPPU004". In section 8.4.2, Playing Games with VRAM Addressing, they discuss how this mode combines the memory savings of mode 1 with the color detail of mode 2. However, as they go on to say this mode limits the number of sprites that can be displayed to 8 instead of 32. Therefore, the term "undocumented" used to describe this mode is actually a misnomer. However, because this manual was not widely known, this mode is generally considered to be one of the undocumented modes.

Par ARTRAG

Enlighted (6932)

23-04-2019, 13:30

rderooy wrote:

Exhaustive list :-)
https://www.msx.org/wiki/Toshiba_T6950

The page could probably use a more detailed description of the problem.

Yes, only the T6950 is buggy and the Sony HB 20P is reported to have T6950A that supports mirroring

Par thegeps

Paragon (1175)

23-04-2019, 20:52

Yes, I'd like to use color mirroring too (my scrolling routine would be faster if I use it). But if my (future, I hope) game, when finished, will have a good result on MSXdev and someone will want to produce a collector's cartridge, it will be unfair if the game cannot work in some real hardware...
I know that with emulators you can play all the games in all kind of machines, but I think that a real cartridge in a real hardware is something special...
If results keep to be as good as are now I think I won't support mirroring (but I respect your point of view too, I know you want to squeeze all msx power; the standard is a good thing and an obstacle at the same time)

Par jltursan

Prophet (2619)

23-04-2019, 21:05

Too bad for the machines with a T6950 built-in, seems that it can't be replaced with a TMS chip as they have huge differences in the pinout and don't seem compatible even with an adapter (without additional circuitry I mean)