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Van Grauw

Ascended (9181)

afbeelding van Grauw

22-06-2020, 15:05

On the VDP Ports wiki page it says:

Quote:

*Since MSX2+, the ports of CPU # 98 to # 9B have been standardized.

Do you have a source for this? Otherwise I would omit this claim.

Van gdx

Prophet (3571)

afbeelding van gdx

22-06-2020, 15:57

I read this announcement in a Japanese doc or technical magazine in the past but I don't know which one.

Grauw wrote:

Otherwise I would omit this claim.

It is not worth looking for the source since it is confirmed by Japanese programs which date from MSX2+. Many programmers no longer bothered to read the port numbers at addresses 0006h and 0007h after this ASCII announcement.

Van Grauw

Ascended (9181)

afbeelding van Grauw

22-06-2020, 16:08

Unless you show documented evidence I consider it an urban legend…

I’ve heard this claim in the past, even repeated it myself, but it’s always been heresay and I’ve never actually seen anything to back it up. So for a quality wiki, I would not propagate this myth without evidence that it’s fact. If this is true then you should be able to find it in technical documentation.

I’ve looked for it in the available manuals in the past (MSX Datapack, TurboR technical handbook), and I’ve never been able to find anything. I do recall reading about standardising the slot layout with the MSX2+ (see MSX turboR Technical Handbook section 2.1.6), but there was no word about the VDP ports.

Van gdx

Prophet (3571)

afbeelding van gdx

22-06-2020, 16:13

Japanese people like Gigamix or Okei know probably it, but whatever, even if they confirm or if I find the source, you probably wouldn’t still believe it.

Van Grauw

Ascended (9181)

afbeelding van Grauw

22-06-2020, 16:12

gdx wrote:

but whatever, even if they confirm or if I find the source, you probably wouldn’t still believe it.

I’m sorry what? What kind of attitude is that?

What have I done to you to deserve this kind of response?

Van gdx

Prophet (3571)

afbeelding van gdx

22-06-2020, 16:13

What i mean is me, I am sure and certain that it is not a myth since I saw the source of myself so I would not erase it.

Van Grauw

Ascended (9181)

afbeelding van Grauw

22-06-2020, 16:14

All I request is that you, or someone else, try to find it Smile. Because I don’t know what you read, what the context was, whether the translation or interpretation was correct.

Van gdx

Prophet (3571)

afbeelding van gdx

22-06-2020, 16:22

If you want, add a remark like "need official confirmation" but don't delete it.

Van mars2000you

Enlighted (5635)

afbeelding van mars2000you

22-06-2020, 17:21

According this Japanese page, it would be 'Since MSX Turbo R" instead of 'Since MSX2+":

http://www5d.biglobe.ne.jp/~hra/note/onechipmsx/research/v99...

"
port#0 が 98h でないような特殊な環境( MSX1 に MSX Adapter を接続して MSX2 にした環境など)では正常に動作しない。
そういう特殊な環境にも対応させる場合は、port#0 がどこに接続されているか MAIN-ROM 0006h, 0007h を読んで対応しなければならない。
0006h は IN用、0007h は OUT用の接続アドレスが記述してある。
特殊なシステムに対応するためには、MAIN-ROM の存在するスロットの番号もシステムワークを参照して調べるべきであり、とんでもなくめんどくさい構造になっている。
この辺を回避するために、MSXturboR規格 からはスロット構成が統一されているし、VDP のポートも決まっているので、turboR以降なら ポートを決め打ちで処理しても問題ないし、MSX2以上であってもたいていの場合問題ない(と思う)。"

what means:

"
It does not work properly in a special environment where port#0 is not 98h (such as an environment where MSX1 is connected to MSX Adapter to make MSX2).
To support such a special environment, you must read MAIN-ROM 0006h and 0007h to find out where port#0 is connected. 0006h describes the connection address for IN, and 0007h describes the connection address for OUT.
In order to support a special system, the slot number in which the MAIN-ROM exists should also be checked by referring to the system work, and it has a terribly troublesome structure.
In order to avoid this area, the slot configuration is standardized from the MSXturboR standard, and the port of VDP is also fixed, so if turboR or later, it does not matter if the port is processed by stubborness and if it is MSX2 or higher, in most cases (I think) there is no problem."

Van Grauw

Ascended (9181)

afbeelding van Grauw

22-06-2020, 17:34

Since the MSX turbo R Technical Handbook referenced some MSX Magazine articles I checked them out…

I checked the MSX2+ Technical Expedition articles in MSX Magazine issues 02-1989 and 03-1989, and the MSX turbo R Technical Analysis article in issue 11-1990. I also checked the MSX2+ special in MSX Magazine of December ’88. No word of standardised I/O ports at 98H.

Lastly I checked the other MSX magazine issues of 1989 and 1990, in particular articles in the “MSX2+ Technical Expedition” series. In issues 11-1989 and 12-1989 the topic is scan line interrupts. On page 173 it still says, and I quote:

“The address of the I/O port that connects the CPU and VDP is usually 98H to 9BH. However, as shown in table 1, it is determined by the contents of ROM addresses 6 and 7. This is because it is possible to add a VDP outside the MSX main unit. Note that the address of the I/O port may be different for writing and reading for the same port 0.

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