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By ren

Paragon (1797)

ren's picture

14-05-2021, 13:10

Cheers, MSX2 Technical Handbook (courtesy of Konamiman).

It just mentions V9938. Though if variants or clones would exist at that time, it might have said 'V9938 or equivalent/compatible' :)

By Grauw

Ascended (9824)

Grauw's picture

14-05-2021, 16:04

This is kind of what I mean with “it’s just people writing down whatever they want”; depending on your angle on how you read that specific document (which is a transcription of a translation btw), you could either make a hard conclusion that it doesn’t say “or equivalent” so equivalents are not standard, or that they weren’t aware of alternatives yet and since the V9958 is compatible it must be standards compliant, or that it’s just not really specified in enough detail and we can’t make any hard statements about it at all.

Things are up for interpretation, and if you read the wiki you’re reading someone’s interpretation. At least if you read the officially published original documents you are only subject to your own interpretation (and I guess the author’s and translator’s).

That isn’t to say the wiki is not a great resource, but you were asking how “accurate or official” the info there is, and the answer it’s certainly not official, and the accuracy varies. When you find an inaccuracy, since it’s a wiki you are free to modify because accuracy is the aim. Of course it could turn out that you were wrong, which brings us back to “people writing down whatever they want” Wink.

Another good source of information is the openMSX source code, since a lot of the implementation there is backed up by thorough research and testing, and findings and assumptions are generally commented in the source code. It includes a lot of the details that aren’t mentioned by official documents. But at the same time I also regularly find inaccuracies compared to real hardware, even in an emulator as mature as openMSX.

Lastly, though official documentation is my preferred source of information, even that has inaccuracies and errors. For instance I can point out several issues with the official documentation for the Z80 CPU, the V9938 and MSX-DOS2.

By ren

Paragon (1797)

ren's picture

24-05-2021, 02:44

Sorry, went silent, but I get you (and (personally) I understand the nature of a wiki Smile)

Grauw wrote:

which is a transcription of a translation

Don't you mean the other way around?

Something interesting I just read in the Gradius 2 patch news topic:

sd_snatcher wrote:

Feature request: if you have an MSX2 with a V9958, it doesn't do smooth scroll, please detect the VDP instead of relying on address 0x2D.

Unfortunately this is not possible, because those machines don't have the VDP wait-signal circuitry, which is mandatory for a MSX2+ and is required by the smooth scroll routines because I'm using the high speed VRAM transfer by enabling the WTE bit of the register #25.

By gdx

Enlighted (4377)

gdx's picture

24-05-2021, 03:25

I don't know any document that is 100% reliable. There are several errors and interpretations in all documents even in ASCII Datapacks.


the colours of the V9938 (9-bit RGB DAC) are different from the V9958 (15-bit RGB DAC), so the V9938 also gives a more accurate colour reproduction for an MSX2.

YJK modes require mode bits to display the numerous colors. It doesn't change anything for the other modes.

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