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By ren

Paragon (1797)

ren's picture

12-05-2021, 14:23

Manuel wrote:

Do you get the same on a plain NMS 8250 then?

No issues there. Using original 8250 VDP config inside the boosted config solves the issues. Using the V9958 config inside the original 8250 config gives same issues.

And using the WSX MSX2+ roms in the boosted MSX2 config works (no issues).

So to me (far from versed) looks like a bios <> non-original/unexpected vdp thing?

A real world MSX2 to 2+ upgrade entails replacing the main- & sub roms right?

So it's expected sw fails on this? Perhaps it should simply use the original V9938, or otherwise come with a big fat warning? Big smile

(Another option could be a config with hacked English/PAL MSX2+ roms, but I just read (skimmed) in gdx's thread those are of questionable quality?) (Not sure, perhaps he was talking about another kind of patched roms.)

By Manuel

Ascended (17882)

Manuel's picture

12-05-2021, 15:21

Thanks for diving in! I wouldn't expect problems with replacing vdp without bios... Perhaps more knowledgeable people can comment on this?

By Grauw

Ascended (9830)

Grauw's picture

12-05-2021, 15:28

In the end it’s a software issue I guess, detecting VDP ID and then assuming the BIOS is there to match.

However I would use the V9938 instead of the V9958. The VDP is the core characteristic of the MSX1, 2 and 2+ generations, so a “boosted” MSX2 with V9958 is a bit strange to me, if people want that VDP they should select the boosted MSX2+. Additionally, 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.

By ren

Paragon (1797)

ren's picture

12-05-2021, 17:18

Ah, of course, V9958 should be 100% V9938 (instruction wise) + extra stuff.. If it's fully(?) bw compatible that would explain most sw working fine, unless indeed some false(?) (the wiki mentions V9938 specifically as part of the MSX2 standard definition)* assumptions via (incomplete) detection are made :)

E.g. unpatched Space Manbow runs fine, using V9958 scrolling behavior (no shaky borders).

Though I suppose when software uses some VDP BIOS routines, the V9958 will look like it's a V9938 (and act accordingly) right?

I get V9958 would fit in a boosted machine (giving MSX2+ features to a still European/PAL machine), but as outlined above, is issue prone :) So as/by default I agree it's prolly better to just use the V9938.


* Although real world MSX2 + V9958 machines exist as well. (Do these actually violate the MSX2 SD?)

By Grauw

Ascended (9830)

Grauw's picture

12-05-2021, 18:11

I don’t know what SD means but yes real MSX2 machines with a V9958 exist (also MSX1 machines with V9938) and are perfectly standards compliant, and there are also people who have modified their MSX2 with a V9958 without replacing the BIOS, in fact that is the case for my NMS 8245. So this hardware combination exists in the wild and this software will probably also not run properly on them.

By ren

Paragon (1797)

ren's picture

12-05-2021, 19:32

'standard definition', as e.g. used here in the wiki.
I'm not sure how accurate or official the criteria mentioned in that list are?

So for one, it explicitly states 'V9938', that would make any 'MSX2' using something else non-standard right.

Nothing wrong per se with non-standard, but then we can't blame sw running incorrectly on these machines right (even when they could run properly with e.g. better detection algorithms)?

By Manuel

Ascended (17882)

Manuel's picture

12-05-2021, 20:45

V9938 or compatible, I guess. And V9958 is compatible.

By Grauw

Ascended (9830)

Grauw's picture

13-05-2021, 00:44

The wiki is just people writing down whatever they want Wink.

By ren

Paragon (1797)

ren's picture

13-05-2021, 09:17

Manuel wrote:

V9938 or compatible, I guess. And V9958 is compatible.

I suppose...

There must be an official spec / 'MSX(2) Standard' document?

Grauw wrote:

The wiki is just people writing down whatever they want Wink.

Only to some extent I suppose Wink

By Manuel

Ascended (17882)

Manuel's picture

13-05-2021, 10:55

The best reference I can think of is probably the MSX2 Technical Databook.

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