Omega MSX as a 2+ with PAL

Expert (72)

27-03-2023, 13:17

Hi,

I'm sourcing the latest parts for my Omega MSX build. I found a V9958 so I want to turn it into an MSX2+. Not until I ran the script to generate the ROM file I found there is no such thing as an PAL MSX2+, right?

So my options are:

1. Just flash it as an MSX2 and use as a pure PAL MSX2 machine. Will this work? Is the V9958 100% backward compatible with V9938?
2. Flash it as an MSX2+ and user as an NTSC MSX2+ machine.
3. Some combination where I flash the basic bios and msx2sub roms of an MSX2 and the kanji and msx2psub from an MSX2+. What do I have then?

Any suggestions?

By Grauw

Ascended (10768)

27-03-2023, 15:13

Yes the V9958 is mostly compatible, bar some small pinout differences and minor features that were removed (mouse or light pen support or something like that, which MSX doesn't use). It can generate 50 Hz signals.

But I would go for option 2. 60Hz is generally superior in my book anyway, looks better on a CRT and more compatible with modern displays as well when connected through an OSSC or the likes.

By user888

Expert (72)

27-03-2023, 16:11

Thank you for the reply. Then I need to do some desoldering I guess. Do games detect 50 vs 60Hz or do I have to source other versions of my game collection?

By Briqunullus

Hero (665)

27-03-2023, 16:37

Nowadays the frequency is more or less a personal preference. In openMSX I run my machines (including MSX2+ and MSX turbo r) at 50 Hz, because that's what I'm used to. And it may make some games just a little bit easier.

As for the roms, you can assemble your own from msxsyssrc. In base300/msx.inc you can set your preferred country. This will set things like interrupt frequency, character set and basic version. In here 'USA' is the same as 'International', except at 60 Hz.

You may also have to adjust your slot configuration. I forgot the source file where that's stored. MSX2+ has the standard bios and basic roms, a subrom just like MSX2 and on top of that an optrom for the boot screen.

By Grauw

Ascended (10768)

27-03-2023, 17:04

user888 wrote:

Do games detect 50 vs 60Hz or do I have to source other versions of my game collection?

Generally it just works.

By Manuel

Ascended (19462)

28-03-2023, 00:20

The VDP can generate either 50 or 60 Hz output. It's software switchable, so there is nothing to detect. The only thing to consider is whether your display can handle it. When using old CRT's like I do, either is fine. And some game launchers let you decide before running.

By Dubbylabby

Resident (51)

28-03-2023, 01:23

https://msxmakers.design.blog/2022/09/14/todo-el-mundo-a-la-...

Maybe this can be helpful.

By user888

Expert (72)

28-03-2023, 07:48

Thanks everybody!

By user888

Expert (72)

28-03-2023, 07:52

I first have another thing to solve. I found that there is a short between GND and 5V! Luckily did not power it on. I now removed all ICs and now got 255 Ohm between GND and power. Not sure of that’s a normal value or not? (I’m more of a software guy)

By user888

Expert (72)

28-03-2023, 18:10

I found the issue for the short: a bad 74F245 IC caused it.

For a reference for other or future me: the board without IC's inserted, at 5V, draws 0.01A. The resistance between GND and 5V is then 255 Ohm.
With all ICs except the V9938 or 9953 (Ur), the VRAM, the 74HCT273 ICs (U8-11) and U43, it draws 0.62A. The resistance between GND and 5V is 253 Ohm. That is with a Microchip AY-3-8910A. With an Yamaha YM2149F the resistance drops to 156 Ohm. Power draw is the same.

(all with no keyboard attached)