Omega DIY 50 hz or 60 hz

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By Sukerbole

Supporter (8)

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30-01-2022, 16:17

Dear MSX Forum,

Some time ago I made an PC XT clone based on a design from Sergey Kiselev which was a fun project.
After some googling I found that Sergey also made an MSX design. I just bought the pcb’s from him.
I would like to know your opinion about which frequency would be ideal for me 50 or 60 hz.
I’m not an MSX expert so I’m not sure if it makes a lot of difference as I live in the netherlands the logical thing to do would be pal 50 hz.
Please let me know your expert opinion.

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By Manuel

Ascended (18853)

Manuel's picture

30-01-2022, 18:11

It only really matters for composite output and not for RGB output. I'm not sure whether the board has composite output and thus components that depend on the video standard.
The V9938 can switch 50/60Hz and the default is set in the BIOS you use.

By Sukerbole

Supporter (8)

Sukerbole's picture

30-01-2022, 19:36

Hello Manuel,

Thanks for the feedback.
Yes the Omega diy MSX has a composite out, audio, rgb, printer, casette and two joystick ports. (no floppy).
So I will then select the 50 hz option.
Just had a look at the videochip I bought. It is a Yamaha V9958. The V9938 is also supported however the V9958 was a bit cheaper on ebay so I bought that one. (On the mb you can select the ic) I assume this chip is also 50/60 compatible. So the default is set in the bios. Does it matter much 50/60 hz or is it comparible with the Sega Megadrive were most games play much better in 60 hz.
I’m not sure if I will play much games because probably the building and getting it to work is the best part Smile

By meits

Scribe (6509)

meits's picture

30-01-2022, 23:38

The v9958 can do 50Hz as well indeed. They were (are still) used to upgrade MSX2 computers to MSX2+. Only Japanese computers (MSX2+ and MSX turbo R) have been released with this chip on board.

By Manuel

Ascended (18853)

Manuel's picture

30-01-2022, 23:51

As you can change the output frequency in software, you can set it to whatever you want. Usually it's a good idea to put it in the setting that matches to what the game developers were using. With the RGB output and a monitor that can handle both (like the typical good CRT from the 80's), you'll be completely good to go.

By Sukerbole

Supporter (8)

Sukerbole's picture

31-01-2022, 11:24

Thanks for clarifying!!

By jdgabbard

Resident (42)

jdgabbard's picture

16-02-2022, 17:50

Sukerbole wrote:

Dear MSX Forum,

Some time ago I made an PC XT clone based on a design from Sergey Kiselev which was a fun project.
After some googling I found that Sergey also made an MSX design. I just bought the pcb’s from him.
I would like to know your opinion about which frequency would be ideal for me 50 or 60 hz.
I’m not an MSX expert so I’m not sure if it makes a lot of difference as I live in the netherlands the logical thing to do would be pal 50 hz.
Please let me know your expert opinion.

You might closely examine the 9958 you bought from eBay. I recently did this, and what I received was actually a 9938 that had been sanded and relabeled.

By Sukerbole

Supporter (8)

Sukerbole's picture

22-03-2022, 23:52

So I completed most of the pcb.
Cbios seems to work.
When trying Msx 2 and 2 plus bios however the colours (red background instead of blue) are wrong.
Also the msx boot logo is not blue but purple with red.
Could this be bad vram?
Also there is some additionele text in basic.
Under copyright Microsoft it says “””2”
Even if I cls this ””””2” is stil displayed on top

By Grauw

Ascended (10604)

Grauw's picture

23-03-2022, 02:33

Sukerbole wrote:

When trying Msx 2 and 2 plus bios however the colours (red background instead of blue) are wrong.
Also the msx boot logo is not blue but purple with red.
Could this be bad vram?
Also there is some additionele text in basic.
Under copyright Microsoft it says “””2”
Even if I cls this ””””2” is stil displayed on top

Changing the boot logo colours etc is an MSX2 feature. VRAM is fine. Maybe an RTC problem, but it could also just be uninitialized.

See:
https://www.msx.org/wiki/SET_TITLE (boot logo)
https://www.msx.org/wiki/SET_PROMPT (“””2” prompt instead of Ok)
https://www.msx.org/wiki/SET_SCREEN (store default colour after COLOR 15,4,4)

Bas made a great video about it: https://youtu.be/BGfb1sJ3MQw

By sdsnatcher73

Prophet (3382)

sdsnatcher73's picture

23-03-2022, 02:31

MSX2 has a RTC clock chip that also keeps certain settings, possibly this is not working well in your build. The “”””2” should normally be the Ok prompt. You can reset it by command SET PROMPT “Ok”. The boot colors are similarly stored in the RTC clock chip and can be reset by SET TITLE “”,1

If these changes do not persist after power cycle check the clock chip.

By Sukerbole

Supporter (8)

Sukerbole's picture

23-03-2022, 08:03

Thanks for the tips.
Without the rtc chip the system does not seem to boot.
Just tried set prompt. I can indeed change the prompt however the text is messed up and not stable. For instance typing set prompt “hello” could display iello or -ello or somtimes hello (random). I also don’t see the bytes free message in basic. Typing the cls command also could mess up the text at the bottom (color auto….).
Typing 10 print “hello world” 20 goto 10 and running it also shows very inconsistent printing of hello world. It is all over the place. Every time different characters are wrong.
The rom I’m currently using has cbios in the second part of the rom with the Konami game Knightmare. That all seems to work OK. I can play the game.
Because of the inconsistent display problem I was thinking that part of the vram was maybe bad but maybe the rtc could also cause this? Both the vram and ricoh chip are from eBay. But even with a bad rtc should it properly display print hello world and the bytes free message at basic startup?

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