SW101 switch on Philips NMS-8250 motherboard

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By dhau

Paragon (1557)

dhau's picture

09-05-2004, 05:05

Hi folks,

I need even more help with my MSX hardware. I recently opened my 8250 what I bought from Bas before I got TurboR GT from SST. I didn't expected much, but then I looked inside, I must say I was impressed a lot. This thing is built to survive 10G take off to space or a direct nuclear bomb hit! Amazing: many layers of think steel, a lot of holding screws on each board, no soldered wires between the boards, all uses flexible connectors. I must say I respect the design very much.

I was planning to investigate the posibility of moving 8250 guts into a nice clean old PC AT case, adding Padial's Evo4 slot expander with lots of extensions (SCC+, MSX-Audio 256KB, FM-PAC, GFX9000, Sunrise IDE, 4MB RAM and 512 flash ASCII 8kb).

But after seeing how beautifully it's designed inside, I decided not to do the move. At least not with 8250. I still probably will sacrifice a Sony F1-XD (MSX-2) to build a nice souped up MSX in PC case.

Anyway, back to the point: there is a fairly big switch on 8255 board. It's marked SW101. If you know what it does, please let me know.

I really hope it switches the video-mode from PAL to NTSC, but don't have a chance to check it out at this time (can't find my 110v -> 220v transformer)

Thank you in advance,

Adrian

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By [D-Tail]

Ascended (8233)

[D-Tail]'s picture

09-05-2004, 09:55

The fact that MSX is still better than those nought wintel bricks is also due to their solid construction Smile

The SW101 is a white-coloured switch, if I'm not mistaken. I don't know exactly what it does, but if you depress it, your MSX won't startup anymore. If you then release it, it will boot again like normal.

It anyway doesn't switch the video mode from PAL to NTSC, because the whole NMS-series is European only, therefore, PAL. So yes, if you want to work in 60Hz mode, you should try typing VDP(10)=0 Big smile

So anyway, if your 8250 doesn't boot anymore, try releasing that switch Wink

By Manuel

Ascended (15763)

Manuel's picture

09-05-2004, 14:36

The switch is an old subject. I guess I should put it in the FAQ... It's for the Service Test Cartridge. The 8250 will boot the STC ROMs instead of the normal MSX ROMs when it is switched.

By mth

Champion (484)

mth's picture

11-05-2004, 00:51

About PAL and NTSC: the V9938 can do both, which mode it uses is determined by a register: R#9, or VDP(10) in BASIC terminology. You could convert your 8250 to NTSC by changing the BIOS. Either hex-edit the 8250 BIOS or try to find a Japanese machine with hardware similar enough to the 8250 (maybe one of the Sanyo machines; Sanyo built the 8250 after all). You could test such a BIOS in an emulator and if it works, you can load it into an EPROM and put it in your 8250.

By Sonic_aka_T

Enlighted (4130)

Sonic_aka_T's picture

11-05-2004, 01:32

Actually, you'd also need to change a whole lot of hardware... All the VDP can do is switch to 60HZ. It has no PAL/NTSC option or anything that'll change the signal that comes out the computer. The entire video-encoding to composite video or antenna is done by separate hardware that would need to be replaced. (Either for the composite or the RF connector)

By anonymous

incognito ergo sum (109)

anonymous's picture

11-05-2004, 01:39

Actually the VDP also changes the resolution.
The only thing it doesn't change to NTSC is the color information, as in most MSX models the VDP only outputs RGB and composite video is encoded seperately.
It does mean you can use the VDP(10)=0 (or rather VDP(10)=VDP(10)AND253) trick to output images to your NTSC-only monitor/TV using the composite output, but they will be in black&white.

By mth

Champion (484)

mth's picture

11-05-2004, 10:59

Ah, I forgot about the colour encoding. I always use RGB connectors here, so there is no encoding, but for some reason video equipment in the USA/Canada seems to support S-Video but not RGB.

Would it help to write different values to the colour burst registers, or is that something else entirely?

By [D-Tail]

Ascended (8233)

[D-Tail]'s picture

11-05-2004, 11:26

What are those colour burst registers for anyway? Never understood their meaning...

By anonymous

incognito ergo sum (109)

anonymous's picture

11-05-2004, 14:00

The colorburst registers are used with the composite video output of the VDP. But as I said, most MSX machines use the RGB output and encode the composite video seperately.
I believe there are some MSX's that do use the VDP composite output, but I don't know what kind of results can be achieved by reprogramming the colorburst registers.

By mth

Champion (484)

mth's picture

12-05-2004, 01:57

There is a demo from Chile made in the mid-90's which uses the colour burst registers for an effect. I've never been able to see it, but apparently its programmer had an MSX which does use the colour burst registers.

By dhau

Paragon (1557)

dhau's picture

12-05-2004, 23:13

Strangely enough, then I connected my PAL 8250 to NTSC only TV, I can see all the right colors, but picture is out of sync... So I don't think there are any color problems if you use RGB, S-Video (separate chroma and lumina) or Composite. I think there are problems with RF out, but I'm not an idiot to use RF Smile

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