mysterious switches

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By msxrestarter

Master (224)

msxrestarter's picture

03-11-2005, 20:30

Who can help me with the following :

I've got me a NMS8280 with a lot of internal modifications but I don't know them all.

The first I'm sure of is a memory expansion to 1MB, as you can see on the starupscreen below.

The second is the power supply with coolfan.

The others I'm not sure of. As you can see on the picture below there are 3 switches on the frontpanel.

The one on the left is a 7Mhz on/off switch I gess, because when I switch this on, some games go faster and the sound is disturbed.

The other two I don't know.

There also tampered with the video output, anybody knows this ?

Maybe one of those undefined switches has something to do with it ?

Then there's still one undefined switch, maybe DOS 2.20 ?
Or if I'm really lucky converted to MSX2+ ?
How can I check this ?

Seems like this 8280 belonged to a real MSX diehard, maybe anyone recognizes his old computer and can tell me more about it !;)

I think I got me a really nice MSX2 this time !
I'm pretty happy with it !LOL!

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By Mirg

Expert (88)

Mirg's picture

03-11-2005, 20:43

An MSX2+ boots up different compared to an MSX2.
On the MSX2, the logo block scrolls into view from bottom to top.
An MSX2+ bootup has the logo split up in two parts, one scrolling
into view from the left, the other from the right. When they
overlay, the logo's formed.

So, if you flip a switch, boot up and see the logo coming from
the sides, you found the 2+ switch. Smile

(I entered a lot in the post to keep it readable.)

By HansO

Paladin (672)

HansO's picture

03-11-2005, 20:51

It sure is a very nice MSX!
The video modification is made by the Tilburg MSX club, allowing s-video inout and output and correction of pure white. I ahve that too and used that a lot when the NMS8280 was part of my video editing workbench.

The two misterious switches indeed can be for quite popular NMS8280 modifications:

- switch between MSX2 and MSX2+ roms. Easy to check if screen 12 can be selected (see the MSX2+ basic extensions for that or download a 2+ game. It shows after bootup also.
- switch on/off DOS 2.20 internally (do the wires go to eproms?)
- switch between s-video and composite video (since you have that inside), wires go the back?
- whatever the owner felt was necessary Smile

The switches look familiar btw, seen that kind used a lot by modders.

By legacy

Hero (570)

legacy's picture

03-11-2005, 20:56

To check if it is an 2+ give in basic only "screen 12", if you get no error, then it must be a 2+.
Hm, a bit to late.Wink

By msxrestarter

Master (224)

msxrestarter's picture

03-11-2005, 21:11

Damned, no MSX2+.Crying
Screen 12 gives a "Illegal Function call" and startup screen doesn't change.

When I use the switch in the middle a different Disk Basic version is displayed. It changes between Disk Basic 1.1 and 2.03
Does this has something to do with dos 2.20 maybe ?

The switch on the right seems to be wired to the extra video output print.
Hans, how can I check the switch between s-video and composite video ? (Don't even know the difference between both formats)

By Manuel

Ascended (18958)

Manuel's picture

03-11-2005, 21:16

Yep, the middle switch is for DOS 2 Smile

The right siwtch is probably indeed to switch between S-video and composite. S-video is a lot better in quality.

By msxrestarter

Master (224)

msxrestarter's picture

03-11-2005, 21:29

Another mystery solved then !Smile

Left switch : 7Mhz on/off
middle switch : Dos 2 on/off
right switch : s-video on/off (just have to check this later)

Just another question : how is the 1024Kbytes message on the startup screen altered ?

I also have a NMS8245 with 256Kb mapper but the startup screen displays the normal 128Kb user ram.

By msd

Paragon (1483)

msd's picture

03-11-2005, 21:38

A switch for disabling dos2... haha they probably didn't know there is a key combination to disable it during boot.. graph+code

By turbor

Champion (501)

turbor's picture

03-11-2005, 21:38

Just another question : how is the 1024Kbytes message on the startup screen altered ?

On most MSX2 machines (all that I know of), the amount is simply a text burned into the roms.
So if you want to alter those texts, you'll have to replace the rom with some newly burned (E)PROM

IIRC MSX 2+ and Turbor-R machines are the ones that actually count the memory before displaying the number.

By msxrestarter

Master (224)

msxrestarter's picture

03-11-2005, 21:53

On ebay Repairbas sometimes mentiones a 'memory counter', maybe this does the trick.Question

By AuroraMSX

Paragon (1902)

AuroraMSX's picture

03-11-2005, 22:35

IIRC, some upgraders (probably including RepairBas) upgraded a lot of MSX2's with a modded ROM that indeed actually counts the available RAM. You probably have such an upgrade.
Apart from that, it could be that your MSX2 is only half upgraded to MSX2+ status: only the VDP upgrade, not the belonging ROM. Check the text on the VDP, if it isn't hidden underneath a large cooling plate Smile If it says V9958, you're in luck.

A '80 takes a lot of power, and with all those mods and etxra's it can get pretty hot: that's what the fan is for, I suppose.

BTW, did you actually check the functionality of the switches? Judging from the texts above, it seems that you're assuming their functions by what other people tell you. My '80 has 2 switches: one for 7MHz (as mentioned by others) and one for KUN-Basic.

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