SVI738 upg. MSX-2 + 128kb V-Ram + PAL/NTSC + RGB

Rookie (29)

09-10-2012, 11:44

Hello guys,
I am in need of some advice here accordingly to an MSX.
The model is SVI738 express. When I boot it up it says it has 128kb vram, MSX Basic v2.1, Disk Basic v1.5.
So far so good, but it has more things than that. There is an RGB switch which will change/switch between colors and grayscale. I've came to the conclusion that is what's known as the SVI RGB mod.
Anyone know what it does more specifically?
It's attached to the MC1377(Color Television RGB to PAL/NTSC Encoder) on PIN 3, 4, 5.
Those pins are controlling the RGB, so this makes kind of sense. The SVI-RGB board must then take the RGB-out and just "fix" it so it's possible to connect it to an RGB monitor/SCART (that I've tried and it works).

Now, moreover we're coming to the other modification that is from what I've traced via schematics, datasheets and the SVI-Reference sheet(along analysis of the logic IC), would be somekind of 50/60Hz switch, since it's has a xtal onboard and it contains clock ICs and it's connected to the clockport.

Has anyone of you seen this modification before?
Also I wonder a bit about if it's possible to upgrade the Roms to 2.20 and a newer disk rom?

On top of this, I've tried to get my sunrise Compact Flash Card (CF-ATA-IDE), cart working, but for some odd reason I can't get the (damned) floppy/system to read the DOS2.20+FDISK tools. Is this frustrating or what? Yes it is

Lots of questions here but I hope to get some help.
I include some picture of the mods and stuff like that.

I also made a youtube-video about this machine. Keep in mind I made this one LONG time before I know what I know about the MSX today :)
http://www.youtube.com/watch?v=rSjvdV-eINE

Have a nice day,
Xiny6581

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Van bennyroger

Expert (74)

09-10-2012, 15:55

How much memory do you have? The SVI738 comes with 64kb ram and without a mapper dos 2.20 won't start because it needs at least 128k

Van Xiny6581

Rookie (29)

10-10-2012, 15:15

It has 128kb ram.

Van RetroTechie

Paragon (1563)

10-10-2012, 15:23

Can you post Xtal freqency and IC types in the 2nd pic? Might be a turbo circuit, for example CUC 6 MHz circuit. Xtal frequency might tell more...

Van Xiny6581

Rookie (29)

11-10-2012, 12:37

The Xtal is HCJ 6.0000000MHz
The IC types are 74LS04PC (Hex Inverters / Hex Inverters (with Open Collector Outputs))
/Xiny6581

Van RetroTechie

Paragon (1563)

11-10-2012, 14:32

Probably CUC's 6 MHz circuit then, as it was built using standard 74LSxx IC's. Not sure whether transistor + variable resistor is 'normal' part of that circuit though, might be a custom modification. (I should have, but can't find a schematic for that CUC circuit here)

Btw. 74LS04 is a regular inverter (6x), not with OC outputs.

Van bennyroger

Expert (74)

11-10-2012, 15:48

Xiny6581 wrote:

It has 128kb ram.

From your pictures I can only see 128k vram and 64k dram........

Van Xiny6581

Rookie (29)

11-10-2012, 15:52

Great. I did some reserach on the web and found this:
http://www.msxarchive.nl/pub/msx/mirrors/hanso/hwmodsetc/svi...
It looks kind of like the modification I have.
I am going to dump the ROMS (with my epromprogrammer) to see the exact version), then I might try to upgrade to DOS2.20.
I hope I can get the modicifation more stable and benchmark it to see what kind of speed it runs at.
/Xiny6581

Van mohai

Paladin (1007)

12-10-2012, 14:10

Hello,

what you have is a moded SVI 738.
As you can read in that document, it has:

- 6 Mhz turbo. Board stick to the cartdrige slot an switch in the side.
- 128 KB VRAM. Do not mistake with main RAM, as you have only 64 KB.
- MSX-2 ROMS. First chip is BIOS+BASIC, second is MSX-2 Extensions +DISKROM and third one is RS-232.
Wire on BIOS chip is for an extra address signal.
- Clockchip
- RGB Out. It can be switched off to get some kind of s-video and a special cable (IIRC).
- Double side diskdrive.

I have one moded to MSX-2 too, but i never got clock chip working.
Can you please post some pictures of that mod in yours?
You can find clockchip under diskdrive.

regards

Van Xiny6581

Rookie (29)

12-10-2012, 22:13

Mohai: It makes sense.
I've pulled out the eproms and read them with my epromprogrammer and yep I kind of had it sorted, but I wanted to see what was exactly in the eproms. The last chip was the most one I was interested in. So yep

If you look at the youtube video I posted, that will cover most of the modifications .But of course I can take more pics of them. I want to take a look under the diskdrive but last time I tried to lift it up, it struggled very much so I left it alone.
Also I've replaced the NiCa battery with a fresh one, just to be sure of no leakage.

Do you know if it's possible to add more main RAM? That would be pretty nice to have.
/Xiny6581

Van Xiny6581

Rookie (29)

13-10-2012, 10:32

Oh. I didn't know that until now. I thought it was about the same. But yep now I know
Thanks for pointing this out.
Now I just want to know how to add more dram.
/Xiny6581