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

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Van Xiny6581

Rookie (29)

afbeelding van Xiny6581

13-10-2012, 10:36

bennyroger wrote:

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

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

Van Xiny6581

Rookie (29)

afbeelding van Xiny6581

16-10-2012, 21:14

Okay so here we go. I finally got some time to unscrew the floppy, to take a look what's there.
Here's the pic Smile

Best regards,
Xiny6581 ._,

Van mohai

Paladin (967)

afbeelding van mohai

16-10-2012, 23:04

Thanks for the picture.

To add more RAM, you have to replace existing RAM chips with 41256 ones. So, you will have 256 KB instead of 64.
4164 and 41256 are pin compatible.
Then add a mapper circuit to manage extra memory banks and an extra 74LS157.
You will have to cut some traces also.
I never did this mod, but it seems that it is not difficult.
I never found any document describing how to do that. I just figure it out.
If you have technical sheet for this model, you can figure out what modifications are needed.

regards

Van Xiny6581

Rookie (29)

afbeelding van Xiny6581

17-10-2012, 11:48

mohai:
Thanks for the great information. I've been surfing around on the net to find information about somekind of a mapper for the SVI 738, but yep just like in your case no documents describing how to do it. So I guess the brain has to work and well just "trial and error", so to speak.
I have a technical sheet for this model but I am too novice to know how to make the actual modification.
Perhaps I have to ask around for safe advice, which is proven to be working and do a nicely work.
It would be a shame to manipulate the MSX so it won't work at all, right? Wink
Greetings,
Xiny6581 Big smile

Van mtn

Champion (265)

afbeelding van mtn

26-05-2016, 20:04

Hey Xiny6581, former fellow c-64 scene groupmember Smile (or something like that)

did you work the internal mapper out?

(yes, I know its a thread from 2012.)

Van NYYRIKKI

Enlighted (5918)

afbeelding van NYYRIKKI

26-05-2016, 22:05

mtn wrote:

did you work the internal mapper out?

I have my doubts as it is not quite as easy as mohai makes it sound like...

Van mtn

Champion (265)

afbeelding van mtn

27-05-2016, 01:35

NYYRIKKI wrote:
mtn wrote:

did you work the internal mapper out?

I have my doubts as it is not quite as easy as mohai makes it sound like...

Somewhere, sometime maybe someone equipped with a HG-modded 738 reading this can shed some light upon this Smile
I cant find anything about it in any MSX Brugerklubben discmag or SYNTAX either..

Van Wild_Penguin

Hero (644)

afbeelding van Wild_Penguin

27-05-2016, 09:52

Having done something similar recently with my NMS8255, I know it can be a bit (or a lot) daunting if you have not worked with mappers before. However, I do know where I'd start looking for the information needed, if I was doing something similar.

First, I'd get the SVI738 service manual, which I can not find - the closest I can find is link.

Then I'd compare it to something that has already been done, like the NMS series memory mappers, this project, and other DIY memory mappers. Also, see my experiences in NMS8255 mapper with 4464 DRAM chips.

The main difference with the NMS82XX upgrades is that those upgrades uses 4464 (64x4bit instead of 64x1bit) DRAM chips ... but the most easiest way (if you can source the chips!) would be to use 41256 chips as mohai said, since that is pin compatible. I believe the key is in page 16 of the PDF I linked above. Note that you are missing the whole mapper page selection circuit, which will eb somewhat different to the NMS mappers, since you have 1-bit memory...

Van Xiny6581

Rookie (29)

afbeelding van Xiny6581

27-05-2016, 13:13

Hey MTN Wink
Wow, revoking an old post but that's excellent.
Thing is I haven't really got the time to dive into this since last time. I did some internet searching but yeah made me more confused than convinced Wink So it left me here again.

Van mtn

Champion (265)

afbeelding van mtn

27-05-2016, 14:03

Maybe we should go about to approach this as a coop? Two heads and etc. I guess you have about as little free time as I do though, but that shouldnt be a showstopper only a reason for (atleast me) better planning of time

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