Slot and Memory mapper on SVI 738 DIY to MSX2/MSX2+

Page 2/3
1 | | 3

By gdx

Enlighted (4802)

gdx's picture

09-04-2019, 11:18

I am not talking about an hybride solution (external+internal). If you reverse the signal /SLTSL of internal RAM with that of the cartridge slot. The MSX remains 100% functional without external addition even with an internal MSX2 upgrade. Then you can use a slot expander with a RAM expansion or a MFR+SD or any all-in-one cartridge, the Memory Mapper will be taken as main memory at startup. So it will be more compatible with software that needs a lot of RAM. This is not the case if you do not reverse these signals.

If you upgrade this SVI-738 to MSX2+ you will need to add the mapper for the RAM and the F4 port.

By lkpalwa

Expert (105)

lkpalwa's picture

09-04-2019, 13:44

Its already upgrade to MSX2+ (working, thx @NYYRIKKI for the help) with working RTC and MSX logo boot up Smile
But why should a mapper on SLT3-3 should not be a good option, plus moving the cartidge slot from SLT2 to SLT1
If I look around almost all internal real msx2/msx2+ have slot3 for memory mapper ?
AND of course the F4 will be added, I works just now with patched BIOS without F4 support

I now waiting for images Smile - so please help (some one have to have a GILVAD modify version
Crazy Crazy Crazy Crazy

By gdx

Enlighted (4802)

gdx's picture

09-04-2019, 14:19

What is important is that the internal RAM is placed in an upper slot than the slots of cartridge ports.

By lkpalwa

Expert (105)

lkpalwa's picture

09-04-2019, 20:03

then slot 3-3 should work perfect - see IC63 Smile
[img][/img]

By lkpalwa

Expert (105)

lkpalwa's picture

09-04-2019, 20:05

I will test this out have got some images from Bjørn Boye Skjoldhammer (thx)
Have seen that in the 1MB mapper he use this signal also Smile

By NYYRIKKI

Enlighted (5889)

NYYRIKKI's picture

09-04-2019, 23:48

lkpalwa wrote:

But why should a mapper on SLT3-3 should not be a good option, plus moving the cartidge slot from SLT2 to SLT1

In theory it is a good idea and worth working for...

I think the major problem is the signal coming to pin 5 of IC42... If you trace that you'll see that is comes from this mystic IC52... and if you take a bit closer look you will see that only address lines coming in to this chip are A0,A1,A6,A14 and A15... From that you should be able to do the math... Everything is not quite complete.

By lkpalwa

Expert (105)

lkpalwa's picture

10-04-2019, 12:25

okej I may have a solution looking at expert3 schematics for slot handling and compare to SVI tech note Smile
Question is we could skip some logic and just use the D0-D7 lines with some of the logic there
will attach images as soon a get spare time at lunch/afternoon - thx for the direction NYRIKKI Smile

By lkpalwa

Expert (105)

lkpalwa's picture

10-04-2019, 16:47

so here is the expert3 schematics, plan is to just add a extra LS153 + LS139 in schematics U57 and U58B and use D0-D7 and A14-A15 direct instead of going through LS273 (that logic is not needed here I think oO )

the reuse linjen (signal from SVI see schematic below in expert3 its IC U42B and U45C vs SVI IC 42 )

and finally on IC35 switch SLT2 with SLT1 (to cartidge on SLT1) and instead on RAMSEL use the SLT3-3 signal above

will test this and come back with results later this week - any suggestion appreciated

By lkpalwa

Expert (105)

lkpalwa's picture

10-04-2019, 16:52

NYYRIKKI any ideas or problems as you see on this, when my function works PCB will be orders, if you want I will try to order for you to Smile or any one interested on the MOD Tongue , and next implementation is DOS2.x and FMPAC on board also Smile
Glue logic is traditonal LS chips, final version will be CPLD to keep it clean and small Smile

By alexito

Paladin (746)

alexito's picture

10-04-2019, 17:04

I'm interested in any kind of mod for my lovely SVI738 with just 128KB VRAM upgrade done.

Crying

I'm IN my money is yours.

Page 2/3
1 | | 3