Yamaha CX-11 upgrade to MSX2

Página 2/4
1 | | 3 | 4

Por NYYRIKKI

Enlighted (5382)

Imagen del NYYRIKKI

22-07-2018, 00:29

Alexey wrote:

The MSX2 must have 128kb or RAM. Your computer has 32kb only. And you can't easily change that because you only have four x416 RAM chips on board. To install 128kb you will need four x464 chips and a mapper circuit.

You can run most Japanese MSX2 games without memory mapper. This 128KB RAM was actually very European thing.

This 32K RAM problem is anyway something you have to fix sooner or later in order to full fill MSX2 minimum specs... (but try to make the computer boot up first... 32K is more than enough for that. MSX2 can actually boot even with just 8K RAM)

Quickly about the RAM in order to get the idea... You can replace pair of the x416 chips with two x464 chips, but you also need to reconfigure the slot layout so that the RAM will be moved to slot 3-2. Worst part of the story is that you need to jump wire a NAND chip to 7 address lines in order to provide subslot information back to the MSX-engine /RSEL terminal. In order to refresh 64K you need to replace those RAM chips that currently use CAS2E signal. This action will also move your SFG-01 module from slot 3 to slot 3-0.

When you get this to work I suggest that you put the SUBROM on top of main ROM and wire the signal that you have now in /SLTSEL in to the MSX-engine /SLT01/31 pin... Anyway... move just one step at a time in order to avoid problems.

Por Alexandre_Taito

Champion (325)

Imagen del Alexandre_Taito

22-07-2018, 00:30

Wow, lots of people helping! But unfortunately, it isn't that simple

Firstly, the CX11 is a WHOLE different beast than YIS503/II or CX5M/128.
Motherboard: https://www.flickr.com/photos/140652193@N07/26554818890/in/d...
Album: https://www.flickr.com/photos/140652193@N07/sets/72157667354...
(photos aren't mine, but Max Vaslov's).

So, I did already:
- Upgraded VRAM to 128K. Since it is a MSX1, I can't test if it is OK with testmem. Anyways, I tested the 4 4416 chips on SimCheck before installing.
- Created a two-stories MSX2 rom with no-RTC and no-F4 register code. I cannot guarantee if these roms are correct beyond testing on BlueMSX. If you have a MSX2 set which is **guaranteed** no-rtc and no-F4 modded, please drop me a mail. Thanks in advance!
- X3527 DOES NOT HAVE THE SLOT EXPANDER ENABLED. It needs (By the S3527 manual) some address NANDed and input to a pin (/Rsomething I dont remember now, but it is in the S3527 manual). So I'm using CE and OE together connected to slot1 (or slot 2) /SLTSEL
- I used a SD/Mapper to have more than 32K of RAM

And until now, nothing works. Of course, I can put the MSX1 ROM back and it works with no problems, run SD/Mapper, play games, etc.

So, I'm a bit lost. I could use some help here :) I'm not the brightest apple in the pack, but I've done lots of 2.0 and 2+ transformations before. Any tips?
Thanks!

Por NYYRIKKI

Enlighted (5382)

Imagen del NYYRIKKI

22-07-2018, 00:49

Alexandre_Taito wrote:

- Created a two-stories MSX2 rom with no-RTC and no-F4 register code. I cannot guarantee if these roms are correct beyond testing on BlueMSX. If you have a MSX2 set which is **guaranteed** no-rtc and no-F4 modded, please drop me a mail. Thanks in advance!

Actually F4-port is not required by MSX2. This is MSX2+ stuff... The RTC is the thing that I think is now most likely to kill your setup... In BlueMSX this stuff is in a bit weird place. Please go to the "Machine Configuration editor", go to the last "Extras"-tab and uncheck the "Enable CMOS". This should tell if your ROMs actually boot fine without RTC or not. Please note that you have to modify something else as well back/forth in order to activate "Save"-button.

Por NYYRIKKI

Enlighted (5382)

Imagen del NYYRIKKI

22-07-2018, 01:33

... and if you have more MSX-computers, try to attach your cartridge to some other MSX and see if you can actually verify it is displaying correctly in the address space. (ie. use ROM dump tool to read it from MSX perspective) Unfortunately there is no more in this story... The full checklist is:

- Verify VRAM working (done)
- Verify MAIN BIOS is ok and correct version. (Unlikely source of problem)
- Verify SUB-ROM is correct version, visible and displaying correctly in memory space (the RTC code is originally here)
- Verify all the physical connections (ie. bend / not well connected pin may also be a cause)

There really should not be anything else to be done. If you are still out of luck you may also try to explain here in more detail what "it does not work" means to you, what ROMs you have used etc.

Por Alexandre_Taito

Champion (325)

Imagen del Alexandre_Taito

22-07-2018, 03:19

NYYRIKKI, thanks for help, but all of this has been tested. MAYBE and I say MAYBE there is a problem with the ROMs I used. But I used the same ROMs in BlueMSX and they boot OK. I got a MSX1 computer (CX5M), put 32K of ram in the same slot of main rom, nothing else, no CMOS (thanks for telling me where the RTC thing is), as plain as possible. And the subrom I put into cartridge, using "insert cartridge". Bang, MSX2 booted imediately.

I'm really confused about what is wrong in my setup. But I'm going down to lab right now and i'll try to make it work again
I never had so much trouble to convert a computer to MSX2 :\

Por Alexandre_Taito

Champion (325)

Imagen del Alexandre_Taito

22-07-2018, 03:40

Update: It worked. I'll try to understand what happened and I'll come back here :\

Por Alexandre_Taito

Champion (325)

Imagen del Alexandre_Taito

22-07-2018, 04:10

Ok, working, validated. But there is something that is intriguing me.

I have two eproms. Lets call it M (from Main) and S (from sub).

Put M on place of MSX1 original rom. Put S into a cartridge board, CE/OE together connected to /sltsel. Boots OK, testmem reports everything is working, it works.

Put M on place of MSX1 original rom, with a 28 pin socket piggybacked on it (so I can test subrom). Pins 1 and 27 are pulled and connected to VCC. CE/OE of the S rom on socket are also pulled and connected to /SLTSEL. Computer does not boot.

There are no bad contacts, interrupted wires, nothing. I cannot understand what is going on. Will beep the board to see if there is something which is connected thru another IC. But it shouldn't happen.

Por Alexandre_Taito

Champion (325)

Imagen del Alexandre_Taito

22-07-2018, 06:08

More tests:
- Connected the sub rom to /CS1 and /SLTSEL as it is on the CX5M/II service manual. Nop.
- Expanded the 0 and 3 slot adding the 74LS30 to create the /REXP signal. No cigar.
- Verified the expanded slot is working because I can boot MSX BASIC with the sub rom on a cartridge, so I can run TESTMEM. It says correctly the memory is in slot 0.x or 3.x, so slot expander seems to be working

Any tips?

Por Alexandre_Taito

Champion (325)

Imagen del Alexandre_Taito

22-07-2018, 06:24

Ok, found the problem.
The problem seems to lie in the buffering of the databus. If I use an "external" (i.e.: Pos-data bus buffer) slot, it only works with the eprom on the external slot.

- Expanded the slot 3 cutting the flying diode and adding the missing 74LS30 to drive /RSET
- Connected CE/OE of the sub rom to slot 3.3
- Works flawlessly.

Complete tutorial, expansion boards gerbers and all the info soon in https://tabajara-labs.blogspot.com
Thanks you all for your effort to help!

Por NYYRIKKI

Enlighted (5382)

Imagen del NYYRIKKI

22-07-2018, 11:03

Ah, yes... In external slots there are usually buffers to prevent databus contamination. It was the "MSX 2.0 SUB-ROM in slot, CE/OE connected to /SLTSEL" that made me think that you are actually using physical external cartridge to mount the chip.

Anyway... Congratulations! Very good to hear it is working!

I also think adding the 74LS30 was not done in vain. Applications usually hate when the RAM is in slot 0. (Ok, you said you have also external mapper, but some program may still find it, if it just seeks for the first RAM it can find.) Generally the problem is not that bad when you don't have slot 0 expanded, but having RAM in expanded slot 0 is the worst configuration you can make. Many MSX1 cassette games don't work at all if you have slot 0 expanded and placing RAM in there is even worse.

I believe that your unfortunate RAM situation is now that you have 16KB in slot 0 bank 3 and another 16KB mirrored to all banks of slot 3-2(?)

I still suggest that you change 64K RAM chips to those /CAS2E locations and disable the other two 16KB chips that are using /CAS3. This will make it 100% valid MSX2 configuration that can be expected to work nicely even when there is no SD+RAM-interface connected.

If you are not planning to use it at all without external RAM, I think you can just disable all internal RAM to prevent it from causing headache to applications that try to figure out what is going on.

Página 2/4
1 | | 3 | 4