Yamaha CX5MII/128 Upgrade to MSX2

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Van Manuel

Ascended (18161)

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12-11-2007, 18:44

grit - could you write a new or updated upgrade guide?

Van grit

Resident (53)

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13-11-2007, 08:18

I was planning on that but.... I got a rom which stated 64K main memory so I thought; 'well it works, let's change that too' I put in another rom and now it does NOT work anymore. Problem is I tried various roms to see which one worked and now I don't know which one it was originally . I suspect it were the Lois C Grosso roms from hansotten.com (which had a slightly different keymap by the way) As stated above I also directly 1-1 copied the roms from my 8280 but that was a no go. Maybe because my CX5MII lacks RTC? Checked the address of the extrom when I put in the original MSX1 rom but that all looked fine. When I have a working rom I'll write it up.

Van Manuel

Ascended (18161)

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13-11-2007, 08:57

Thanks in advance! Smile

Van grit

Resident (53)

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13-11-2007, 09:43

Well, I can verify that the Grosso Roms are working but I can't call it 100% yet, the keys are not mapped correctly (-I have a USA version CX5M) and the 64KB main ram is a bit annoying. I think I'll better see where I can adapt the 8280 roms for no-rtc use...

Van Jipe

Paragon (1504)

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13-11-2007, 15:26

search a breaking VG8235 and desold all clock component
resold on a pcb in your CX5MII
is not easy but after you have a real MSX2 with clock and set screen work
see schema of 8235 and copy

Van grit

Resident (53)

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14-11-2007, 21:28

I was just going to ask you where the * you got the Ricoh chip and I was also wondering how you adjusted the trim capacitor on you rpictures but now it all makes sense.

Van dicksch

Supporter (6)

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14-11-2007, 23:56

Has anyone thought about a pic chip emulation for the clock chip, since they are as scarse as hens teeth?

Van grit

Resident (53)

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15-11-2007, 21:13

Well, I don't know what's tougher, getting a PIC to do this or finding an MSX2 or Amiga to butcher....

Van grit

Resident (53)

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16-11-2007, 12:26

Here I've put a little writeup on the conversion:
http://www.cx5m.net/msx2/xc5m_m2.htm

Van Manuel

Ascended (18161)

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16-11-2007, 15:11

Are you saying that the original has 64kB VRAM?? AFAIK all MSX1's with V9938 have 16kB VRAM. There's no reason to add anything bigger anyway...

Great write up though!

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