Dumping/reverse engineering MSX models thread

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Par mars2000you

Enlighted (5818)

Portrait de mars2000you

14-02-2021, 16:28

There is a chip on the underside of the PCB, a VLC9007, no idea what it is exactly.


More pictures here: https://www.retropix.com.br/olhando-dentro/msx-sanyo-mcp-3-w...

Par DamnedAngel

Master (213)

Portrait de DamnedAngel

14-02-2021, 19:24

Oh, I forgot about that one. My bad.

I have no idea on how to test it, though. If someone has any idea let me know

Par sdsnatcher73

Paragon (1646)

Portrait de sdsnatcher73

27-02-2021, 13:22

I just discovered something odd regarding Kanji ROMs on my PHC-77 (and possibly also on HB-T600 that I reported earlier having issues with the Kanji ROM). It seems flash cartridges are interfering with the on board Kanji ROM. At least Carnivore2, GR8NET and Flashjacks are causing this issue on the PHC-77. See photos of the onboard MSX-Write with the flash carts inserted and 1 with RDNX (which is simpler and this does not interfere).

Par Manuel

Ascended (17681)

Portrait de Manuel

06-03-2021, 13:15

We noticed that in the Sanyo PHC-77, MSXMEM reports a 0kB memory mapper.

Theory is that this is caused by having no memory mapper, but still an S1985 in the system, which implements part of the memory mapper registers anyway.
I know of the following machines that have S1985 but no memory mapper:
National FS-4500
National FS-4700
National FS-5500F1
National FS-5500F2
Panasonic FS-A1
Sanyo PHC-23JB
Sanyo PHC-77

It would be useful to find out how this works exactly. As Wouter put it:


If it is indeed because of the 0xfc-0xff IO ports, and if so, how exactly do those port behave?
My best guess: the lowest n bits of those ports reflect the last written value to those ports and upper bits always read as '1'.
To test in BASIC: OUT &hfc,0 : print inp(&hfc)
or try with some other values than '0' and maybe confirm with another port in the range 0xfc-0xff

Can someone who has any of these machines help with this?

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