If I recall properly, the hassle is in missing RTC.
Anyone knows why problem happens, and what to modify in ROM to make it running without RP5C01. Thanks.
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If I recall properly, the hassle is in missing RTC.
Anyone knows why problem happens, and what to modify in ROM to make it running without RP5C01. Thanks.
i know a set of roms without RP5C01 exist for CX5MII
http://msxinfo.msxblue.com/msxsvi738.html
see : another msx2 conversions -> ROMS
Well, I have removed some code in the ext rom which checks for RTC, and in bluemsx combination works (Enable CMOS and Use charged battery are both unchecked). However the same ROM combination, installed into the real MSX does not work - no picture at all. Are there any other MSX2 ports missing where it can hang?
msx2 without memory mapper? hmmmmmm
to be msx2 IIRC must be a memory mapper, don't matter if you just use 4 pages (64KB DRAM).
another register, the F4, but I don't remember if that will lockup the booting.
so, the memory mapper if your target.
Memory mapper isn't required for MSX2 (only for MSX2+), and there exist several MSX2 models that have 64K main RAM but not as memory mapper.
F4h I/O port (1 bit) serves for soft/hard reset detection on MSX2+/Turbo-R machines.
So no problem there. Oh, and IIRC the MSX-DOS ROM also accesses RTC I/O ports, and asks user when not there (for timestamping files).
Are there any other MSX2 ports missing where it can hang?
V9938?
V9938 = yes, it is by default in this MSX1.
Machine does not get to VRAM initialization - its R/W line is always high. It does not get to VDP at all - /CSW (30) and /CSR (31) are always high. (and of course CAPS led does not work...)
Solved. There was resistor R315 missing (4.7K, pull-up for EXT ROM's PGM pin 27), which is not documented in any version of the family of these machines.
That was not the last problem. System did not work properly and I found ou that Guillermo was right - some chips related to memory mapper were missing on the board. 
Now my problem looks like:
In screen 2 and 3 everything is fine.
In higher screen modes sprites (only sprites!) are corrupt and flashing. I tried with King's Valley 2 and Usas. Why could it be? Important to mention that I replaced DRAMs with 2 SRAMs of 64K each (with some addon logic to keep proper signalling of SRAMs according to /RAS and /CAS signals).
you modify which model of MSX ?
if CX5MII the original have 16k Vram it's easy upgrade to 64k or 128k
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