Putting MSX2 ROMs into MSX1

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By Eugeny_Brychkov

Paragon (1232)

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09-10-2010, 13:33

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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By Jipe

Paragon (1594)

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09-10-2010, 14:06

i know a set of roms without RP5C01 exist for CX5MII

By Jipe

Paragon (1594)

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09-10-2010, 15:23

http://msxinfo.msxblue.com/msxsvi738.html

see : another msx2 conversions -> ROMS

By Eugeny_Brychkov

Paragon (1232)

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10-10-2010, 01:05

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?

By flyguille

Prophet (3031)

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10-10-2010, 04:19

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.

By RetroTechie

Paragon (1563)

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10-10-2010, 07:21

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?

By Eugeny_Brychkov

Paragon (1232)

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10-10-2010, 08:22

V9938 = yes, it is by default in this MSX1.

By Eugeny_Brychkov

Paragon (1232)

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10-10-2010, 10:26

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...)

By Eugeny_Brychkov

Paragon (1232)

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10-10-2010, 10:58

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.

By Eugeny_Brychkov

Paragon (1232)

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10-10-2010, 17:22

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. Crying

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).

By Jipe

Paragon (1594)

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10-10-2010, 18:18

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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