HB-F1XD Japanese MSX2 - Replace V9938 with V9958?

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By Colemu

Hero (535)

Colemu's picture

09-09-2012, 22:33

In other words the exact same complete rom as the F1XDJ placed in the F1XD? Question I wonder where I could obtain this complete rom image, and what Eprom I would need to flash it to??

What about this one:
http://www.ebay.co.uk/itm/27C512-BRAND-NEW-BLANK-EPROM-M27C5...

27C512 (64k x 8). The roms I have are:
f1xjbios.rom (32k)
f1xjdisk.rom (16k)
f1xjext.rom (16k)
Total (64k)

No idea how to put these images together in the right order as one complete rom however!!

By RetroTechie

Paragon (1563)

RetroTechie's picture

09-09-2012, 22:36

I think most logical sequence would be:

  1. Replace videochip with V9958 (there's some how-to documents floating around, also see V9958 databook for changed pins versus V9938). Fairly simple apart from the (de)soldering job. Some software uses the 2+ videochip without 2+ ROMs present, and this upgrade doesn't get in the way of later upgrades.
  2. Add circuit for the 1-bit I/O port (F4h) that's used for MSX2+ soft/hard reset, if you want. You can test function without affecting behavior of the machine, since MSX2 ROMs don't use this.
  3. Use emulator to test the 2+ ROMs that you plan to use (and correct behavior versus that 1-bit I/O port missing or added).
  4. Put those ROMs in the machine.
  5. Add a 512K * 8 bit SRAM.

If any of the above seems too difficult, skip that part (but still follow above sequence).

Colemu wrote:

Just checked the Basic chip is LH531067

That's a 1 Mbit (128 KB) ROM like Jipe said. Exactly what contents & how the blocks are arranged in the chip... dunno. Perhaps the easiest way to find out would be to put it into a megaROM game cartridge & read contents.

I have a 1 Mbit ROM for Japanese 2+ machine (Sanyo Wavy PHC-70FD2) on file. It wouldn't surprise me if block ordering is the same in these ROMs used for MSX2 machines, but I'm not sure about that. Maybe someone else knows or already has the exact contents of this ROM on file? That is: as 1 piece, with blocks ordered like in original chip.

Quote:

the 27c400 are a different size, however my 27c256 eproms are an exact fit (28 pin). Is this eprom a feasable replacement?

Nope. For an MSX2+ (with FDD), contents adds up as follows:

32K BIOS/BASIC
16K MSX2 subROM
32K extra ROMs for 2+ (boot logo, BASIC extensions etc)
16K diskROM
16K FM-BASIC
16K KUN BASIC compiler
-----
128K = exactly 1 Mbit, how convenient...

So for an MSX2 it fits in 64K but they still used a bigger ROM. Maybe different versions in the same ROM chip (mass volume!), maybe some optional parts, who knows.

For replacement you could use a combination of EPROMs (for example 27C512 + 27C256). Or a 1 Mbit EPROM (27C010, 27C1001, or a 1 Mbit Flash ROM), possibly with some additional logic to select the correct blocks. 128K * 8 bit EPROMs are all 32 pins, am I correct there's room for that on the board? (holes to place a 32-pin IC, that is)

Quote:

Another one in the FDC section is TMS2793NL, MAS 74503 (20PIN, same size as my 27c400 eprom), is this the disk ROM?

??? Doesn't ring a bell, and Google has nothing either. Next to that MAS 74503, what IC# is printed on the board? (to find in schematic) And how do you mean "20 pin, same size as 27C400" ? 2 rows of 20 pins on each side? Rows the same distance apart? Is that IC on the floppy drive or on main board?

By Colemu

Hero (535)

Colemu's picture

09-09-2012, 22:58

Thanks a lot mate.

A lot to think about here, not such a small project after all LOL!

I forgot about Jipe's info, apologies Jipe. Seems logical to have all models having the same size rom for mass production etc.

You have all provided me with lots of info to get me started, it's much appreciated! Smile2

By NYYRIKKI

Enlighted (5900)

NYYRIKKI's picture

09-09-2012, 23:39

I would say: Forget Kanji ROM, forget boot logo (requires patch to EXT-ROM... Untested, but try to put #C9 to offset #2C76), forget F4-port, forget FM-BASIC and forget KUN BASIC compiler (Ok, I like KUN BASIC, but you can load it from disk when you need it)

The correct ROM order is most probably "bios, ext, disk" or "ext, disk, bios"
To find correct order for sure you have to dismount the original ROM and read the content on EPROM writer or try to find schematics.

Make sure you can make the modified HB-F1XD configuration to boot in OpenMSX emulator before you try to burn the ROMs. Trying in emulator is much more easy...

By msxholder

Champion (394)

msxholder's picture

09-09-2012, 23:47

Never seen schematics or service manuals outside europa. is there nobody in the land of the rising sun with service manuals ????!!!

By Colemu

Hero (535)

Colemu's picture

09-09-2012, 23:51

Thats what I was hoping for, these would fit on 27C512 eproms. I have a programmer to work with these too.
I will try open MSX, I use blueMSX at the mo, but it's no good for this purpose.

Only thing I need to know is how to combine these roms into one image for flashing to the eprom?

Anyone Question

Or someone could offer to do it for me.... (fingers and toes crossed!)

By NYYRIKKI

Enlighted (5900)

NYYRIKKI's picture

09-09-2012, 23:54

Colemu wrote:

Only thing I need to know is how to combine these roms into one image for flashing to the eprom?

In Windows command shell:
COPY /B 1.ROM+2.ROM+3.ROM ALL.ROM

In MSX you need to use external program from DOS-disk called CONCAT... parameters are same.

By Colemu

Hero (535)

Colemu's picture

09-09-2012, 23:59

Great! How do I patch the ext rom? so that I don't need the logo?
Software to edit rom etc... Question

By NYYRIKKI

Enlighted (5900)

NYYRIKKI's picture

10-09-2012, 00:09

Colemu wrote:

Great! How do I patch the ext rom? so that I don't need the logo?
Software to edit rom etc... Question

I use this program:
http://www.chmaas.handshake.de/delphi/freeware/xvi32/xvi32.htm

... but if you want to use Windows / DOS default tools then you can write:
DEBUG EXT.ROM
E 2D76 C9
W
Q

(Ps. Note the #100 offset caused by DEBUG-command)

By Colemu

Hero (535)

Colemu's picture

10-09-2012, 00:32

Opened the rom with the program you suggested, however, I haven't got a clue what I'm doing! oO

Burned plenty of roms etc, but never edited one. HEX means nothing to me...

Can you talk me through it, or could you patch it for me?

Once I have the working rom, burning and installing should be no problem Smile

These are the images I'm using:
http://www.msxarchive.nl/pub/msx/games/roms/system/openMSX/S...

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