MSX2(+) upgrades

MSX 2(+) conversion

Convert to MSX2+ by replacing the V9938 with a V9958 and add the F4 register required by Basic 3.0

pdfBuild a v9958 into a NMS8250/55
pdfBuild a v9958 into a NMS8280
pdfBuild a v9958 into a HB-700
pdfAdd the F4 register

Notes by JP Grobler on converting his NMS8250 to a MSX 2+:(with lots of help by Hans Oranje)

I got the v9958 vdp and had the v9938 removed & replaced with a shrinked dip socket at a TV repair shop (2Euro)

On the v9958 (connections were done on the chip itself!):

Pins 1, 4, 27 GND
Pins 21, 58 +5V Capacitor 100nF between pin 21 and pin 20 (Analog GND).
I only had 27512 eproms and burned Basic 3 + Bios Sub roms into it.
On the 8250:
IC 119 = Main rom
IC 118 = Subrom
IC 117 = Diskrom
I only replaced IC 119 & IC 118
IC 118 socket:
Pin 1 (A15) is connected to +5V
Pin 27 (A14) is connected to +5V
Do not connect these pins of the eprom to the socket!
Add wire between Pin 1 (A15) and the unused
slot connector (MY) Pin 42 (5th from right)
Add wire between Pin 27 (A14) and the unused
slot connector (MY) Pin 41 (5th from right)
IC 119 socket:
Pin 1 (A15) is connected to +5V
Do not connect these pins of the eprom to the socket!
Add wire between Pin 1 (A15) and Pin 16 (GND)
Add the F4 latch: see Hans Oranje instructions

The source of these instructions is Hans Oranje!

Note by Erik Luppes:
In the instructions MY connector pin 41 and 42 is mentioned the MY connector only has 40 pin
– pin 41 must be 32 = A14
– pin 42 must be 31 = A15

These ROMS are published here with permission from Hans Oranje.
pdfROMS used by JP Grobler for MSX 2+ Basic 3.0

Hans Oranje not only adapted the MSX2+ ROMS to the international standard as used in dutch MSX machines, he also adapted for german MSX machines (for example keyboard mapping).
pdfGerman MSX BASIC V 3.0 ROMS made for Franz Schiefer Austria and used in the NMS8280
Complete according to the SONY Technical Databoek

Thanks to Jipe, ROMs for VG8235 MSX2+ + No F4 port (triggered by Giorgio Sagias):
pdfVG8235-19 MSX2+ ROMS (Jipe, AZERTY keyboard layout)

pdfVG8235 MSX2+ ROMS  (Jipe, QWERTY keyboard layout)

Dutch article how to perform the MSX2+ conversion
pdfMSX2+ conversion

The instructions to convert the SVI 738 to MSX-2 also in english, combined the CUC dutch (translated) info and the danish/finnish info
pdfConvert the SVI 738 to MSX-2

pdf A patched extended ROM for the SVI 738 or MSX1 without clock chip and with “memory counter” instead of the original 64k also for CX5M by Uwe Neisius

Convert Yamaha CX5M to MSX-2
pdfConvert Yamaha CX5M to MSX-2

pdfA complete BlueMSX profile of the Yamaha CX5MII by Uwe Neisius

Dutch article: MSX 2+ ombouw: de hardware
pdfMSX 2+ ombouw: de hardware

Patch by NYYRIKKI on 50/60 HZ selection on boot on a 825x/8280

Needed modifications to NMS8250 SUB-ROM:

#0422: 8C,3E
#3E8C: CD, 3C, 06, DB, AA, E6, F0, F6, 03, D3, AA, DB, A9, E6, 20, C8, AF, 32, E8, FF, C9

While boot logo is displayed, push “H”-key down untill beep to start in 50Hz mode, otherways 60Hz mode will be selected.

If you want to change also boot logo to 60Hz, put 0 to #2B56

MSX-2+ ombouw (dutch detailed articles)

MSX-2+ voor de Philips NMS 8250/55
MSX-2+ voor de Sony HB-F700P/D
V9958 MSX-2+ videochip in Philips NMS 8250/55
V9958 MSX-2+ videochip in Sony HB-F700P/D

Notes by Philip on converting the NMS8245 to MSX2+

Installing the v9958

Cut out the v9938, remove the remaining pins and solder.
Solder a socket in place of the v9938

On the v9958 these pins have to be bend so they are not inserted into the socket:
4 (vreset) (Should not be needed as it does not seems to be connected in nms8245…)
26 (wait)
27 (hreset)
21 (vdd)

Then connect these pins together on the v9958:
1, 4 and 27
21 and 58

Installing the ROM

Since there is no F4 port, make sure the F4 port stuff is disabled in the BIOS.
Create a 27c512 or similar system rom with this layout:
0000-7fff basic-bios
8000-bfff subrom
c000-ffff diskrom

For the kanji rom I’ve used a 27c512 but a 27c256 should also work.
It should have this layout (for a 27c256 just skip the 2nd half):
0000-3fff kanji rom 2nd 16k block
4000-7fff kanji rom 1st 16k block
8000-bfff kanji rom 2nd 16k block
c000-ffff kanji rom 1st 16k block

Insert the system rom in the rom socket.
Bend pin 27, 20 and 22 on the kanji rom and install it on top of the system rom.

Connect the bend pins as following:
– pin 27 on A14 i.e. pin 25 cartridge slot
– pin 20 on CS12 i.e. pin 3 cartridge slot
– pin 22 on slt3/30 i.e. pin 48 of the gate array. There is a nice place to solder it right above pin 48.