F4 port board for MSX2+

Guardian (3571)

28-05-2015, 22:28

The F4 port is not required, but very much desired on MSX2+. Usually making this port when converting MSX2 computers to MSX2+ requires heavy rewiring of system's logic and adding new components on top of existing ones. It appears that Kamil Karimov (a.k.a Caro) has designed a simple board that could add F4 register to MSX2+ without major hassle. All you need is to solder 4 microchips in SOP form factor and a few SMD components on a small board and then connect this board to Z80's outputs. Below is the schematics and the board's picture.

As you might see, the board has the same size and form factor as Z80 chip, so technically it can be soldered on top of the processor. Not very complicated for a skilled person who decided to upgrade his MSX2 to MSX2+.

Please note that I have not tested this board myself yet, but so far everything that Kamil has been creating worked for me. The guy is a genius! So if someone wants to purchase this board for a very small fee, please send me an e-mail. Only 8 boards are available. I may be able to assemble a couple of boards from the components I have, but the price will be, of course, different.

Alexey

By MicroTech

Champion (388)

29-05-2015, 09:59

What a cool idea! First time I see this kind of "extreme hacking"

By Wierzbowsky

Guardian (3571)

29-05-2015, 20:19

Ok, I have components for 4 boards. One board with all components (do it yourself kit) - 10 euro. Shipment within EU is 2 euros. I will also assemble 2 boards myself, so if someone needs them, please send me an e-mail. A fully assembled board is 15 euros.

As said before, I give no guarantee that this will work as I haven't tested the boards myself yet. So you are using the board on your own risk.

Alexey

By Wierzbowsky

Guardian (3571)

29-05-2015, 22:35

And here's the pic of assembled boards.

Alexey

By ARTRAG

Enlighted (6933)

30-05-2015, 09:59

What is thus port for on msx2+?

By Grauw

Ascended (10711)

30-05-2015, 10:59

It’s the system flags port, the MSX2+ BIOS requires it. So this board is very useful for people who want to upgrade their MSX2 to MSX2+.

By l_oliveira

Hero (534)

02-06-2015, 18:06

Just mount a socket on top of the board plug the Z80 there. At the bottom plug a pin header and then it sits on the middle of the way between the system and the Z80 chip.

A lot of Amiga expansion devices would connect to the computer that way.

By Wierzbowsky

Guardian (3571)

02-06-2015, 18:33

Nice idea, but unfortunately in all MSX machines I've seen the Z80 processor was soldered to the board. So mounting a socket on top of Z80 and then plugging the F4 board with soldered jumper pins into that socket could be possible. However this may cause some problems if Z80 gets too hot under the socket.

By l_oliveira

Hero (534)

02-06-2015, 18:37

Most Z80 chips don't even get warm. A few do (old Sharp ones for example). But that's not so common.

By Wierzbowsky

Guardian (3571)

28-02-2016, 19:10

Guys, has anyone who has got this board from me actually tested it in MSX computer? I assembled the F4 circuit on the FMPAC/F4 combo board, but I am still getting 255 (inverted 0) from the F4 port of MSX. So the circuit does not seem to work...

By Wierzbowsky

Guardian (3571)

28-02-2016, 23:30

I verified the small F4 register board with my Yamaha MSX2+ by putting it under our FMPAC combo board:

Seems to work properly even in this "sandwich" mode. Looks like the F4 curcuit on the FMPAC combo board may have some problem and needs to be diagnosed. But the good thing is that the small F4 board can be put under the FMPAC board without any sweat, it sits very tightly and doesn't even need to be soldered.