Hello, i´m just planning to build a new internal Cartidge Slot into Msx2 HB-F9s, to use it in near future for Sound Card LPE-SANS V2 or MC-SD Sinfox V2.2.
About the Sound Card LPE-SANS V2 i read in the manual that for Record games this cart will be in Slot 1 Not Expanded , i think that will be great if i could install this cart into the MSX, the cart is a little big and did not have a palstic case housing, the best point will be to install the cart stereo output in the MSX2 HB-F9s case, the problem is that, for record operations the cart will be inserted in Slot 1 (not expanded) i hope this will not a problem to allocate in the new internal slot.
About the MC-SD Sinfox V2.2 the manual says that any primary or extended Slot can be used.
I think the best way to install the internal Cart will be use a female Msx Cartidge conector, wire all its pins and try to allocate in any free place in mainboard MSX component side. Then i will need to wire all cart signals to the female conector, this way in future i´ll change the internal cart inserted more easy.
So I think I should install the internal cartridge slot using it as primary slot and not expanded slot, i wonder if this will be possible using the Slot engine Signals like SLOT33 or SLOT0/00 to install internal cart like primary, or i will need to use a programed CPLD with all slot expander functions. Will be great have the greatest possible compatibility in the internal slot.
Ok, for now i´ll check in the Hb-F9s which pins are the same between cartridge slots 1 & 2, almost of them (you´ll see in red in the image below), there are several pins that do not match between the Slots and are connected to different components. This signals that i found are:
-------------------------SLOT1----------------------------------
Pin 10 <BUSDIR> goes to <R65>
Pin 4 <SLT1> goes to <pin51 (SLT1) in S1985>
-------------------------SLOT2----------------------------------
Pin 10 <BUSDIR> goes to <R144>
Pin 4 <SLT2> goes to <pin52 (SLT2) in S1985>
Also i read some points in the S1985 datasheet about slot expansion, then i did the diagram more below but i dont sure if this will be correct and if works like a primary or expanded slot.
Possible Diagram install (i dont sure if this is correct):

I didn´t find the MSX2 Technical Databook, i cant find this nowhere and will be interesting know more about the Slots.
Regards.

do you really need to insert more than 2 cartridges at the same time, in a machine that has a turbo upgrade, no bus buffers, and internal RAM expansion (so you don't ever need external mapper inserted) ?