CPU refers to IDT in the real mode. Experiment on a real FM TOWNS 2MX…

… confirmed that 80486 looks at IDT even in the real mode. Return I/O 208H bit 1 FREADY=0 if motor is off to align with the observation from a real FM TOWNS 2MX.

src/cpu/i486templatefunctions.h

@@ -25,7 +25,7 @@ inline void i486DXFidelityLayer <FIDELITY>::Interrupt(unsigned int INTNum,Memory
 		// Push(mem,16,state.EIP+numInstBytesForReturn);
 
 		auto intVecAddr=(INTNum&0xFF)*4;
-		uint32_t CSIP=mem.FetchDword(intVecAddr);
+		uint32_t CSIP=mem.FetchDword(state.IDTR.linearBaseAddr+intVecAddr); // Experiment on real FM TOWNS 2MX confirmed that IDTR is valid even in the real mode.
 		auto destIP=cpputil::LowWord(CSIP);
 		auto destCS=cpputil::HighWord(CSIP);
 		if(true==enableCallStack)

src/towns/fdc/fdc.cpp

@@ -664,7 +664,14 @@ void TownsFDC::MakeReady(void)
 		// 0421:00000BE6 C3                        RET
 		// Therefore, the timing to clear DSKCHG flag is not status-read.
 		// Maybe when a command is written?
-		data|=(DriveReady(townsPtr->state.townsTime) ? 2 : 0);
+
+		// Looks like FREADY flag should be zero when the motor is off.
+		// Based on the observation of real FM TOWNS 2MX.
+		if(true==state.drive[DriveSelect()].motor &&
+		   true==DriveReady(townsPtr->state.townsTime))
+		{
+			data|=2;
+		}
 		data|=0b01100; // 3-mode drive.      [2] pp.809
 		data|=0x80;    // 2 internal drives. [2] pp.773
 		break;