diff --git a/boot/Makefile b/boot/Makefile
index ef89990..77041f0 100644
--- a/boot/Makefile
+++ b/boot/Makefile
@@ -5,7 +5,7 @@ PROG = boot
 SRCS = srt0.S gdt.S boot.c
 OBJS = srt0.o gdt.o boot.o
 
-ESRCS = console.c print.c a20.c time.c
+ESRCS = pccon.c sricon.c print.c a20.c time.c
 OBJS += $(ESRCS:.c=.o)
 
 include $(SDIR)/Makefile.inc
diff --git a/boot/a20.c b/boot/a20.c
index 3fa537c..72ebb18 100644
--- a/boot/a20.c
+++ b/boot/a20.c
@@ -1,4 +1,5 @@
 #include <u.h>
+#include "dat.h"
 #include "fn.h"
 
 #define I8042_DPORT 0x60
diff --git a/boot/boot.c b/boot/boot.c
index 4a29add..1ea7e52 100644
--- a/boot/boot.c
+++ b/boot/boot.c
@@ -2,8 +2,11 @@
 #include "dat.h"
 #include "fn.h"
 
+static void coninit(void);
+static void machdep(void);
+
 void (*probe1[])(void) = {
-	a20up,
+	a20up, coninit,
 };
 void (*probe2[])(void) = {
 };
@@ -13,13 +16,41 @@ BootProbe probes[] = {
 	{"disk", probe2, elem(probe2) },
 };
 
-ConDev condev = {
-	.getc = pcgetc,
-	.putc = pcputc,
+ConDev contab[CON_END] = {
+	{
+		.probe = pcprobe,
+		.init = pcinit,
+		.getc = pcgetc,
+		.putc = pcputc
+	},
+	{
+		// serial console
+		.probe = comprobe,
+		.getc = comgetc,
+		.putc = computc,
+		.init = cominit,
+	},
 };
+ConDev *con = &contab[0];
+
+static void
+coninit(void)
+{
+	ConDev *p = con;
+
+	for(int i = 0; i < elem(contab); ++i){
+		ConDev *t = &contab[i];
+		if(t->probe(t) != 0 && t->pri > p->pri)
+			p = t;
+	}
+	if(p){
+		p->init(p);
+		con = p;
+	}
+}
 
 // https://wiki.osdev.org/BIOS
-void
+static void
 machdep(void)
 {
 	for(int i = 0; i < elem(probes); ++i){
@@ -61,8 +92,8 @@ done:
 void
 boot(int bootdev)
 {
-	machdep();	
 	print("\n\n===> Hello world <===\n\tBooted on disk 0x%x\n", bootdev);
+	machdep();	
 
 	for(;;){
 		char buf[8192];
diff --git a/boot/dat.h b/boot/dat.h
index 085d5ac..1166b5a 100644
--- a/boot/dat.h
+++ b/boot/dat.h
@@ -3,6 +3,12 @@
 // 0x64	Read	Status Register
 // 0x64	Write	Command Register
 
+enum{
+	CON_PC,
+	CON_SRI,
+	CON_END,
+};
+
 struct BIOSreg{
 	u32 ax; 
 	u32 cx; 
@@ -15,18 +21,21 @@ struct BIOSreg{
 	u32 es; 
 }__attribute__((packed));
 
-
 typedef struct{
 	char *name;
 	void (**probes)(void);
-	int cnt;
+	uint cnt;
 }BootProbe;
 
-typedef struct{
+typedef struct ConDev ConDev;
+struct ConDev{
+	int (*probe)(ConDev*);
+	void (*init)(ConDev *);
 	int (*getc)(int);
 	void (*putc)(int, int);
-	int	dev;
-}ConDev;
+	uint dev;
+	uchar pri; // the higher the better
+};
 
 // gdt.S
 extern volatile struct BIOSreg BIOSreg;
@@ -35,4 +44,5 @@ extern volatile struct BIOSreg BIOSreg;
 extern void (*probe1[])(void);
 extern void (*probe2[])(void);
 extern BootProbe probes[];
-extern ConDev condev;
\ No newline at end of file
+extern ConDev contab[CON_END];
+extern ConDev *con;
diff --git a/boot/fn.h b/boot/fn.h
index e997708..4d1bb47 100644
--- a/boot/fn.h
+++ b/boot/fn.h
@@ -1,7 +1,12 @@
-
 // console.c
+void cominit(ConDev *d);
+void pcinit(ConDev *d);
+int pcprobe(ConDev *d);
 int pcgetc(int dev);
 void pcputc(int dev, int c);
+int comprobe(ConDev *d);
+int comgetc(int dev);
+void computc(int dev, int c);
 
 // print.c
 void putchar(int c);
@@ -14,6 +19,26 @@ void a20up(void);
 // long.c
 long getsecs(void);
 
+static __inline int
+major(int x)
+{
+	return (x >> 8) & 0xff;
+}
+
+static __inline int
+minor(int x)
+{
+	return (x & 0xff) | ((x & 0xffff0000) >> 8);
+}
+
+static __inline int
+makedev(int x, int y)
+{
+	return (((x & 0xff) << 8) |
+		(y & 0xff) |
+		((y & 0xffff00)<<8));
+}
+
 static __inline void
 outb(int port, u8 data)
 {
diff --git a/boot/console.c b/boot/pccon.c
similarity index 72%
rename from boot/console.c
rename to boot/pccon.c
index 0f46609..5d41e48 100644
--- a/boot/console.c
+++ b/boot/pccon.c
@@ -1,7 +1,23 @@
+// PC console
 #include <u.h>
+#include "dat.h"
 #include "fn.h"
 
 // https://stanislavs.org/helppc/int_16.html
+int
+pcprobe(ConDev *d)
+{
+	d->pri = 2;
+	d->dev = makedev(12, 0);
+	print("PC:%d\n", minor(d->dev));
+	return 1;
+}
+
+void
+pcinit(ConDev *d)
+{
+	USED(d);	
+}
 
 void
 pcputc(int dev, int c)
@@ -23,4 +39,4 @@ pcgetc(int dev)
 	__asm volatile("int $0x36" : "=a" (rv) :
 	    "0" (0x000) : "%ecx", "%edx", "cc" );
 	return rv&0xff;
-}
\ No newline at end of file
+}
diff --git a/boot/print.c b/boot/print.c
index 857ff56..647e82d 100644
--- a/boot/print.c
+++ b/boot/print.c
@@ -15,7 +15,7 @@ print(const char *fmt, ...)
 {
 	va_list args;
 
-	va_start(args, fmt);	
+	va_start(args, fmt);
 	doprint(putchar, fmt, args);
 	va_end(args);
 }
@@ -31,7 +31,7 @@ doprint(void (*put)(int), const char *s, va_list ap)
 		++s;
 		switch(*s){
 		case 'd':
-			putint(put, va_arg(ap,int), "0123456789", 10);		
+			putint(put, va_arg(ap,int), "0123456789", 10);
 			break;
 		case 'x':
 			putint(put, va_arg(ap,int), "0123456789abcdef", 16);
@@ -45,7 +45,7 @@ doprint(void (*put)(int), const char *s, va_list ap)
 			break;
 		default:
 			return;
-		}	
+		}
 		++s;
 	}
 }
@@ -98,16 +98,16 @@ static void
 conputc(int c)
 {
 	if(c){
-		condev.putc(condev.dev, c);
+		con->putc(con->dev, c);
 		if(c == '\n')
-			condev.putc(condev.dev, '\r');
+			con->putc(con->dev, '\r');
 	}	
 }
 
 static int 
 congetc(void)
 {
-	return condev.getc(condev.dev);
+	return con->getc(con->dev);
 }
 
 static void
diff --git a/boot/sricon.c b/boot/sricon.c
new file mode 100644
index 0000000..fe37ce8
--- /dev/null
+++ b/boot/sricon.c
@@ -0,0 +1,185 @@
+// Serial console
+#include <u.h>
+#include "dat.h"
+#include "fn.h"
+
+/*
+ * 8250 UART and compatibles.
+ */
+enum {
+	Uart0		= 0x3F8,	/* COM1 */
+	Uart0IRQ	= 4,
+	Uart1		= 0x2F8,	/* COM2 */
+	Uart1IRQ 	= 3,
+	UartFREQ 	= 1843200,	/* 1.8432 MHz */
+};
+
+/* I/O ports */
+enum {
+	Rbr = 0, /* Receiver Buffer (RO) */
+	Thr = 0, /* Transmitter Holding (WO) */
+	Ier = 1, /* Interrupt Enable */
+	Iir = 2, /* Interrupt Identification (RO) */
+	Fcr = 2, /* FIFO Control (WO) */
+	Lcr = 3, /* Line Control */
+	Mcr = 4, /* Modem Control */
+	Lsr = 5, /* Line Status */
+	Msr = 6, /* Modem Status */
+	Scr = 7, /* Scratch Pad */
+	Dll = 0, /* Divisor Latch Low */
+	Dlh = 1, /* Divisor Latch High */
+};
+
+/* Interrupt Enable Registe */
+enum {			/* Ier */
+	Erda	= 0x01,	/* Enable Received Data Available */
+	Ethre	= 0x02,	/* Enable Thr Empty */
+	Erls	= 0x04,	/* Enable Receiver Line Status */
+	Ems	= 0x08,	/* Enable Modem Status */
+};
+
+/* Interrupt Identification Register */
+enum {			/* Iir */
+	Ims	= 0x00,	/* Ms interrupt */
+	Ip	= 0x01,	/* Interrupt Pending (not) */
+	Ithre	= 0x02,	/* Thr Empty */
+	Irda	= 0x04,	/* Received Data Available */
+	Irls	= 0x06,	/* Receiver Line Status */
+	Ictoi	= 0x0C,	/* Character Time-out Indication */
+	IirMASK	= 0x3F,
+	Ifena	= 0xC0,	/* FIFOs enabled */
+};
+
+/* FIFO Control Registe */
+enum {			/* Fcr */
+	FIFOena	= 0x01,	/* FIFO enable */
+	FIFOrclr= 0x02,	/* clear Rx FIFO */
+	FIFOtclr= 0x04,	/* clear Tx FIFO */
+	FIFO1	= 0x00,	/* Rx FIFO trigger level 1 byte */
+	FIFO4	= 0x40,	/* 4 bytes */
+	FIFO8	= 0x80,	/* 8 bytes */
+	FIFO14	= 0xC0,	/* 14 bytes */
+};
+
+/* Line Control Registe */
+enum {			/* Lcr */
+	Wls5	= 0x00,	/* Word Length Select 5 bits/byte */
+	Wls6	= 0x01,	/* 6 bits/byte */
+	Wls7	= 0x02,	/* 7 bits/byte */
+	Wls8	= 0x03,	/* 8 bits/byte */
+	WlsMASK	= 0x03,
+	Stb	= 0x04,	/* 2 stop bits */
+	Pen	= 0x08,	/* Parity Enable */
+	Eps	= 0x10,	/* Even Parity Select */
+	Stp	= 0x20,	/* Stick Parity */
+	Brk	= 0x40,	/* Break */
+	Dlab	= 0x80,	/* Divisor Latch Access Bit */
+};
+
+/* Modem Control Register */
+enum {			/* Mcr */
+	Dtr	= 0x01,	/* Data Terminal Ready */
+	Rts	= 0x02,	/* Ready To Send */
+	Out1	= 0x04,	/* no longer in use */
+	Ie	= 0x08,	/* IRQ Enable */
+	Dm	= 0x10,	/* Diagnostic Mode loopback */
+};
+
+/* Line Status Register */
+enum {			/* Lsr */
+	Dr	= 0x01,	/* Data Ready */
+	Oe	= 0x02,	/* Overrun Error */
+	Pe	= 0x04,	/* Parity Error */
+	Fe	= 0x08,	/* Framing Error */
+	Bi	= 0x10,	/* Break Interrupt */
+	Thre	= 0x20,	/* Thr Empty */
+	Temt	= 0x40,	/* Tramsmitter Empty */
+	FIFOerr	= 0x80,	/* error in receiver FIFO */
+};
+
+/* Modem Status Register */
+enum {			/* Msr */
+	Dcts	= 0x01,	/* Delta Cts */
+	Ddsr	= 0x02,	/* Delta Dsr */
+	Teri	= 0x04,	/* Trailing Edge of Ri */
+	Ddcd	= 0x08,	/* Delta Dcd */
+	Cts	= 0x10,	/* Clear To Send */
+	Dsr	= 0x20,	/* Data Set Ready */
+	Ri	= 0x40,	/* Ring Indicator */
+	Dcd	= 0x80,	/* Data Set Ready */
+};
+
+static int setbaud(int dev, int baud);
+
+// probe serial console
+// https://stanislavs.org/helppc/int_11.html
+// https://wiki.osdev.org/Serial_Ports
+int
+comprobe(ConDev *d)
+{
+	register int n;
+
+	__asm volatile("int $0x31" : "=a" (n):: "%ecx", "%edx", "cc");
+	n >>= 9;
+	n &= 0b111;
+	if(n == 0)
+		return 0;
+	for(int i = 0; i < n; ++i)
+		print("Found com %d\n", i);
+	d->pri = 0;	
+	d->dev = makedev(8, 0);
+	return n;
+}
+
+// init serial consone
+void
+cominit(ConDev *d)
+{
+	long t = getsecs() + 1;
+
+	outb(Uart0+Ier, 0);
+	setbaud(d->dev, 9600);
+	outb(Uart0+Mcr, Dtr|Rts);
+	outb(Uart0+Fcr, FIFOena|FIFOrclr|FIFOtclr|FIFO1);
+	inb(Uart0+Iir); // check fifo
+
+	// wait
+	for(ulong i = 1; ((i % 1000)!=0) && getsecs() < t; ++i)
+		;
+	// drain input buffer
+	while(inb(Uart0+Lsr) & Dr)
+		inb(Uart0+Rbr);
+}
+
+static int
+setbaud(int dev, int baud)
+{
+	int port = Uart0;
+	ulong div;
+
+	if(baud <= 0)
+		return -1;
+	/* Divisor = 115200/baud */
+	div = (UartFREQ+8*baud-1)/(16*baud);	
+	outb(port+Lcr, Dlab);
+	outb(port+Dlh, div>>8);
+	outb(port+Dll, div);
+	outb(port+Lcr, Wls8);
+	return 0;
+}
+
+int
+comgetc(int dev)
+{
+	while((inb(Uart0+Lsr) & Dr) == 0)
+		;
+	return inb(Uart0+Rbr) & 0xff;
+}
+
+void
+computc(int dev, int c)
+{
+	while((inb(Uart0+Lsr) & Thre) == 0)
+		;
+	outb(Uart0+Thr, c);	
+}
\ No newline at end of file
diff --git a/boot/time.c b/boot/time.c
index 377f8fb..8e3af65 100644
--- a/boot/time.c
+++ b/boot/time.c
@@ -3,8 +3,10 @@
 #include "fn.h"
 
 // https://stanislavs.org/helppc/int_1a.html
-#define INT_TIME 2<<8
-#define INT_DATE 4<<8
+enum{
+	GET_TIME = 2<<8,
+ 	GET_DATE = 4<<8,
+};
 
 static int
 bcd2int(u8 c)
@@ -59,8 +61,8 @@ getsecs(void)
 	u8 t[4], d[4];
 	long s;
 
-	int1a(INT_TIME, t);
-	int1a(INT_DATE, d);
+	int1a(GET_TIME, t);
+	int1a(GET_DATE, d);
 	s = (date2day(d[0]*100+d[1], d[2], d[3]) * 24 + t[0]) * 60
 		+ (t[1] * 60) + t[2];
 	return s;