diff --git a/src/include/86box/smbus.h b/src/include/86box/smbus.h
index 058b70ffc..6923a7edb 100644
--- a/src/include/86box/smbus.h
+++ b/src/include/86box/smbus.h
@@ -24,7 +24,7 @@ extern void	smbus_sethandler(uint8_t base, int size,
     			uint8_t (*read_byte)(uint8_t addr, void *priv),
     			uint8_t (*read_byte_cmd)(uint8_t addr, uint8_t cmd, void *priv),
     			uint16_t (*read_word_cmd)(uint8_t addr, uint8_t cmd, void *priv),
-    			uint8_t (*read_block_cmd)(uint8_t addr, uint8_t cmd, uint8_t *data, void *priv),
+    			uint8_t (*read_block_cmd)(uint8_t addr, uint8_t cmd, uint8_t *data, uint8_t len, void *priv),
     			void (*write_byte)(uint8_t addr, uint8_t val, void *priv),
     			void (*write_byte_cmd)(uint8_t addr, uint8_t cmd, uint8_t val, void *priv),
     			void (*write_word_cmd)(uint8_t addr, uint8_t cmd, uint16_t val, void *priv),
@@ -35,7 +35,7 @@ extern void	smbus_removehandler(uint8_t base, int size,
     			uint8_t (*read_byte)(uint8_t addr, void *priv),
     			uint8_t (*read_byte_cmd)(uint8_t addr, uint8_t cmd, void *priv),
     			uint16_t (*read_word_cmd)(uint8_t addr, uint8_t cmd, void *priv),
-    			uint8_t (*read_block_cmd)(uint8_t addr, uint8_t cmd, uint8_t *data, void *priv),
+    			uint8_t (*read_block_cmd)(uint8_t addr, uint8_t cmd, uint8_t *data, uint8_t len, void *priv),
     			void (*write_byte)(uint8_t addr, uint8_t val, void *priv),
     			void (*write_byte_cmd)(uint8_t addr, uint8_t cmd, uint8_t val, void *priv),
     			void (*write_word_cmd)(uint8_t addr, uint8_t cmd, uint16_t val, void *priv),
@@ -46,7 +46,7 @@ extern void	smbus_handler(int set, uint8_t base, int size,
     			uint8_t (*read_byte)(uint8_t addr, void *priv),
     			uint8_t (*read_byte_cmd)(uint8_t addr, uint8_t cmd, void *priv),
     			uint16_t (*read_word_cmd)(uint8_t addr, uint8_t cmd, void *priv),
-    			uint8_t (*read_block_cmd)(uint8_t addr, uint8_t cmd, uint8_t *data, void *priv),
+    			uint8_t (*read_block_cmd)(uint8_t addr, uint8_t cmd, uint8_t *data, uint8_t len, void *priv),
     			void (*write_byte)(uint8_t addr, uint8_t val, void *priv),
     			void (*write_byte_cmd)(uint8_t addr, uint8_t cmd, uint8_t val, void *priv),
     			void (*write_word_cmd)(uint8_t addr, uint8_t cmd, uint16_t val, void *priv),
@@ -57,7 +57,7 @@ extern uint8_t	smbus_has_device(uint8_t addr);
 extern uint8_t	smbus_read_byte(uint8_t addr);
 extern uint8_t	smbus_read_byte_cmd(uint8_t addr, uint8_t cmd);
 extern uint16_t	smbus_read_word_cmd(uint8_t addr, uint8_t cmd);
-extern uint8_t	smbus_read_block_cmd(uint8_t addr, uint8_t cmd, uint8_t *data);
+extern uint8_t	smbus_read_block_cmd(uint8_t addr, uint8_t cmd, uint8_t *data, uint8_t len);
 extern void	smbus_write_byte(uint8_t addr, uint8_t val);
 extern void	smbus_write_byte_cmd(uint8_t addr, uint8_t cmd, uint8_t val);
 extern void	smbus_write_word_cmd(uint8_t addr, uint8_t cmd, uint16_t val);
diff --git a/src/smbus.c b/src/smbus.c
index d24435cc7..fdb98ea78 100644
--- a/src/smbus.c
+++ b/src/smbus.c
@@ -33,7 +33,7 @@ typedef struct _smbus_ {
     	uint8_t  (*read_byte)(uint8_t addr, void *priv);
     	uint8_t  (*read_byte_cmd)(uint8_t addr, uint8_t cmd, void *priv);
     	uint16_t (*read_word_cmd)(uint8_t addr, uint8_t cmd, void *priv);
-    	uint8_t  (*read_block_cmd)(uint8_t addr, uint8_t cmd, uint8_t *data, void *priv);
+    	uint8_t  (*read_block_cmd)(uint8_t addr, uint8_t cmd, uint8_t *data, uint8_t len, void *priv);
 
     	void	 (*write_byte)(uint8_t addr, uint8_t val, void *priv);
     	void	 (*write_byte_cmd)(uint8_t addr, uint8_t cmd, uint8_t val, void *priv);
@@ -73,7 +73,7 @@ smbus_log(const char *fmt, ...)
 static uint8_t smbus_null_read_byte(uint8_t addr, void *priv) { smbus_log("SMBus: read_byte(%02x)\n", addr); return(0xff); }
 static uint8_t smbus_null_read_byte_cmd(uint8_t addr, uint8_t cmd, void *priv) { smbus_log("SMBus: read_byte_cmd(%02x, %02x)\n", addr, cmd); return(0xff); }
 static uint16_t smbus_null_read_word_cmd(uint8_t addr, uint8_t cmd, void *priv) { smbus_log("SMBus: read_word_cmd(%02x, %02x)\n", addr, cmd); return(0xffff); }
-static uint8_t smbus_null_read_block_cmd(uint8_t addr, uint8_t cmd, uint8_t *data, void *priv) { smbus_log("SMBus: read_block_cmd(%02x, %02x)\n", addr, cmd); return(0x00); };
+static uint8_t smbus_null_read_block_cmd(uint8_t addr, uint8_t cmd, uint8_t *data, uint8_t len, void *priv) { smbus_log("SMBus: read_block_cmd(%02x, %02x)\n", addr, cmd); return(0x00); };
 static void smbus_null_write_byte(uint8_t addr, uint8_t val, void *priv) { smbus_log("SMBus: write_byte(%02x, %02x)\n", addr, val); }
 static void smbus_null_write_byte_cmd(uint8_t addr, uint8_t cmd, uint8_t val, void *priv) { smbus_log("SMBus: write_byte_cmd(%02x, %02x, %02x)\n", addr, cmd, val); }
 static void smbus_null_write_word_cmd(uint8_t addr, uint8_t cmd, uint16_t val, void *priv) { smbus_log("SMBus: write_word_cmd(%02x, %02x, %04x)\n", addr, cmd, val); }
@@ -135,7 +135,7 @@ smbus_sethandler(uint8_t base, int size,
     		 uint8_t (*read_byte)(uint8_t addr, void *priv),
     		 uint8_t (*read_byte_cmd)(uint8_t addr, uint8_t cmd, void *priv),
     		 uint16_t (*read_word_cmd)(uint8_t addr, uint8_t cmd, void *priv),
-    		 uint8_t (*read_block_cmd)(uint8_t addr, uint8_t cmd, uint8_t *data, void *priv),
+    		 uint8_t (*read_block_cmd)(uint8_t addr, uint8_t cmd, uint8_t *data, uint8_t len, void *priv),
     		 void (*write_byte)(uint8_t addr, uint8_t val, void *priv),
     		 void (*write_byte_cmd)(uint8_t addr, uint8_t cmd, uint8_t val, void *priv),
     		 void (*write_word_cmd)(uint8_t addr, uint8_t cmd, uint16_t val, void *priv),
@@ -180,7 +180,7 @@ smbus_removehandler(uint8_t base, int size,
     		    uint8_t (*read_byte)(uint8_t addr, void *priv),
     		    uint8_t (*read_byte_cmd)(uint8_t addr, uint8_t cmd, void *priv),
     		    uint16_t (*read_word_cmd)(uint8_t addr, uint8_t cmd, void *priv),
-    		    uint8_t (*read_block_cmd)(uint8_t addr, uint8_t cmd, uint8_t *data, void *priv),
+    		    uint8_t (*read_block_cmd)(uint8_t addr, uint8_t cmd, uint8_t *data, uint8_t len, void *priv),
     		    void (*write_byte)(uint8_t addr, uint8_t val, void *priv),
     		    void (*write_byte_cmd)(uint8_t addr, uint8_t cmd, uint8_t val, void *priv),
     		    void (*write_word_cmd)(uint8_t addr, uint8_t cmd, uint16_t val, void *priv),
@@ -223,7 +223,7 @@ smbus_handler(int set, uint8_t base, int size,
     	      uint8_t (*read_byte)(uint8_t addr, void *priv),
     	      uint8_t (*read_byte_cmd)(uint8_t addr, uint8_t cmd, void *priv),
     	      uint16_t (*read_word_cmd)(uint8_t addr, uint8_t cmd, void *priv),
-    	      uint8_t (*read_block_cmd)(uint8_t addr, uint8_t cmd, uint8_t *data, void *priv),
+    	      uint8_t (*read_block_cmd)(uint8_t addr, uint8_t cmd, uint8_t *data, uint8_t len, void *priv),
     	      void (*write_byte)(uint8_t addr, uint8_t val, void *priv),
     	      void (*write_byte_cmd)(uint8_t addr, uint8_t cmd, uint8_t val, void *priv),
     	      void (*write_word_cmd)(uint8_t addr, uint8_t cmd, uint16_t val, void *priv),
@@ -308,7 +308,7 @@ smbus_read_word_cmd(uint8_t addr, uint8_t cmd)
 }
 
 uint8_t
-smbus_read_block_cmd(uint8_t addr, uint8_t cmd, uint8_t *data)
+smbus_read_block_cmd(uint8_t addr, uint8_t cmd, uint8_t *data, uint8_t len)
 {
     uint8_t ret = 0;
     smbus_t *p;
@@ -318,7 +318,7 @@ smbus_read_block_cmd(uint8_t addr, uint8_t cmd, uint8_t *data)
     if (p) {
     	while(p) {
     		if (p->read_block_cmd) {
-    			ret = MAX(ret, p->read_block_cmd(addr, cmd, data, p->priv));
+    			ret = MAX(ret, p->read_block_cmd(addr, cmd, data, len, p->priv));
     			found++;
     		}
     		p = p->next;
diff --git a/src/smbus_piix4.c b/src/smbus_piix4.c
index 8a1a0a762..ad8ff64d0 100644
--- a/src/smbus_piix4.c
+++ b/src/smbus_piix4.c
@@ -157,7 +157,7 @@ smbus_piix4_write(uint16_t addr, uint8_t val, void *priv)
     					break;
     				case 0x5: /* block R/W */
     					if (smbus_read)
-    						dev->data0 = smbus_read_block_cmd(smbus_addr, dev->cmd, dev->data);
+    						dev->data0 = smbus_read_block_cmd(smbus_addr, dev->cmd, dev->data, SMBUS_PIIX4_BLOCK_DATA_SIZE);
     					else
     						smbus_write_block_cmd(smbus_addr, dev->cmd, dev->data, dev->data0);
     					dev->next_stat = 0x2;