SIS_CFG_EDB_MASTER_EN indicates the EDB bus is used instead of
the PCI bus. When this bit is set, the Max DMA Burst Size
for TX/RX DMA should be no larger than 16 double words

Obtained from:	Linux driver source. (idea)

--- sys/pci/if_sisreg.h.orig	Sun Jan  5 01:29:53 2003
+++ sys/pci/if_sisreg.h	Sun Jan  5 01:38:08 2003
@@ -114,6 +114,7 @@
 #define SIS_CFG_OUTOFWIN_TIMER	0x00000020
 #define SIS_CFG_SINGLE_BACKOFF	0x00000040
 #define SIS_CFG_PCIREQ_ALG	0x00000080
+#define SIS_CFG_EDB_MASTER_EN	0x00002000
 
 #define SIS_EECTL_DIN		0x00000001
 #define SIS_EECTL_DOUT		0x00000002
@@ -259,8 +260,10 @@
 #define SIS_RXDMA_128BYTES	0x00600000
 #define SIS_RXDMA_256BYTES	0x00700000
 
-#define SIS_RXCFG \
+#define SIS_RXCFG256 \
 	(SIS_RXCFG_DRAIN(64)|SIS_RXDMA_256BYTES)
+#define SIS_RXCFG64 \
+	(SIS_RXCFG_DRAIN(64)|SIS_RXDMA_64BYTES)
 
 #define SIS_RXFILTCTL_ADDR	0x000F0000
 #define NS_RXFILTCTL_MCHASH	0x00200000
--- sys/pci/if_sis.c.orig	Sun Jan  5 01:23:52 2003
+++ sys/pci/if_sis.c	Sun Jan  5 01:45:26 2003
@@ -2014,8 +2014,16 @@
 	CSR_WRITE_4(sc, SIS_RX_LISTPTR, sc->sis_cdata.sis_rx_paddr);
 	CSR_WRITE_4(sc, SIS_TX_LISTPTR, sc->sis_cdata.sis_tx_paddr);
 
-	/* Set RX configuration */
-	CSR_WRITE_4(sc, SIS_RX_CFG, SIS_RXCFG);
+	/* SIS_CFG_EDB_MASTER_EN indicates the EDB bus is used instead of
+	 * the PCI bus. When this bit is set, the Max DMA Burst Size
+	 * for TX/RX DMA should be no larger than 16 double words.
+	 */
+	if (CSR_READ_4(sc, SIS_CFG) & SIS_CFG_EDB_MASTER_EN) {
+		CSR_WRITE_4(sc, SIS_RX_CFG, SIS_RXCFG64);
+	} else {
+		CSR_WRITE_4(sc, SIS_RX_CFG, SIS_RXCFG256);
+	}
+
 
 	/* Accept Long Packets for VLAN support */
 	SIS_SETBIT(sc, SIS_RX_CFG, SIS_RXCFG_RX_JABBER);