Note: this is the third version of this patch.

Apply by doing
       cd /usr/src/sys/arch/sparc/dev
       patch -p0 < hme.patch

And then rebuild your kernel.

Index: sbus.c
===================================================================
RCS file: /cvs/src/sys/arch/sparc/dev/sbus.c,v
retrieving revision 1.6
retrieving revision 1.7
diff -u -r1.6 -r1.7
--- sbus.c      1998/11/11 00:26:00     1.6
+++ sbus.c      1998/12/14 17:51:35     1.7
@@ -1,4 +1,4 @@
-/*     $OpenBSD: sbus.c,v 1.6 1998/11/11 00:26:00 jason Exp $  */
+/*     $OpenBSD: sbus.c,v 1.7 1998/12/14 17:51:35 deraadt Exp $        */
/*     $NetBSD: sbus.c,v 1.17 1997/06/01 22:10:39 pk Exp $ */

/*
@@ -59,6 +59,7 @@

#include <sparc/dev/sbusreg.h>
#include <sparc/dev/sbusvar.h>
+#include <sparc/dev/dmareg.h>

int sbus_print __P((void *, const char *));
void sbusreset __P((int));
@@ -151,6 +152,7 @@
        * Get the SBus burst transfer size if burst transfers are supported
        */
       sc->sc_burst = getpropint(node, "burst-sizes", 0);
+       sc->sc_burst = sc->sc_burst & ~SBUS_BURST_64;

       if (ra->ra_bp != NULL && strcmp(ra->ra_bp->name, "sbus") == 0)
               oca.ca_ra.ra_bp = ra->ra_bp + 1;
Index: hme.c
===================================================================
RCS file: /cvs/src/sys/arch/sparc/dev/hme.c,v
retrieving revision 1.13
retrieving revision 1.14
diff -u -r1.13 -r1.14
--- hme.c       1998/11/11 00:26:00     1.13
+++ hme.c       1998/12/14 17:37:24     1.14
@@ -1,4 +1,4 @@
-/*     $OpenBSD: hme.c,v 1.13 1998/11/11 00:26:00 jason Exp $  */
+/*     $OpenBSD: hme.c,v 1.14 1998/12/14 17:37:24 jason Exp $  */

/*
 * Copyright (c) 1998 Jason L. Wright ([email protected])
@@ -196,7 +196,12 @@
       else if (sc->sc_rev != 0xa0)
               sc->sc_flags = HME_FLAG_NOT_A0;

-       sc->sc_burst = ((struct sbus_softc *)parent)->sc_burst;
+       sc->sc_burst = getpropint(ca->ca_ra.ra_node, "burst-sizes", -1);
+       if (sc->sc_burst == -1)
+               sc->sc_burst = ((struct sbus_softc *)parent)->sc_burst;
+
+        /* Clamp at parent's burst sizes */
+       sc->sc_burst &= ((struct sbus_softc *)parent)->sc_burst;

       hme_meminit(sc);