diff --git a/src/emu/video/pc_vga.c b/src/emu/video/pc_vga.c
index c911f04d32b..6f8691ec5f3 100644
--- a/src/emu/video/pc_vga.c
+++ b/src/emu/video/pc_vga.c
@@ -5362,6 +5362,26 @@ WRITE16_MEMBER(mach8_device::mach8_linedraw_w)
 	logerror("ATI: Linedraw register write %04x, mode %i\n",data,mach8.linedraw);
 }
 
+READ16_MEMBER(mach8_device::mach8_sourcex_r)
+{
+	return ibm8514.dest_x;
+}
+
+READ16_MEMBER(mach8_device::mach8_sourcey_r)
+{
+	return ibm8514.dest_y;
+}
+
+WRITE16_MEMBER(mach8_device::mach8_ext_leftscissor_w)
+{
+	// TODO
+}
+
+WRITE16_MEMBER(mach8_device::mach8_ext_topscissor_w)
+{
+	// TODO
+}
+
 READ16_MEMBER(mach8_device::mach8_scratch0_r)
 {
 	return mach8.scratch0;
diff --git a/src/emu/video/pc_vga.h b/src/emu/video/pc_vga.h
index 478dd6c84f5..f615cd20f09 100644
--- a/src/emu/video/pc_vga.h
+++ b/src/emu/video/pc_vga.h
@@ -384,6 +384,10 @@ public:
 	WRITE16_MEMBER(mach8_scratch1_w);
 	READ16_MEMBER(mach8_config1_r);
 	READ16_MEMBER(mach8_config2_r);
+	READ16_MEMBER(mach8_sourcex_r);
+	READ16_MEMBER(mach8_sourcey_r);
+	WRITE16_MEMBER(mach8_ext_leftscissor_w);
+	WRITE16_MEMBER(mach8_ext_topscissor_w);
 protected:
 	virtual void device_start();
 	struct
diff --git a/src/mess/video/isa_vga_ati.c b/src/mess/video/isa_vga_ati.c
index 2abe6a34715..96b5d23a195 100644
--- a/src/mess/video/isa_vga_ati.c
+++ b/src/mess/video/isa_vga_ati.c
@@ -115,6 +115,8 @@ void isa16_vga_gfxultra_device::device_start()
 	m_isa->install16_device(0xbae8, 0xbaeb, 0, 0, read16_delegate(FUNC(mach8_device::ibm8514_foremix_r),m_8514), write16_delegate(FUNC(mach8_device::ibm8514_foremix_w),m_8514));
 	m_isa->install16_device(0xbee8, 0xbeeb, 0, 0, read16_delegate(FUNC(mach8_device::ibm8514_multifunc_r),m_8514), write16_delegate(FUNC(mach8_device::ibm8514_multifunc_w),m_8514));
 	m_isa->install16_device(0xe2e8, 0xe2eb, 0, 0, read16_delegate(FUNC(mach8_device::ibm8514_pixel_xfer_r),m_8514), write16_delegate(FUNC(mach8_device::ibm8514_pixel_xfer_w),m_8514));
+	m_isa->install16_device(0xdaec, 0xdaef, 0, 0, read16_delegate(FUNC(mach8_device::mach8_sourcex_r),m_8514), write16_delegate(FUNC(mach8_device::mach8_ext_leftscissor_w),m_8514));
+	m_isa->install16_device(0xdeec, 0xdeef, 0, 0, read16_delegate(FUNC(mach8_device::mach8_sourcey_r),m_8514), write16_delegate(FUNC(mach8_device::mach8_ext_topscissor_w),m_8514));
 	m_isa->install16_device(0xfeec, 0xfeef, 0, 0, read16_delegate(FUNC(mach8_device::mach8_linedraw_r),m_8514), write16_delegate(FUNC(mach8_device::mach8_linedraw_w),m_8514));
 
 	m_isa->install_memory(0xa0000, 0xbffff, 0, 0, read8_delegate(FUNC(ati_vga_device::mem_r),m_vga), write8_delegate(FUNC(ati_vga_device::mem_w),m_vga));