diff --git a/devicemodel/include/pci_core.h b/devicemodel/include/pci_core.h
index 711c5745a..cd7df1cde 100644
--- a/devicemodel/include/pci_core.h
+++ b/devicemodel/include/pci_core.h
@@ -45,8 +45,8 @@
 
 #define	PCI_EMUL_ECFG_BASE	0xE0000000UL	/* 3.5GB */
 
-#define	PCI_EMUL_MEMBASE64	0x100000000UL	/* 4GB */
-#define	PCI_EMUL_MEMLIMIT64	0x140000000UL	/* 5GB */
+#define	PCI_EMUL_MEMBASE64	0x4000000000UL	/* 256GB */
+#define	PCI_EMUL_MEMLIMIT64	0x8000000000UL	/* 512GB */
 
 #define SOFTWARE_SRAM_MAX_SIZE	0x00800000UL
 #define SOFTWARE_SRAM_BASE_GPA	(PCI_EMUL_MEMBASE32 - SOFTWARE_SRAM_MAX_SIZE)