diff --git a/src/chipset/via_pipc.c b/src/chipset/via_pipc.c
index f62775dc7..5b86c8d59 100644
--- a/src/chipset/via_pipc.c
+++ b/src/chipset/via_pipc.c
@@ -1122,9 +1122,8 @@ pipc_write(int func, int addr, uint8_t val, void *priv)
 			break;
 
 		case 0x42:
-			dev->power_regs[addr] &= ~0x2f;
-			dev->power_regs[addr] |= val & 0x2f;
-			acpi_set_irq_line(dev->acpi, dev->power_regs[addr]);
+			dev->power_regs[addr] = (dev->power_regs[addr] & 0xf0) | (val & 0x0f);
+			acpi_set_irq_line(dev->acpi, dev->power_regs[addr] & 0x0f);
 			break;
 
 		case 0x54:
diff --git a/src/nvr_at.c b/src/nvr_at.c
index bf188dbbf..ff1c6fcb0 100644
--- a/src/nvr_at.c
+++ b/src/nvr_at.c
@@ -589,6 +589,9 @@ nvr_reg_write(uint16_t reg, uint8_t val, void *priv)
 		break;
 
 	case RTC_REGD:		/* R/O */
+		/* This is needed for VIA, where writing to this register changes a write-only
+		   bit whose value is read from power management register 42. */
+		nvr->regs[RTC_REGD] = val & 0x80;
 		break;
 
 	case 0x2e:
@@ -796,6 +799,8 @@ nvr_reset(nvr_t *nvr)
     nvr->regs[RTC_YEAR] = RTC_BCD(80);
     if (local->cent != 0xFF)
 	nvr->regs[local->cent] = RTC_BCD(19);
+
+    nvr->regs[RTC_REGD] = REGD_VRT;
 }
 
 /* Process after loading from file. */