diff --git a/hw/misc/aspeed_sdmc.c b/hw/misc/aspeed_sdmc.c
index 244e5c0dc5..1d28252377 100644
--- a/hw/misc/aspeed_sdmc.c
+++ b/hw/misc/aspeed_sdmc.c
@@ -192,7 +192,7 @@ static void aspeed_sdmc_reset(DeviceState *dev)
     case AST2400_A0_SILICON_REV:
         s->regs[R_CONF] |=
             ASPEED_SDMC_VGA_COMPAT |
-            ASPEED_SDMC_DRAM_SIZE(ast2400_rambits());
+            ASPEED_SDMC_DRAM_SIZE(s->ram_bits);
         break;
 
     case AST2500_A0_SILICON_REV:
@@ -200,7 +200,7 @@ static void aspeed_sdmc_reset(DeviceState *dev)
         s->regs[R_CONF] |=
             ASPEED_SDMC_HW_VERSION(1) |
             ASPEED_SDMC_VGA_APERTURE(ASPEED_SDMC_VGA_64MB) |
-            ASPEED_SDMC_DRAM_SIZE(ast2500_rambits());
+            ASPEED_SDMC_DRAM_SIZE(s->ram_bits);
         break;
 
     default:
@@ -219,6 +219,18 @@ static void aspeed_sdmc_realize(DeviceState *dev, Error **errp)
         return;
     }
 
+    switch (s->silicon_rev) {
+    case AST2400_A0_SILICON_REV:
+        s->ram_bits = ast2400_rambits();
+        break;
+    case AST2500_A0_SILICON_REV:
+    case AST2500_A1_SILICON_REV:
+        s->ram_bits = ast2500_rambits();
+        break;
+    default:
+        g_assert_not_reached();
+    }
+
     memory_region_init_io(&s->iomem, OBJECT(s), &aspeed_sdmc_ops, s,
                           TYPE_ASPEED_SDMC, 0x1000);
     sysbus_init_mmio(sbd, &s->iomem);
diff --git a/include/hw/misc/aspeed_sdmc.h b/include/hw/misc/aspeed_sdmc.h
index 7e081f6d2b..df7dce0edd 100644
--- a/include/hw/misc/aspeed_sdmc.h
+++ b/include/hw/misc/aspeed_sdmc.h
@@ -25,6 +25,7 @@ typedef struct AspeedSDMCState {
 
     uint32_t regs[ASPEED_SDMC_NR_REGS];
     uint32_t silicon_rev;
+    uint32_t ram_bits;
 
 } AspeedSDMCState;