Added Elonex PC-425X emulation.

src/mem.c

@@ -827,6 +827,23 @@ int loadbios()
                 fclose(f);
                 biosmask = 0x7fff;
                 return 1;
+                
+                case ROM_ELX_PC425X:
+                /*PC-425X uses a single ROM chip containing both main and video BIOSes.
+                  First 32kb is video BIOS, next 32kb is blank, last 64kb is main BIOS.
+                  Alternatively, seperate BIOS + video BIOS dumps are supported.*/
+                f = romfopen("elx_pc425x/elx_pc425x.bin", "rb");
+                if (!f)
+                {
+                        f = romfopen("elx_pc425x/elx_pc425x_bios.bin", "rb");
+                        if (!f)
+                                break;
+                }
+                else
+                        fseek(f, 0x10000, SEEK_SET);
+                romfread(rom, 65536, 1, f);
+                fclose(f);
+                return 1;
         }
         printf("Failed to load ROM!\n");
         if (f) fclose(f);