Broke out the ALi M5213 IDE from the ALi M1489 code (it turns out the ALi M1489 on-chip IDE is for all intents and purposes identical to the M5213) and made the Acer A1G use it.

src/machine/m_at_386dx_486.c

@@ -381,9 +381,9 @@ machine_at_acera1g_init(const machine_t *model)
         device_add(&gd5428_onboard_device);
 
     device_add(&keyboard_ps2_acer_pci_device);
-    device_add(&ide_vlb_2ch_device);
 
     device_add(&ali5105_device);
+    device_add(&ide_ali5213_device);
 
     return ret;
 }