diff --git a/src/devices/cpu/mips/r4000.cpp b/src/devices/cpu/mips/r4000.cpp
index 1970ba43cf3..1550655662e 100644
--- a/src/devices/cpu/mips/r4000.cpp
+++ b/src/devices/cpu/mips/r4000.cpp
@@ -3739,7 +3739,7 @@ void r4000_base_device::address_error(int intention, u64 const address)
 
 template <typename T> void r4000_base_device::accessors(T &m)
 {
-	space(AS_PROGRAM).cache(m);
+	space(AS_PROGRAM).specific(m);
 
 	read_byte = [&m](offs_t offset) { return m.read_byte(offset); };
 	read_word = [&m](offs_t offset) { return m.read_word(offset); };
diff --git a/src/devices/cpu/mips/r4000.h b/src/devices/cpu/mips/r4000.h
index f7e5b55e121..f905e520493 100644
--- a/src/devices/cpu/mips/r4000.h
+++ b/src/devices/cpu/mips/r4000.h
@@ -400,8 +400,8 @@ protected:
 	address_space_config m_program_config_be;
 
 	// memory access helpers
-	memory_access<36, 3, 0, ENDIANNESS_LITTLE>::cache m_le;
-	memory_access<36, 3, 0, ENDIANNESS_BIG>::cache m_be;
+	memory_access<32, 3, 0, ENDIANNESS_LITTLE>::specific m_le;
+	memory_access<32, 3, 0, ENDIANNESS_BIG>::specific m_be;
 
 	std::function<u8(offs_t offset)> read_byte;
 	std::function<u16(offs_t offset)> read_word;
diff --git a/src/mame/sgi/ip20.cpp b/src/mame/sgi/ip20.cpp
index d68cbd29c06..4066d7bac80 100644
--- a/src/mame/sgi/ip20.cpp
+++ b/src/mame/sgi/ip20.cpp
@@ -140,6 +140,10 @@ void ip20_state::cpu_map(address_map &map)
 	map(0x1fc0'0000, 0x1fc7'ffff).rom().region("prom", 0);
 }
 
+static DEVICE_INPUT_DEFAULTS_START(ip20_mc)
+	DEVICE_INPUT_DEFAULTS("VALID", 0x0f, 0x07)
+DEVICE_INPUT_DEFAULTS_END
+
 static void scsi_devices(device_slot_interface &device)
 {
 	device.option_add("cdrom", NSCSI_CDROM_SGI).machine_config(
@@ -172,6 +176,7 @@ void ip20_state::ip20(machine_config &config)
 
 	SGI_MC(config, m_mc, m_cpu, m_eerom, 50'000'000);
 	m_mc->eisa_present().set_constant(0);
+	m_mc->set_input_default(DEVICE_INPUT_DEFAULTS_NAME(ip20_mc));
 
 	SGI_HPC1(config, m_hpc, 0);
 	m_hpc->set_gio(m_cpu, AS_PROGRAM);
@@ -281,6 +286,10 @@ void ip20_state::ip20(machine_config &config)
 ROM_START(indigo_r4000)
 	ROM_REGION64_BE(0x80000, "prom", 0)
 	ROMX_LOAD("ip20prom.070-8116-004.bin", 0x000000, 0x080000, CRC(940d960e) SHA1(596aba530b53a147985ff3f6f853471ce48c866c), ROM_GROUPDWORD | ROM_REVERSE)
+
+	// hand-made content sets eaddr 08:00:69:12:34:56 and netaddr 192.168.137.2
+	ROM_REGION16_LE(0x100, "nvram", 0)
+	ROM_LOAD("nvram.bin", 0x000, 0x100, CRC(b8367798) SHA1(61af4c9dba69e9f0552c10770f16044421730b6d))
 ROM_END
 
 #define rom_indigo_r4400 rom_indigo_r4000
diff --git a/src/mame/sgi/ip6.cpp b/src/mame/sgi/ip6.cpp
index e7f0cf2da36..4183d195832 100644
--- a/src/mame/sgi/ip6.cpp
+++ b/src/mame/sgi/ip6.cpp
@@ -16,26 +16,38 @@
  *   - https://github.com/NetBSD/src/tree/trunk/sys/arch/sgimips/
  *
  * TODO:
- *   - audio, printer
- *   - devicify ioc1 and ctl1
- *
- * Status:
+ *  - audio, printer
+ *  - devicify ioc1 and ctl1
  *  - parity and cache diagnostics fail
- *  - irix 4.0.5 working
  *  - ide test failures
  *    - lca2 (unimplemented fpga program/readback)
  *    - nvram4 (security mode?)
  *    - fpu (cvt.?.? invalid operation exceptions)
  */
 
-/*
- * Installation instructions
- * --
- * 1. boot, enter monitor, set ethernet address: eaddr 08:00:69:12:34:56
- * 2. start mame with CDROM iso image as hard disk ID 6: mame 4d20 ... -scsi:6 harddisk -hard2 pathname.iso
- * 3. boot, enter monitor, launch sash: boot -f dksc(0,6,8)sash.IP6
- * 4.
- */
+ /*
+  * WIP
+  * --
+  * 4D/2x doesn't support CDROM, so to install IRIX, mount the .iso
+  * as if it's a hard disk: ... -scsi:6 harddisk -hard2 pathname.iso
+  *
+  * install IRIX 4.0.5/5.3:
+  *  - monitor: eaddr 08:00:69:12:34:56                         # set ethernet mac address
+  *  - monitor: init
+  *  - monitor: dksc(0,6,8)sash.IP6 dksc(0,6,7)stand/fx.IP6 -x  # start fx disk partition/label utility
+  *  - fx: r; ro; ..; l; sync; ..; exit                          # create root partition and label disk
+  *  - monitor: setenv tapedevice dksc(0,6,8)
+  *  - monitor: dksc(0,6,8)sash.IP6 -m                          # copy/boot from miniroot
+  *  - inst: sh                                                 # escape to shell from inst
+  *  - sh: mkdir /mnt; mount /dev/dsk/dks0d6s7 /mnt; exit       # mount distribution media
+  *  - inst: from /mnt/dist
+  *  - inst: go                                                 # may take ~1.5 hours
+  *  - inst: shroot
+  *  - sh: chkconfig windowsystem off; chkconfig xdm off            # disable graphics subsystems (until graphics works)
+  *  - sh: edit /etc/hosts and /etc/inittab                     # change host IP address, enable getty on console
+  *  - inst: quit                                               # complete installation and reboot
+  */
+
 
 #include "emu.h"