jamesbraid · Oct 30, 2026 · Oct 30, 2026 · Oct 30, 2026 · Oct 30, 2026 · Oct 30, 2026
diff --git a/CHANGELOG.md b/CHANGELOG.md
@@ -114,6 +114,65 @@ hashes are given where a change is easiest to understand by reading the commit.
   the cost follows what the guest wrote. Reflinking is unchanged. On Windows the
   copy is marked sparse first.
 
+### R10000 TLB widths
+
+- **Full 44-bit user addresses.** On the R10000 (Octane, IP28, and an O2 set to
+  `r10000`) EntryHi, the TLB match and the user-segment check keep VA bits 43:40;
+  they stopped at bit 39 before, so an address above 1 TiB took an Address Error.
+  The R4400 and R5000 are unchanged.
+- **FrameMask (CP0 register 21)** on the R10000 clears the EntryLo bits it
+  names, 33:18, on every TLB write, so a kernel that keeps software flags there
+  gets the physical address it meant. The register read as zero and ignored
+  writes before. The R4400 and R5000 have none.
+- **EntryLo** on the R10000 keeps its 28-bit PFN (bits 33:6, a 40-bit physical
+  address) and the uncached attribute in 63:62; it kept 30 bits before. The
+  attribute is stored and read back, not sent to the bus.
+- **TLB writes on the R10000** store zeros in the PFN bits below the page size,
+  so TLBR reads them back as zero, as the part does; on 16 KB pages that is
+  EntryLo bits 7:6. Translation is unchanged. The PROM's `ide` `tlb` test
+  failed 320 compares on this. The manual documents it for the R10000; the
+  R12000, R14000 and R16000 do the same as a model choice. The R4400 and
+  R5000 still keep the whole PFN.
+- **TLB refill vector on the R10000** follows the address space that missed:
+  a user address takes the XTLB vector only with UX set, xsseg with SX, and
+  kernel addresses with KX. A 64-bit kernel touching a 32-bit user address now
+  refills through 0x000, as the part does, not 0x080. The R4400 and R5000 still
+  choose by the current mode.
+
+### Refused uncached stores on the R10000 family
+
+- On the R10000 family (Octane, IP28, O2), an uncached store that nothing answers now
+  completes instead of raising a Data Bus Error, as the processor does. iris prints
+  "Unsupported uncached write ... (posted, completes)" for the first four such
+  stores and then at each power of two. Loads, instruction fetches, the R4400 and
+  the R5000 are unchanged.
+
+### Partial LWR on the R10000
+
+- On the R10000 (Octane, IP28, and an O2 with the R10000), an `LWR` that loads fewer
+  than four bytes now keeps bits 63:32 of the destination instead of sign-extending,
+  as the reference results for the part show. R4400 and R5000 machines are unchanged.
+  The JIT matches the interpreter, and the code-cache key changes only for the
+  machines that have the behaviour.
+
+### R10000 cache operations
+
+- **Index Load Data and Index Store Data** on the R10000's primary caches keep their
+  data (they read back zero before). The secondary cache's data slot is the address
+  shifted right by 3 instead of 4: one slot per doubleword.
+- **Secondary-cache tags** on the R10000 family read the reserved bits (TagLo 9, 12, 13 and
+  TagHi 30:4) as zero; the MRU bit and the other tag fields are kept.
+
+### R12000, R14000 and R16000
+
+- `[machine] cpu` and `--cpu` take `r12000`, `r14000`, `r16000` (revision 2.2,
+  the 800 MHz part) and `r16000_700` (revision 2.1, the 700 MHz part). The Octane
+  takes the R10000, R12000 and R14000 (defaulting to 195, 360 and 600 MHz), the
+  O2 the R5000, R10000 and R12000 (400 MHz for the R12000), the IP28 the R10000.
+  The R16000 has no machine yet; `iris-bench` is its only user. CP0 Config now
+  reports the part's own secondary-cache size, where every part read 1 MB, and
+  each R16000 presents its own reset word.
+
 ### `IRIS_GUI_GL` works in iris-gui
 
 - The GUI's GL capture path (`IRIS_GUI_GL=1`, or `[debug] gui_gl_capture`) never
@@ -203,6 +262,30 @@ hashes are given where a change is easiest to understand by reading the commit.
 - Memory past 4 GB is as fast as the rest: such a machine gets a 16 GB direct
   window, and the JIT compiles code anywhere in it.
 - A store-conditional on memory outside the window is now atomic with two CPUs.
+### SGI Fuel (IP34 board, IP35 software platform)
+
+- **The Fuel takes a VPro board**: `[graphics] board = "v12"` or `"v10"`
+  fits the Octane's VPro model at crossbar widget 13. IRIX 6.5.30 with the
+  VPro driver brings the X login screen up on it.
+
+- Added a headless Fuel profile with the 500 MHz R14000, 512 MiB RAM,
+  Bedrock, dual-head XBridge, IOC3 networking and two-channel ISP12160 SCSI.
+  The normal interpreter boot reaches the IRIX 6.5.30 root shell with PROM
+  6.210. See the [Fuel guide](docs/fuel-ip34.md).
+- **jitv2 compiles uncached code from the uncached view.** The PROM runs from the
+  reset window uncached; once memory covers that window the cached view returns
+  RAM there, and the compile pool used to compile RAM's bytes in place of the
+  PROM's. An uncached fetch now keys a code page of its own and is compiled and
+  invalidated through the view the CPU fetched it by. Other machines are
+  unchanged.
+
+### PCI configuration
+
+- A PCI function can describe its own writable header fields and
+  write-one-to-clear status bits. Byte and halfword configuration writes
+  through a Bridge carry their byte enables, so such a function keeps the
+  status events a narrow write did not select. No Octane function has
+  write-one-to-clear status bits, so the Octane behaves as before.
 
 ### VNC, and screen and pointer commands
 
@@ -513,6 +596,9 @@ hashes are given where a change is easiest to understand by reading the commit.
 
 ### SGI O2 (IP32)
 
+- **The O2's memory alias holds for pages with high PTE bits set.** A mapped page
+  whose address had a bit set above bit 31 missed the alias of RAM at
+  0x8000_0000 and reached the PCI window instead.
 - **The O2 runs on the shadow cache from reset.** The full cache model, and
   the switch to and from it during POST and reboots, are gone
   (`src/ip32_handover.rs`), and with them a branch on every cached load, store

diff --git a/FEATURES.md b/FEATURES.md
@@ -170,15 +170,34 @@ the first `[section]`, because TOML tables continue until the next header.
 
 | Key | Default | Values and behavior |
 |---|---|---|
-| `machine.profile` | `indy_ip24` | indy_ip24, indigo2_ip22, indigo2_ip28, o2_ip32 (configured by `[o2]`, see [the O2 guide](docs/o2-ip32.md)), octane_ip30 (configured by `[octane]`, see [the Octane guide](docs/octane-ip30.md)). |
-| `machine.cpu` | `r4400` | r4400, r5000, r10000; CPU/ISA choice is independent of build features. An O2 takes r5000 or r10000 (an r4400 is refused when the machine is built); the Octane is r10000 only. |
+| `machine.profile` | `indy_ip24` | indy_ip24, indigo2_ip22, indigo2_ip28, o2_ip32 (configured by `[o2]`, see [the O2 guide](docs/o2-ip32.md)), octane_ip30 (configured by `[octane]`, see [the Octane guide](docs/octane-ip30.md)), fuel_ip34 (see [the Fuel guide](docs/fuel-ip34.md)). |
+| `machine.cpu` | `r4400` | r4400, r5000, r10000, r12000 (Octane, O2), r14000 (Octane, Fuel), r16000 (no machine yet). CPU/ISA choice is independent of build features. A Fuel always runs its one R14000: set `r14000` (`r10000`, the family, is also accepted); any other value is refused. |
 | `machine.cpus` | `1` | Processors fitted. 2 only on the Octane; see [its guide](docs/Octane/multiprocessor.md). |
 
+### [fuel]
+
+Fuel-specific settings apply when `machine.profile = "fuel_ip34"`.
+
+| Key | Default | Values and behavior |
+|---|---|---|
+| `flash` | unset | Persistent 16 MiB boot-flash file. Unset, the flash is volatile. |
+| `console` | `l1` | `l1`, `ioc3a` or `ioc3b`. Selects the guest console connection. |
+| `l1_port` | `8882` | Host TCP port for the L1 console. Used when `console = "l1"`. |
+| `l1_log` | unset | Optional serial log path for L1 output when an IOC3 port is selected as console. |
+| `l1_revision` | `1.48.1` | L1 firmware revision as `major.minor.patch`, decimal. The guest reads it with L1 request `0x0005`. |
+| `brick_serial` | `EMUN00` | L1 brick serial, at most 37 bytes. The guest reads it with L1 request `0x0004`. The default is a marked synthetic serial, not a real one. |
+
+The machine uses one 500 MHz R14000 and fixed 512 MiB RAM in two 256 MiB
+banks. Its IOC3 has no keyboard or mouse ports, so it runs on a serial
+console. A `[fuel]` table is written to a saved config only when one of
+these keys is set. The sample configuration and supported PROM inputs are in the
+[Fuel guide](docs/fuel-ip34.md).
+
 ### [graphics]
 
 | Key | Default | Values and behavior |
 |---|---|---|
-| `graphics.board` | `newport`; `solidimpact` on the Octane | newport, xz, extreme, solidimpact, highimpact, maximpact, v6, v8, v10, v12, none. Extreme is Indigo2 only. The Octane takes only `solidimpact` (SI), `highimpact` (SI with texture option), `maximpact` (MXI), `v6`, `v8`, `v10`, `v12` (the VPro boards, also `vpro:v12` and so on; need an IRIX install with the VPro driver, IRIX 6.5.10 or later and PROM 4.0, or 4.5 for the V10 and V12, which shipped only in the Octane2 and so give the machine the Octane2's Crossbow 1.4 and Bridge revision) or `none` (no board: the machine runs on its serial console, with no window). |
+| `graphics.board` | `newport`; `solidimpact` on the Octane | newport, xz, extreme, solidimpact, highimpact, maximpact, v6, v8, v10, v12, none. Extreme is Indigo2 only. The Octane takes only `solidimpact` (SI), `highimpact` (SI with texture option), `maximpact` (MXI), `v6`, `v8`, `v10`, `v12` (the VPro boards, also `vpro:v12` and so on; need an IRIX install with the VPro driver, IRIX 6.5.10 or later and PROM 4.0, or 4.5 for the V10 and V12, which shipped only in the Octane2 and so give the machine the Octane2's Crossbow 1.4 and Bridge revision) or `none` (no board: the machine runs on its serial console, with no window). The Fuel takes `v12` or `v10` in its graphics slot, or `none`, its default. |
 | `graphics.heads` | `1` | 1 or 2; dual-head requires Newport. |
 | `graphics.resolution` | `guest` | guest, 1024x768, 1280x960, 1280x1024; presets require Newport. |
 
@@ -209,7 +228,7 @@ An explicit non-disk kind takes precedence over the legacy cdrom flag.
 
 | Key | Default | Values and behavior |
 |---|---|---|
-| `network.mode` | `nat` | nat, pcap, stream or off (no Ethernet; O2 and Octane only). Stream needs `network.stream`. PCAP needs build support and host capture permissions. PCAP works on every Ethernet; stream on every onboard one, not on a DaynaPort. |
+| `network.mode` | `nat` | nat, pcap, stream or off (no Ethernet; O2, Octane and Fuel only). Stream needs `network.stream`. PCAP needs build support and host capture permissions. PCAP works on every Ethernet; stream on every onboard one, not on a DaynaPort. |
 | `network.stream` | `unset` | `tcp:IP:PORT` or `unix:PATH`: the server of the private segment for `mode = "stream"` (QEMU `-netdev stream` framing). See NETWORKING.md. |
 | `network.pcap_interface` | `auto-pick when unset` | Interface name or numeric list index; PCAP only. |
 | `network.nfs_pcap_ip` | `unset` | Virtual LAN IP for the built-in NFS responder in PCAP mode. |
@@ -373,8 +392,8 @@ IP22/IP24 four-bank IRIX 6.5 behavior remains separate from IP28's verified
 two-bank 1 GB layout. Extreme requires IP22. All non-Newport boards require
 `heads=1` and `resolution="guest"`. IP28 IRIX needs IMPACT; its PROM has an
 embedded fallback.
-The config validator permits SCSI controller 1 only on IP22, the O2 and the
-Octane, the machines with two controllers.
+The config validator permits SCSI controller 1 only on IP22, the O2, Octane
+and Fuel. These machines have two controllers.
 
 Standalone CLI options update the loaded config where supplied; boolean enable
 switches do not provide a general way to clear every saved true setting.
@@ -427,7 +446,7 @@ iris-gui does not parse this standalone option set; use its named-machine UI.
 | `--list-net-interfaces` | Print the host network interfaces libpcap can bridge onto, then exit. Requires a build with --features pcap. |
 | `--no-scsi-deferred-int` | Disable deferred SCSI status interrupts (default: enabled for OpenBSD/NetBSD compatibility). |
 | `--cpu` | Emulated CPU: `r4400` (default), `r5000`, or `r10000`. Overrides `[machine] cpu`.  |
-| `--graphics` | Graphics board: `newport` (default), `xz`, `extreme`, `solidimpact`, `highimpact`, `maximpact` (or `impact:solid`, `impact:high`, `impact:max`), `v6`, `v8`, `v10`, `v12` (`vpro:v12` and so on, Octane only). |
+| `--graphics` | Graphics board: `newport` (default), `xz`, `extreme`, `solidimpact`, `highimpact`, `maximpact` (or `impact:solid`, `impact:high`, `impact:max`), `v6`, `v8`, `v10`, `v12` (`vpro:v12` and so on; Octane, and `v10`/`v12` on the Fuel). |
 | `--gdb-port` | Enable GDB stub on the given TCP port (e.g. --gdb-port 1234). Connect with: target remote localhost:<port> |
 | `--monitor-port` | Monitor console port on 127.0.0.1 (default 8888). Give each iris running at once its own. |
 | `--vnc [ADDR]` | Serve the screen, keyboard and mouse over VNC on ADDR (`host:port` or a port; default 127.0.0.1:5900). Sets `vnc.listen`. |