sayuri: Update documentation

machines/sayuri/README.md

@@ -4,17 +4,92 @@
 
 HP Z440 workstation.
 
- * [Intel Xeon E5-1620 v4](https://ark.intel.com/content/www/us/en/ark/products/92991/intel-xeon-processor-e5-1620-v4-10m-cache-3-50-ghz.html)
+ * [Intel Xeon E5-2683 v4](https://ark.intel.com/content/www/us/en/ark/products/91766/intel-xeon-processor-e52683-v4-40m-cache-2-10-ghz.html)
- * 16 GiB DDR4 2400 MHz ECC memory
+ * 4×4 GiB DDR4 2400 MHz ECC memory
  * 250GB Samsung 970 Evo Pro NVMe SSD
- * 256GB micron SSD
+ * 256GB micron MTFDDAK256TBN-1AR15ABHA SATA SSD
  * 2TB Toshiba HDWA120 HDD
- * Sapphire Nitro+ Radeon RX 480
+ * Sapphire Nitro+ Radeon RX 480 (8 GiB VRAM)
+
+### Mods
+
+#### Fan
+
+The original fans are really loud if you run them at a higher speed.
+What fans are used depend on the exact model of the Z440,
+mine had a Delta QUR0912VH as rear case fan,
+a Delta AFB0912VH as front fan
+and a Foxconn PVA092G12S as CPU fan.
+Since the firmware only allows dynamic fan control via Intel QST,
+which is not supported in the kernel,
+the “minimum fan speed” set in the firmware configuration is always used.
+I replaced all three fans (rear case fan, front “PCIe” fan, CPU fan) with aftermarket products.
+For the rear case fan and CPU fan I used Noctua NF-A9 PWM fans,
+for the front fan an Arctic F9 PWM (for the sole reason that it is cheaper).
+Since HP decided to use different connectors for all of the fans
+(with the CPU fan connector having a proprietary 6-pin connector),
+I had to get creative with plugging them in.
+One alternative suggested by Michael Stapelberg in [his article on fan replacement in a HP Z440](https://michael.stapelberg.ch/posts/2021-08-28-silent-hp-z440-workstation/)
+is to remove the guard rails of the fans.
+Since this is destructive and I might want to sell the fans again if I don’t use them anymore,
+I decided against this
+and instead opted for connecting them manually with cheap jumper cables.
+This certainly is not the prettiest solution, but it works.
+As for the CPU fan,
+the fifth and sixth wire are actually not needed
+and a 4-pin PWM fan can be plugged into the connector (with jumpers).
+
+#### CPU
+
+The original CPU that came in my model was an Intel Xeon E5-1620 v4 CPU
+with 4 cores (8 threads),
+a base clock speed of 3.5 GHz
+and a boost clock speed of 3.8 GHz.
+To achieve better multicore performance,
+I upgraded it to an Intel Xeon E5-2683 v4, which can be found used for semi-cheap on AliExpress.
+It has 16 cores (32 threads),
+a base clock speed of 2.1 GHz
+and a boost clock speed of 3 GHz.
+While the CPU worked out-of-the box with the 2020 firmware revision I had on it,
+it did not offer frequency control in linux (and therefore stayed at its base clock).
+Upgrading to the newest firmware did not fix this issue.
+A workaround is to enable CPU HWPM in the firmware,
+which strips the kernel from frequency control and instead hands it to the firmware,
+which at least allows the CPU to reach 2.7 GHz
+Since this setting makes it impossible to determine the CPU clock via `cpupower frequency-info`,
+they have to be obtained by running `grep -E '^cpu MHz' /proc/cpuinfo` (one line for every thread).
+
+However, all CPUs compatible with the socket of this system (2011-3) share the same problem:
+They suffer from many security vulnerabilities,
+the mitigation of which slows them down massively.
+A possible workaround is to disable mitigations (https://make-linux-fast-again.com/),
+which, however, makes the CPU vulnerable to all those attacks again!
+This is implemented by the `yolo` specialisation,
+which can be selected at boot.
+
+The result of this is that,
+while it has double the cores and is a desktop/server CPU,
+it still is around 15 % slower (!) than my laptop’s Ryzen 7 5850U in multithreaded synthetic workloads.
+It looks even worse in single-threaded workloads,
+in which my laptop is five times as fast.
+
+#### Memory
+
+I have not yet upgraded the memory for cost reasons.
+It still is the original 4 sticks of Hynix HMA451R7AFR8N-UH (4 GiB DDR4 2400 MHz ECC).
+An upgrade is necessary due to many processes’ memory usage scaling linearily with CPU cores,
+the prime example being compiling with `make -j32` et al.
+
+#### Conclusion
+
+Is it worth it?
+Probably not, especially as a desktop machine.
+It might come in handy at a later time as a server.
 
 ## Purpose
 
-Tasks that benefit from parallel computing, require a decent amount of GPU
+Tasks that require a decent amount of GPU power
-power or possibly even both.
+and/or have to run while I do other things (on my laptop).
 
 ## Name
 

machines/sayuri/configuration.nix

@@ -75,7 +75,7 @@
         user = "sbruder";
       };
     };
-    intel-sucks.configuration = {
+    yolo.configuration = {
       # https://make-linux-fast-again.com/
       boot.kernelParams = [
         "l1tf=off"