Clarify SMs/CUs/EUs belonging to nVidia/AMD/Intel. (#374)

* Clarify SMs/CUs/EUs belonging to nVidia/AMD/Intel.
  Also add a line clarifying the order of extensions being fixed.
* Explain CUs, EUs, SMs.
  This addresses #375.
* Add GPU example as desired by #366.
* Correct example.
* Escape all underscores in examples.
  They get interpreted otherwise by markdown.
* Use vendor-neutral terminology for GPU processing units
* Typo and minor wording

Signed-off-by: Kurt Garloff <[email protected]>
Signed-off-by: Matthias Büchse <[email protected]>
Co-authored-by: Matthias Büchse <[email protected]>

Standards/scs-0100-v3-flavor-naming.md

@@ -207,19 +207,19 @@ so users can expect some level of parallelism and independence.
 
 - SCS-2C-4-**10n**
 - SCS-2C-4-**10s**
-- SCS-2C-4-**10s**\_bms_z3
+- SCS-2C-4-**10s**\_bms\_z3
 - SCS-2C-4-**3x10s** <- Cloud creates three 10GB SSDs
-- SCS-2C-4-**3x10s**\_bms_z3
+- SCS-2C-4-**3x10s**\_bms\_z3
 - SCS-2C-4-**10** <- Cloud decides disk type
-- SCS-2C-4-**10**\_bms_z3
-- SCS-2C-4-**n** <- Cloud decides disk size (min_disk from image or larger)
-- SCS-2C-4-**n**\_bms_3
+- SCS-2C-4-**10**\_bms\_z3
+- SCS-2C-4-**n** <- Cloud decides disk size (min\_disk from image or larger)
+- SCS-2C-4-**n**\_bms\_3
 - SCS-2C-4- <- Cloud decides disk type and size
-- SCS-2C-4-\_bms_z3
-- SCS-2C-4-\_bms_z3h_GNa-64_ib
+- SCS-2C-4-\_bms\_z3
+- SCS-2C-4-\_bms\_z3h\_GNa-64\_ib
 - SCS-2C-4-\_ib
 - SCS-2C-4 <- You need to specify a boot volume yourself (boot from volume, or use `block_device_mapping_v2`)
-- SCS-2C-4_bms_z3
+- SCS-2C-4\_bms\_z3
 - SCS-2C-4-3x10 <- Cloud decides type and creates three 10GB volumes
 - ~~SCS-2C-4-**1.5n**~~ <- You must not specify disk sizes which are not in full GiBs
 
@@ -303,6 +303,9 @@ The extensions have the format:
 
 \[`_`hyp\]\[`_hwv`\]\[`_`arch\[N\]\[`h`\]\]\[`_`\[`G/g`\]X\[N\]\[`-`M\]\[`h`\]\]\[`_ib`\]
 
+Extensions are individually optional, but the ones that are used must appear in the order
+given in the above line.
+
 Remember that letters are case-sensitive.
 In case you wonder: Feature indicators are capitalized, modifiers are lower case.
 (An exception is the uppercase `_G` for a pass-through GPU vs. lowercase `_g` for vGPU.)
@@ -368,7 +371,7 @@ The options for arch are as follows:
 | ------- | -------------------- | --------------------------------- |
 | (none)  | Generic x86-64       | `x86_64`                          |
 | `i`     | Intel x86-64         | `x86_64`                          |
-| `z`     | AMD/Zen x86-64       | `x86_64`                          |
+| `z`     | AMD (Zen) x86-64     | `x86_64`                          |
 | `a`     | ARM v8+              | `aarch64`                         |
 | `r`     | RISC-V               | (not yet listed in Glance)        |
 
@@ -413,11 +416,11 @@ capabilities.
 - SCS-2C-4-10n\_**z3**
 - SCS-2C-4-10n\_**z3h**
 - SCS-2C-4-10n\_**z3hh**
-- SCS-2C-4-10n_bms_**z**
-- SCS-2C-4-10n_bms_**z3**
-- SCS-2C-4-10n_bms_**z3**
-- SCS-2C-4-10n_bms_**z3h**
-- SCS-2C-4-10n_bms_**z3hh** <- Bare Metal, AMD Milan with > 3.25GHz all core freq
+- SCS-2C-4-10n\_bms\_**z**
+- SCS-2C-4-10n\_bms\_**z3**
+- SCS-2C-4-10n\_bms\_**z3**
+- SCS-2C-4-10n\_bms\_**z3h**
+- SCS-2C-4-10n\_bms\_**z3hh** <- Bare Metal, AMD Milan with > 3.25GHz all core freq
 
 ### [OPTIONAL] GPU support
 
@@ -428,16 +431,16 @@ This extension provides more details on the specific GPU:
 - pass-through (`G`) vs. virtual GPU (`g`)
 - vendor (X)
 - generation (N)
-- no. of compute units / SMs / EUs (M) that are exposed (for pass-through) or assigned
+- number (M) of processing units that are exposed (for pass-through) or assigned; see table below for vendor-specific terminology
 - high-performance indicator (`h`)
 
-Note that the vendor letter X is mandatory, generation and compute units are optional.
+Note that the vendor letter X is mandatory, generation and processing units are optional.
 
-| GPU | Vendor |
-| --- | ------ |
-| N   | nVidia |
-| A   | AMD    |
-| I   | Intel  |
+| letter X | vendor | processing units                |
+| -------- | ------ | ------------------------------- |
+| `N`      | nVidia | streaming multiprocessors (SMs) |
+| `A`      | AMD    | compute units (CUs)             |
+| `I`      | Intel  | execution units (EUs)           |
 
 For nVidia, the generation N can be f=Fermi, k=Kepler, m=Maxwell, p=Pascal, v=Volta, t=turing, a=Ampere, l=Ada Lovelace, ...,
 for AMD GCN-x=0.x, RDNA1=1, RDNA2=2, RDNA3=3,
@@ -448,6 +451,10 @@ The optional `h` suffix to the compute unit count indicates high-performance (e.
 high bandwidth gfx memory such as HBM);
 `h` can be duplicated for even higher performance.
 
+Example: `SCS-16V-64-500s_GNa-14h`
+This flavor has a pass-through GPU nVidia Ampere with 14 SMs and either high-bandwidth memory or specially high frequencies.
+Looking through GPU specs you could guess it's 1/4 of an A30.
+
 ### [OPTIONAL] Infiniband
 
 Format: `_ib`