Add more context to router idea

riscv-router.md

@@ -28,31 +28,103 @@ And some broader tensions that have impacts here:
 - Modularity and reliability
 - Instrumentation and performance
 
+## Benefits
 
-### Comparison
+Networking hardware is a core primitive of making useful share-able services. Learning more about these pieces and how they fit together is attractive for our goals. It's also a natural starting point/lynchpin for "home lab" enthusiasts, since it's the intemediation between all the other devices. That's a low volume market, but one with higher quality feedback as people self-select into their interest.
+
+As a target, building a router equips us to practice skills like RTL modeling & FPGA development that seem broadly applicable. There's many potential side-avenues to explore & find an adjacent niche (e.g. FPGA development accelerator boards), with plenty of seemingly low-hanging fruit. It's also got a clear success criteria & natural way for us to self-validate: it solves a problem we actually have.
+
+Starting at the network edge keeps performance requirements relatively low: while it's not unreasonable for people to want 10gig, 25gig or even 100gig performance "inside" their network, almost no small networks have an internet connection faster than gigabit.
+
+## Risks
 
-with https://store.ui.com/us/en/pro/category/wired-edge-max-routing/products/er-x 
+The small-scale router space is somewhat crowded; most of the entrants are highly locked down, which we know doesn't provide either reliability or security at the limit. But the difference in quality between a device that experiences a (very loosely defined) "fault" every 10,000 hours vs every 1 million hours is _very_ hard to percieve at the point of sale. Instead, feature & price sensitivity probably dominate (in what rough proportion with reputation? extensibility?). In other words, it's possible I (Seth) am the only person in the world who cares about having a router that is as open as possible, modular & upgradable, and still affordable/low power.
 
+There's also a _long_ list of "things people expect a network to do," with very little in the way of coherent overlap (i.e. there's a very strange topology of "what is possible" vs. "what is easy"; many roads lead _near_ the same places, but not to them). It's also historically a domain occupied by a small number of experts, and held at "arm's length" as much as possible. This defensivenes is understandable given the abysmally poor quality of feedback when experimenting with the system, but it's also a collective property that may be hard to overcome in a product (i.e. every device on the network shares the same unhelpful "internet test" button that usually provides almost no value).
+
+### Comparison
+
+<table>
+ <th>
+   <td>Design Goal</td>
+   <td><a href="https://www.microchip.com/en-us/products/fpgas-and-plds/fpgas/igloo-2-fpgas">Igloo2 FPGA</a> + Marvell <del><a href="https://www.microchip.com/en-us/development-tool/m2gl-eval-kit">88E1340S</a></del> <a href="https://www.mouser.com/ProductDetail/Marvell/88E1543-A1-LKJ2C000?qs=vdi0iO8H4N1tQJodORiAVg%3D%3D">88E1543</a> PHY chip</td>
+   <td><a href="https://store.ui.com/us/en/pro/category/wired-edge-max-routing/products/er-x">EdgeRouter X</a></td>
+   <td><a href="https://store.ui.com/us/en/pro/category/all-wired/products/er-x-sfp">EdgeRouter X-SFP</a></td>
+   <td><a href="https://mikrotik.com/product/hex_s">Hex S</a></td>
+</th>
+ <tr><td>Price</td><td>$40</td><td>BOM Cost: $31<br>[~$14 (FPGA) + ~$17 (PHY)]</td><td>$60</td><td>$100</td><td>$80</td></tr>
+ <tr><td>Power (max)</td><td>5W</td><td>~1 W<br>[500mW (FPGA) + 280 mW (PHY)]</td><td colspan=2>5W (no SFP)</td><td>6 W (24 W with SFP attachment)</td></tr>
+ <tr><td>Power (avg)</td><td>??</td><td>??</td><td colspan=2>5W ?</td><td>??</td></tr>
+ <tr><td>ISA</td><td>RISC-V</td><td>None (RISC-V <a href="https://www.microchip.com/en-us/development-tool/futurem2gl-evb">available?</a>)</td><td colspan=3>MIPS</td></tr>
+ <tr><td>Networking</td><td>(2-4) 10/100/1000 RJ45 ports</td><td>up to (4) 10/100/1000 RJ45 Ports<br>(not priced)</td><td>(3) 10/100/1000 RJ45 ports<br>(1) 10/100/1000 RJ45 port (Data/PoE input)<br>(1) 10/100/1000 RJ45 port (Data/PoE passthrough)</td><td colspan=2>(5) 10/100/1000 RJ45 ports<br>(1) SFP port</td></tr>
+ <tr><td>PoE Output</td><td colspan=2>??</td><td>N/A</td><td>Passive 12W (24V)</td><td>Passive 28.5W (up to 57V)</td></tr>
+ <tr><td>Software</td><td>??</td><td><a href="https://www.microchip.com/en-us/products/fpgas-and-plds/ip-core-tools/coretse">CoreTSE "soft IP"</a> ($4,000 per "seat")<br>or, ??</td><td colspan=2>Linux (Vyatta)</td><td>Linux, lol ("RouterOS", which is <em>"allegedly"</em> violating the GPL)</td></tr>
+ <tr><td>Other Hardware</td>
+    <td>??</td>
+    <td>??</td>
+    <td colspan=2>
+     <table>
+      <tr><td>Processor</td><td>Dual-core 880 MHz, MIPS1004Kc</td></tr>
+      <tr><td>Memory</td><td>256 MB DDR3 RAM</td></tr>
+      <tr><td>Storage</td><td>256 MB NAND</td></tr>
+     </table>
+    </td>
+    <td>
+     <table>
+      <tr><td>Processor</td><td>Dual-core 880 MHz, MT7621A</td></tr>
+      <tr><td>Memory</td><td>256 MB DDR3 RAM</td></tr>
+      <tr><td>Storage</td><td>16 MB Flash</td></tr>
+      <tr><td>Expansion</td><td>microSD + USB</td></tr>
+     </table>
+    </td>
+
+ <tr><td>Ambient operating temperature</td><td>At least +10 to 40°C</td><td>??</td><td colspan=2>-10 to 45° C (14 to 113° F)</td><td>-40°C to 70°C</td></tr>
+ <tr><td>Ambient operating humidity</td><td>??</td><td>??</td><td colspan=2>10 to 90% noncondensing</td><td>??</td></tr>
+ <tr><td>Certifications</td><td>??</td><td>??</td><td colspan=2>CE, FCC, IC</td><td>CE, EAC, ROHS</td></tr>
+
+ <tr><td>Notes</td>
+  <td/>
+  <td>The 500mW estimate for the FPGA is <em>extremely</em> conservative; more typical numbers would seem to be an order of magnitude less. More work required to get better resolution.<br><br>Volume discounts for the chips start around 60-70 units and bring down the BOM cost by about $2.50<br><br>Gigabit Loopback Demo: https://www.microchip.com/en-us/application-notes/dg0633</td>
+  <td colspan=3/>
+ </tr>
+
+ <!--
+ <tr><td>TITLE</td><td>GOAL</td><td colspan=2>UBNT</td></tr>
+ -->
+
+
+</table>
 
 ### Gigabit Ethernet
 
 What is the minimum power (in watts) for a gigabit-capable device to route a signal?
+-> https://en.wikipedia.org/wiki/Category_5_cable#Characteristics lists the characteristic impedance (at 100 MHz) as 100Ω 
+-> https://en.wikipedia.org/wiki/Ethernet_physical_layer lists the voltage levels as ±2.5V
+
+So ignoring transmission line effects and switching frequencies—both of which seem significant here, since most cables are relatively long and the switching seems relatively far from a pure sine wave—and using `P_avg = (V_rms)^2 / R` we get ~ 31 mW per line, or 248 mW per 4-pair (8-line) link. So for a 4-port switch, we'd expect almost exactly 1W for the physical layer (is this an over- or under-estimate?).
 
 What is the minimum clockspeed? Per https://en.wikipedia.org/wiki/Gigabit_Ethernet#Copper it's a lot less than I thought: 62.5 MHz (1000 Gb / 4 lanes / 2 bits/clk / 2 ??? )
 
 
 ## Questions
+
 * Do we want to make a router or switch?
 * What is Router?
 * What is Switch?
-* What do *we* want it to do?
-* Who do we think this is for? Why do they want it? 
+* What do we want it to do?
 * Name?
   * Open Switch (lol, like a electronic switch?)
   * Closed Switch (lol, irony here since we're open?)
   * Mycelium (the small fungi filaments that connect nutrient pathways between trees and fungi)
   * \<moar ideas pls?\>
 
+## References
+
+- https://zipcpu.com/blog/2023/11/25/eth10g.html
+- https://www.chili-chips.xyz/open-cologne/ (note the paring of a Raspberry Pi CM4 "IO board" with a Lattice/Cologne FPGA)
+- https://baturin.org/docs/iproute2/
+- https://router7.org/
+- and the venerable https://en.wikipedia.org/wiki/List_of_network_protocols_(OSI_model)
 
 # software
 
@@ -94,6 +166,45 @@ How do we measure things at 1 gigabit?
 
 # part selection / pricing
 
+Common designs seem to include (up to) two "main" parts:
+
+* Gigabit-capable Ethernet PHY IC Transceiver
+* Controller SoC 
+
+With required auxiliary/supporting bits (not counting external resistors/capacitors):
+
+* Power (tbd)
+* Connectors (RJ-45)
+* "Magnetics" (transformer required by the PHY IC; possibly integrated into the connector)
+
+And lots of optional components:
+
+* Cooling (although, for <1W , even a heatsink is probably unnecessary)
+* Case
+* DC power source(s)
+* LEDs/indicators
+
+
+## Transceivers
+
+[Marvell "Alaska" 88E1543] [^whence-marvell-88E1543]: 4-port, moderate power (≤280mW), but expensive ($17; volume discounts up to ~10% [$15.50]). QFP package, which is familiar.
+
+[MaxLinear GPY111] [^whence-mouser-ethernet-ics]: 4-port, higher power (maybe? ≤460mW), cost effective ($3.50; volume discounts up to ~50% [$1.62]). VQFN package. Excellent datasheet.
+
+[MaxLinear GSW141] [^whence-mouser-ethernet-ics]: Fully featured "switch" IC, 4-port (+ 3 special ports), absolute power hog (≤924mW), cost effective ($5.62; volume discounts up to ~50% [$2.83]). MRQFN package (impossible to hand-solder).
+
+[Marvell "Alaska" 88E1543]: https://www.mouser.com/ProductDetail/Marvell/88E1543-A1-LKJ2C000?qs=vdi0iO8H4N1tQJodORiAVg%3D%3D
+[MaxLinear GPY111]: https://www.mouser.com/ProductDetail/MaxLinear/GPY111?qs=DRkmTr78QAS61OMQ%2FuuMhw%3D%3D
+[MaxLinear GSW141]: https://www.mouser.com/ProductDetail/MaxLinear/GSW141A3MC?qs=XAiT9M5g4x%2F91%2F1YTEsSCA%3D%3D
+
+[^whence-marvell-88E1543]: via the [Igloo 2 eval kit user guide](https://www.microchip.com/en-us/development-tool/m2gl-eval-kit#Documentation)§2.5 "Board Key Components", that board ships with the Marvell 88E1340S (which was hard to find), so I went looking for "closest available" and shortly thereafter ended up with the 88E1543.
+[^whence-mouser-ethernet-ics]: via [Mouser search][mouser-ethernet-ics-with-filters] in [Ethernet ICs category](https://www.mouser.com/c/semiconductors/communication-networking-ics/ethernet-ics/)
+
+[mouser-ethernet-ics-with-filters]: https://www.mouser.com/c/semiconductors/communication-networking-ics/ethernet-ics/?data%20rate=10%20Mb%2Fs%2C%20100%20Mb%2Fs%2C%201%20Gb%2Fs~~10%20Mb%2Fs%2C%20100%20Mb%2Fs%2C%201%20Gb%2Fs%2C%2010%20Gb%2Fs%7C~10%20Mb%2Fs%2C%20100%20Mb%2Fs%2C%201%20Gb%2Fs%2C%202.5%20Gb%2Fs~~10%20Mb%2Fs%2C%20100%20Mb%2Fs%2C%201%20Gb%2Fs%2C%202.5%20Gb%2Fs%2C%205%20Gb%2Fs%7C~100%20Mb%2Fs%2C%201%20Gb%2Fs%2C%2010%20Gb%2Fs~~100%20Mb%2Fs%2C%201%20Gb%2Fs%2C%202.5%20Gb%2Fs%2C%205%20Gb%2Fs%2C%2010%20Gb%2Fs%7C~1%20Gb%2Fs~~1%20Gb%2Fs%20to%201.3%20Gb%2Fs%7C~1%20Gb%2Fs%2C%2010%20Gb%2Fs~~1%20Gb%2Fs%2C%2010%20Gb%2Fs%2C%2040%20Gb%2Fs%7C~1%20Gb%2Fs%2C%202.5%20Gb%2Fs%2C%2010%20Gb%2Fs%7C~1%20Gb%2Fs%2C%202.5%20Gb%2Fs%2C%205%20Gb%2Fs%2C%2010%20Gb%2Fs~~1%20Gb%2Fs%2C%205%20Gb%2Fs%2C%2010%20Gb%2Fs%7C~1.25%20Gb%2Fs&number%20of%20transceivers=2%20Transceiver~~16%20Transceiver&rp=semiconductors%2Fcommunication-networking-ics%2Fethernet-ics%7C~Number%20of%20Transceivers%7C~Data%20Rate&sort=pricing
+
+
+## Controller SoC fpgas
+
 https://www.xilinx.com/products/boards-and-kits/arty.html ?
 
 Xilinx Spartan 7? (in the logic analyzer) 
@@ -106,6 +217,27 @@ This looks promising: https://www.microchip.com/en-us/products/fpgas-and-plds/fp
 
 And they start at ~$14/chip: https://www.mouser.com/c/?marcom=134980455&sort=pricing
 
+### Rough notes
+
+It seems like there's a few layers to try teasing apart here:
+
+- Development board/kit; probably we should expect to go through a few of these, probably starting with whatever's easiest for beginners and going from there? There's a lot of details in the FPGA design space, and it's not clear how to tease them apart yet. There's also a lot of play in the FPGA-board-maker space, too: most seem to also integrate whole SDKs on top of the board on top of the FPGA itself (see "programming software" bullet below)
+- "Production" chip: defining the envelope we need from the part is one thing; finding anyone brave enough to have an open FPGA core is a whole 'nother. Also, availability & price seem weirdly un-correlated to the dev boards that I've seen so far.
+- "Acceleration" chips: The best way to do FPGA development seems to be on an FPGA.... but, not "directly," instead using the FPGA to coorindate with the RTL simulator. What's _that_ chip selection look like?
+  - Amazon will rent you an [F1 instance with a single (1) attached FPGA](https://instances.vantage.sh/aws/ec2/f1.2xlarge) for $1.6500/hr on-demand (~$0.6488/hr spot), which is about $1200 a month ($500 for spot). They've got a density problem, it seems, since the largest size is an [`f1.16xlarge`](https://instances.vantage.sh/aws/ec2/f1.16xlarge) which comes with 8 FPGAs and a whopping 976.0 GiB of RAM with	64 vCPUs; that and the dedicated 25 Gigabit networking suggest they're renting you the whole blade at that point. But: in our (very limited) experience with RTL simulation, a fairly complex model with no acceleration takes on the order of ones of CPUs and tens of _Megabytes_ of memory. Meaning, a burst-credit model for way oversubscribing the CPU and nano- or micro-scale memory (0.5 to 1 GB) might get us equivalent performance to the `f1.2xlarge` at literally 1/100th the cost of the `f1.2xlarge`. But, to sell us that, assuming their blade is already otherwise "minimally sized" for an AWS DC, they'd need to slot some 512 or 1024 FPGAs per blade. Maybe in the `f2` class, eh?
+  - Or, it's possible that _is_ a good deal for running a workload more than a couple hours a month, and I've wildly missed my guesses above. In which case, the FPGA itself makes up a significant proportion of the price, and the kind of hardware that people use to simulate other hardware costs on the order of tens of thousands of dollars. I sure hope not!
+  - But, uh, "firesim" (which is the FPGA accelerator underneath chipyard?) [supports](https://docs.fires.im/en/stable/FireSim-Basics.html#choose-your-platform-to-get-started) the Xilinx Alveo U250 (or U280, which is [discontinued](https://www.xilinx.com/products/boards-and-kits/alveo/u280.html)), [Xilinx VCU118](url), and the RHS Research Nitefury II. That's a [$10,000 "accelerator card"](https://www.mouser.com/ProductDetail/AMD-Xilinx/A-U250-A64G-PQ-G?qs=unwgFEO1A6vi%2FTDpEsBygA%3D%3D), a [$10,000 evaluation kit](https://www.xilinx.com/products/boards-and-kits/vcu118.html) (although you can back-order the chip itself inside the evaluation board for a [cool $50,000](https://www.digikey.com/en/products/detail/amd/XCVU9P-L2FLGA2104E/7421960), which, uh 😵‍💫). But, [RHS Research](https://rhsresearch.com/pages/about-us) to the rescue! Their Nitefury II is a M.2 form-factor accelerator for $150, which is an awful lot more "in budget", even if it only seems to be available via [Amazon](https://www.amazon.com/dp/B0B9FMBF6C). Also of interest: https://www.crowdsupply.com/rhs-research & https://github.com/RHSResearchLLC/NiteFury-and-LiteFury . 
+- programming software: seems like an awful lot of _that_ stack is vendor-specific, locked-down, slow, lacking in Linux support (but there's always WINE), and/or varies greatly in quality. 
+- so-called "IP" availability: there's a somewhat eclectic mix of "parts" available to "plug in" to a design.
+  - it sure would be nice to have an index where we could say, e.g. "ETH PHY 1000" and get a list of gigabit-capable "core"s (not the CPU kind of "core"). Maybe someone should make that (us?).
+  - To be useful, it'd probably also need to be further filterable by "integration details," maybe HDL? "inward" facing protocols (SPI; TileLink; that ARM interlink protocol thing; etc.)?
+
+## Connectors
+
+https://www.mouser.com/c/connectors/modular-connectors-ethernet-connectors/
+
+With integrated magnetics + LEDs, might be ~[$8/port](https://www.mouser.com/ProductDetail/Taoglas/TMJY001DYDZ5NL?qs=1Kr7Jg1SGW8e3hAY3JZFvA%3D%3D)? More research needed.
+
 # compliance
 
 ## being compliant