[HN Gopher] Strange chip: Teardown of a vintage IBM token ring c...
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Strange chip: Teardown of a vintage IBM token ring controller
Author : parsecs
Score : 86 points
Date : 2021-02-28 18:06 UTC (4 hours ago)
(HTM) web link (www.righto.com)
(TXT) w3m dump (www.righto.com)
| devoutsalsa wrote:
| I worked on a token ring network back in the 90s. There were more
| employees than network ports. So every time someone complained of
| not having network connectivity, we'd find a network cable where
| the light on the port wasn't lit up from activity, usually
| because someone was out sick or on vacation. If everyone decided
| to come into the office, we would have had a problem, but I don't
| think it ever happened while I was there.
| nullc wrote:
| The cards are supposted to bypass themselves when powered off,
| that's what those relays were for.
|
| Later they had these MAU devices that let you build star like
| topologies where the mau would bypass inactive ports.
| devoutsalsa wrote:
| Yeah, we had an MAU, but I'd forgotten the term.
| 2sk21 wrote:
| I encountered the wierd token ring connector for the first time
| when I joined IBM in the early 1990s. But the proprietary
| connector got replaced with a standard RJ45 jack later on. But by
| that time, it was clear that Ethernet had won.
| TedDoesntTalk wrote:
| Token-ring networks could have ruled the world. But IBM's
| insistence on licensing fees made the equipment expensive
| compared to Ethernet.
|
| Token-ring was faster: 16 Mbps with no collisions, vs Ethernet's
| 10 Mbps in a perfect world... but in reality it was slower when
| accounting for collisons and retries. No so with token ring.
|
| If IBM had licensed the tech without fees, hardware would have
| been competitive to Ethernet and today we'd all be using 1 Gbps
| token ring in our homes.
|
| But now I'd be surprised if a token-ring driver even exists for
| Windows 10 or MacOS.
| gumby wrote:
| The biggest problem with token passing systems is the cost of
| losing the token (machine holding it crashes) or failing to
| yield (when you then have a pope-antipope situation).
|
| Ethernet has an immediately worse system (everybody has to do
| the backoff, and on a crowded network that can be painful) but
| on an amortized bases not-as-bad system. Also adding more hosts
| is pretty much automatic. Consider it a positive example of the
| "worse is better" paradigm.
| rodgerd wrote:
| Licensing (alongside the MCA debacle) was definitely a driver,
| as was the more complex topology for even a simple token ring
| network compared to a simple ethernet network.
|
| Ultimately the brute-force improvement in efficiency given by
| developing ethernet switching settled the argument, IMO. Once
| you could practically utilize the bulk of the theoretical
| bandwidth of ethernet, token ring was toast. Switching was the
| Pentium Pro of network architectures.
| LargoLasskhyfv wrote:
| Ahem! https://en.wikipedia.org/wiki/ARCNET
| jhoechtl wrote:
| Connectors have been bulky and wires thick compared to
| ethernet.
| wmf wrote:
| Which was just IBM over-engineering. Token ring ran fine on
| cat5 with RJ45.
| pontifk8r wrote:
| When tearing down some of this technology, there's almost an
| undercurrent "how this works is a mystery today" -- but the
| humans that still worked on some of these micro-marvels are
| probably still alive. Have you had success in finding people that
| did work on these designs, for example in the case of the
| "universal controller (UC) architecture" which might merit an
| article all its own?
| kens wrote:
| I've asked around a bit, but haven't found anyone with
| information on the UC architecture.
| reaperducer wrote:
| I wonder if it's buried somewhere in Usenet.
| a-dub wrote:
| i didn't know the actual data got passed from host to host... i
| was always under the impression that the data was broadcast and
| merely the token or "talking stick" got passed from host to host
| in a ring.
| kens wrote:
| Author here if anyone wants to discuss IBM's chips.
| h2odragon wrote:
| Could the mystery analog loops be impedance matching / baluns?
| My first thought, the way they stand out bare on the chip,
| seems similar to other RF magic.
| kens wrote:
| The mystery loops might be some sort of impedance matching.
| 16 megahertz seems low for that sort of magic, but I don't
| know.
| ch_123 wrote:
| > IBM calls this "microcode", but it's unclear if this is
| microcode in the usual sense or just firmware instructions.
|
| IBM had all sorts of unconventional usages of the word
| "microcode", e.g. parts of the OS/400 operating system were
| referred to as the "Horizontal and vertical microcode" (they
| were in fact the kernel of the operating system)
| realo wrote:
| This flip chip was likely made at the IBM Bromont plant in
| Quebec.
|
| I visited it a long time ago.
|
| If you x-ray (?) or break the ceramic substrate (with the
| actual pins) you might find it to be a complex multi-layer
| piece ...
| 7800 wrote:
| What is the strangest thing you've ever seen in a chip? (e.g.
| has anything ever hinted at either a lucky accident that relied
| on physical laws that weren't understood or tech that seemed
| too advanced to have been developed by the team that developed
| it?)
|
| Also- the strange parts of the chip spell DDB, which may be
| relevant, as the V DDB is mentioned in one of the MAU design
| patents. Or DDB possibly could be the initials of the team or
| designers. It could have also served a practical purpose.
| kens wrote:
| I've seen a few things on chips that don't make sense, such
| as wires to nowhere. Then I figured out that these were bug
| fixes where they had cut connections.
|
| Occasionally I find interesting chip art such as a tiger on a
| Dallas Semiconductor chip:
| https://en.wikipedia.org/wiki/Chip_art
| kayson wrote:
| Chip art is a lot of fun! Years ago when I was working at a
| startup, we had a wooden statue in the office of a monkey
| holding a cell phone. Over time he was further accessorized
| with a hardhat and an official company badge. On one of our
| prototype tapeouts, we made a not-insignificant effort to
| render a proper photo of it onto the top layer metal.
|
| The tricky thing was getting multiple colors (shades,
| really) using what amounts to a single color. Back then, we
| didn't have any fancy filters like "sketch mode" to turn it
| into a line drawing, and we were limited to some extent by
| process design rules for metal size, spacing, density, etc.
|
| We ended up opening the image in GIMP, and converting it to
| grayscale, then true black and white (1-bit color) by
| upscaling and using some filter where it preserves the
| shades by setting the average density of black pixels in an
| area to match the shade of gray of the pixel in the
| original. Then we wrote a script that mapped black pixels
| to solid metal, and white pixels to empty space, on a grid
| in such a way that all Design Rules were met.
|
| It wasn't a perfect result but I think it turned out
| alright! https://imgur.com/a/AkB10A0
| parsecs wrote:
| What was the function of that piece of silicon?
| kayson wrote:
| The whole die was a cellular transceiver. If I remember
| correctly that particular spot happened to be empty on
| the top layer. Foundries require a minimum density of
| metal on every layer, so we would have had to put dummy
| pieces of metal there anyways. We figured why not put a
| picture
| bogomipz wrote:
| This was another great post. I hope to see you do an Ethernet
| chip/card post in the future. I had a couple question about the
| following:
|
| >"The block diagram below shows the complex functionality of
| the chip. Starting in the upper right, the analog front end
| circuitry communicates with the ring. The analog front end
| extracts the clock and data from the network signals."
|
| Do all non-optical network cards have a similar analog circuit
| as well? Is this generally the transceiver chip on the card?
|
| >"The chip's logic is implemented with a CMOS standard cell
| library and consists of about 24,000 gates. The idea of
| standard-cell logic is that each function (such as a NAND gate
| or latch) has a standard layout."
|
| Are these cell libraries the same as an IP block that you would
| license today when designing a chip? Did cell libraries become
| common around the time of this chip?
| kens wrote:
| I haven't looked at Ethernet chips in detail, but they have
| similar analog circuitry. A "PHY" (physical layer) module
| does the analog encoding and decoding.
|
| Standard cell libraries are lower-level than IP blocks since
| you're dealing with gates rather than functional units. I'm
| sure someone here knows about how they are licensed.
|
| On the chip I looked at, the analog module and the CPU were
| treated as IP blocks. These blocks were built by IBM so the
| intellectual property itself wasn't an issue. But the blocks
| were designed by other teams and essentially dropped onto the
| chip unchanged. For the revised version of the chip, they
| redesigned the logic but kept the original analog and CPU
| blocks.
| dfox wrote:
| > Do all non-optical network cards have a similar analog
| circuit as well? Is this generally the transceiver chip on
| the card?
|
| Even optical cards have this kind of circuitry in the PHY
| chip. While the SFP module usually contains surprising amount
| of logic, most of it has to do with configuration and testing
| and in the end it is just an pair of LEDs with configurable
| analog amplifiers.
|
| On the other hand for modern ethernet over TP (1Gbps and up)
| the analog interface circuitry is significantly more complex
| (and power hungry), because calling the thing baseband (the
| "base" in "1000-base-T") somewhat stretches the definition of
| the word. It uses various line coding and signal processing
| tricks to squeeze all the bandwith out of the wire.
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(page generated 2021-02-28 23:00 UTC)