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Strange chip: Teardown of a vintage IBM token ring controller
- kens 6y agoAuthor here if anyone wants to discuss IBM's chips.
- 7800 6y agoWhat 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 6y agoI'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 https://en.wikipedia.org/wiki/Chip_art
- kayson 6y agoChip 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 https://imgur.com/a/AkB10A0
- parsecs 6y agoWhat was the function of that piece of silicon?
- kayson 6y agoThe 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 6y agoThis 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 6y agoI 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 6y ago> 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.
- h2odragon 6y agoCould 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 6y agoThe mystery loops might be some sort of impedance matching. 16 megahertz seems low for that sort of magic, but I don't know.
- mjevans 6y agoMy _guess_ was some sort of (attempt at?) very minor inductance / capacitive correction factor; leaning a bit more towards capacitive for the lack of more loops. In college I tried to do something similar in a term project by using all of the spare surface space on the PCB as a capacitive fill attached to the power supply. If they were test pads something more like the solder ball or a normal pad might be expected.
- ch_123 6y ago> 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 6y agoThis 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 ...
- PhantomGremlin 6y agoIn footnote #6 you ask which devices are PMOS and which are NMOS. My guess is that the PMOS are at the bottom, so you have a NOR gate. In typical CMOS processes the PMOS transistors have lower carrier mobility than NMOS transistors. Holes are slower than electrons. So in standard cells the PMOS transistors are made physically larger to compensate. This helps the device output H->L and L->H transitions be more symmetric.
- pontifk8r 6y agoWhen 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 6y agoI've asked around a bit, but haven't found anyone with information on the UC architecture.
- reaperducer 6y agoI wonder if it's buried somewhere in Usenet.
- bsder 6y agoIt's probably buried somewhere in the IBM Journal of Research and Development.
- devoutsalsa 6y agoI 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 6y agoThe 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 6y agoYeah, we had an MAU, but I’d forgotten the term.
- TedDoesntTalk 6y agoToken-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.
- jhoechtl 6y agoConnectors have been bulky and wires thick compared to ethernet.
- wmf 6y agoWhich was just IBM over-engineering. Token ring ran fine on cat5 with RJ45.
- TedDoesntTalk 6y agoThey did shrink the connectors later on and move away from coax. There’s no reason token-ring can’t work over RJ-45 with 4 twisted pairs.
- LargoLasskhyfv 6y agoAhem! https://en.wikipedia.org/wiki/ARCNET https://en.wikipedia.org/wiki/ARCNET
- ncmncm 6y agoLinux used to have ARCnet drivers.
- LargoLasskhyfv 6y agoIt used to have drivers for https://en.wikipedia.org/wiki/Fiber_Distributed_Data_Interface https://en.wikipedia.org/wiki/Fiber_Distributed_Data_Interfa... too, which is another token passing network. Or at least I had drivers for Linux for them. Can't remember exactly anymore, worked for a while in government institions which used nothing else for networking. FDDI I mean, not Linux, that was an experimental exception. Which was funny, because hey, government, modern equipment? Nope... TERMINALS! Which were plugged into the ring via matchbox-like media-converters going from 100Mbit/s down to 19.200bit/s whith weird parity and stop bits. At least they didn't need a separate PSU(wall wart) because the full DB25 of the RS-232 powered them somehow.
- a-dub 6y agoi 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.
- jecel 6y agoWhat you described is known as a "Token Bus". The one developed by General Motors became an IEEE standard (802.4) for a while as an alternative to Ethernet (802.3) and the Token Ring (802.5) but was quickly forgotten. A more popular token bus was the Arcnet. https://en.wikipedia.org/wiki/ARCNET https://en.wikipedia.org/wiki/ARCNET While IBM's Token Ring was the most famous one there were others: https://en.wikipedia.org/wiki/Cambridge_Ring_(computer_network) https://en.wikipedia.org/wiki/Cambridge_Ring_(computer_netwo... https://en.wikipedia.org/wiki/Fiber_Distributed_Data_Interface https://en.wikipedia.org/wiki/Fiber_Distributed_Data_Interfa... https://en.wikipedia.org/wiki/Scalable_Coherent_Interface https://en.wikipedia.org/wiki/Scalable_Coherent_Interface
- 2sk21 6y agoI 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.
- jcims 6y agoI had to go on a fishing expedition to find a token ring card that had Linux drivers (IIRC it was an ISA bus) for my shiny new pentium pro machine back in the mid 90’s. Those were the days, ‘hey boss, can i build a machine? sure, get a quote for the parts and send it over.’ Nobody gave a shot that it want a standard build it that nodding but me had root, etc etc.
- Zenst 6y agoI was sorting out some old box's just the other day and in one I found an old IBM PCMCIA Token Ring adapter, in the box with manual and connecting cable. I put it aside, it's so old that I won't ever use but probably niche enough today that I felt worth keeping onto or selling over e-wasting it.
- fnord77 6y agodo companies ever release their engineering documents for vintage systems?
- kens 6y agoI don't know about official releases of documents, but there are a lot of vintage documents on bitsavers.org.
- tal8d 6y agoIBM has a very long history of diligent notetaking, maintaining several journals dedicated to internal development stretching back into the 50's. While I certainly haven't read everything, I've read enough to feel comfortable saying that the quality has had a sharp decline as transparent marketing replaced useful engineering. I suspect I'm not the only one who felt that way, because they recently shuttered those operations and tragically handed everything (from what I can tell) over to the paywalls. I generally don't feel much one way or the other about corporations, but seeing IBM decay like this genuinely makes me gloomy. https://sci-hub.se/10.1109/4.45001 https://sci-hub.se/10.1109/4.45001 https://sci-hub.se/10.1147/rd.342.0416 https://sci-hub.se/10.1147/rd.342.0416 https://sci-hub.se/10.1147/rd.342.0428 https://sci-hub.se/10.1147/rd.342.0428
- userbinator 6y agoI'd be curious to see a comparison with the die of something like the ubiquitious Realtek NICs. They're definitely a mixed-signal design given that everything is on one chip.
- rasz 6y agoRealtek RTL8019AS and RTL8029AS are a straight reimplementation (with few improvements in native mode like full duplex, sleep mode, PnP, auto polarity) of National Semiconductor DP8390 which in turn was the basis for Novell NetWare NE1000/NE2000 standard. https://en.wikipedia.org/wiki/NE1000 https://en.wikipedia.org/wiki/NE1000 If you really want to go back in time into hardcore beginning you need to look at something like 3Com EtherLink 3C501 aka IBM Ethernet 4 (IE-4) https://www.os2museum.com/wp/emulating-etherlink/ https://www.os2museum.com/wp/emulating-etherlink/ made somewhat famous in networking circles by Linux Kernel driver comment "Don’t purchase this card, even as a joke.". 3C501 itself was an ASIC shrink of earlier design 3C500, the first original IBM Ethernet, here in all of its huge glory: https://static.wixstatic.com/media/a03cac_005e3e9eb62b47c29265cb94a99f68aa~mv2_d_3264_2448_s_4_2.jpg/v1/fill/w_3264,h_2448,fp_0.50_0.50,q_90/a03cac_005e3e9eb62b47c29265cb94a99f68aa~mv2_d_3264_2448_s_4_2.jpg https://static.wixstatic.com/media/a03cac_005e3e9eb62b47c292... Its surprising to learn the cheap and considered crappy RTL8019AS was technically better than what most would call top of the shelf 3Com 3C509B thanks to twice the buffer size (16 vs 8 KB). YouTube Computer History Museum "Oral History of Kanwal Rekhi" (Excelan, Novell CTO) https://www.youtube.com/watch?v=ox0e7yVgsXM https://www.youtube.com/watch?v=ox0e7yVgsXM has some interesting stories about early Ethernet adapters made by Excelan, Novell, their strategies, Lite products and bonkers ideas (Mormon run, trying to compete with Microsoft, hate of Unix despite owning it).
- kens 6y agoThat vintage Ethernet card you linked to is quite something. I like the big metal-can tuned inductors like a 1970s TV set. It has a lot of blue bodge wires to fix things. M favorite is the chip with four X's of wire across it. Clearly they designed something backwards.
- jhallenworld 6y agoIBM's logic synthesis tool (equivalent to Design Compiler) was called "Bool-Dozer". It may have made this chip, but I don't know if the time periods overlapped.