Strange chip: Teardown of a vintage IBM token ring controller
righto.com
righto.com
Later they had these MAU devices that let you build star like topologies where the mau would bypass inactive ports.
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.
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.
I'm sure Token Ring would have solved it the same way.
I think the point about IBM's licensing is valid.
Perhaps, but "the problem" was shared access to a single piece of wire. Switches solved the problem by ending sharing - each piece of wire had exactly one computer.
So sure, a switch would have fixed Token Ring's lost token problem - by eliminating the token. I'm not sure it could be called "Token Ring" at that point as there is no token, and no ring.
He didn't seem to be lying... he did something using mouse/keyboard on his machine and my machine couldn't use the network, and then after a couple kids complained about the network being down, he discretely did something on his machine and things were fixed.
I was always confused as to how he was fast enough or even that his computer having the token was user-visible without installing specialist tools on the school's computers. If he were to start a large file transfer, would that cause him to hold the AppleTalk token for a long time, and give him visibility via the progress bar?
I thought there was sub-second upper bound on how long the token would be held, even if your machine still had data to send. Am I mistaken about AppleTalk token ring networking?
That does remind me of a story I heard, that the zero page was mapped, and the first 64 bits of the zero page were initialized to zero at startup. So, if you derefernced or duble-dereferenced NULL as an *int, *float, *double, **int, **float, **double, etc., there would be no error and you'd get 0 or 0.0. Apparently, the Excel port for Macs had quite a few NULL double-dereferences, either intentionally taking advantage of this "feature" or by accident. Many developers installed a system extension that would set the first 32 bits of memory to a value larger than the amount of installed memory, guaranteeing an error if NULL were double-dereferenced.*
For the article itself, probably it is tangential and thus you were correct to excise it. I was commenting on a claim about IBM (hardly the only token passing network) which was itself tangential to the arrival topic.
I'd never heard of this before. TIL.
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.
IBM Networking Systems spent much of the early 1990s dithering and thrashing about how to compete with Novell and Microsoft's networking and almost completely missed the rise of TCP/IP both in the enterprise as well as the public Internet. When I first started doing networking development for OS/2 at IBM I had to get special permission to get the $1000+ TCP/IP networking kit because it was "owned" by NSD which really, desperately, wanted everyone to develop applications for APPC. APPC was tightly tied to Token Ring and thus they really also minimized R&D into TCP/IP over TR networks.
Although IBM "woke up" to the Internet and personal computer networking with the Lotus deal, it took NSD another year or more to really shift gears, and by then IBM had had enough and dumped the assets onto Cisco for a song.
If kens is still around, an odd source for token ring information might be Carnegie Mellon, which implemented a MASSIVE TR network circa 1986 or 1987 with Type 1 connectors in every dorm room on campus so students could access Andrew from …anywhere.
Unlikely. People forget that a star topology (Token Ring with MAU--the MAU was ferociously expensive) was expensive in that day and age--both in terms of technology (lots more VLSI) and infrastructure (everything was mostly wired up with RJ-11/shitty wiring for voice and nobody had RJ45/Cat5).
Ethernet installations evolved from coax to hubs to switches as the price came down.
Yes, eventually star topology won, but it got there in steps--and Token Ring couldn't do that.
People didn't have RJ-45 and Cat5 back in 1988-1990. The existing ports in every office building were RJ11 voice (Cat3 garbage) and maybe coax for some reason.
So, normally, networking started as "wire the computers in that room". That was generally coax at the beginning. And you would keep adding computers.
Eventually, somebody got tired of always debugging where the networking break in the coax was and managed to finagle a single hub in that room. But only one hub because they were kinda expensive.
At some point you had overflow and then it went "Connect the main room to another room or two" which meant an actual cable pull somehow (probably a midnight session through the drop ceiling) and probably went into a hub in the main room--but only one hub per room max because they were kinda expensive.
And, finally, you got enough computers that congestion was now an issue and you got to use an actual switch (which was really expensive--so generally you only used that to connect to the hubs and isolate them) and could now get people to officially pull cable.
This played out from about 1988 (coax dominates) to about 1998 (TCP/IP has finally won and ethernet switches dominate and hubs disappear), I would say. For most of that range, a system based on Ethernet hardware would have been dramatically cheaper than one based on Token Ring hardware until Ethernet switches became ubiquitous (by which time Token Ring was dead)--even if the interface cards were the same price.
And, remember, some of the Ethernet cards were GARBAGE, yet people beat them into submission because "real" ones like the DEC Tulip cards were so expensive. One of the reasons for the ascendancy of Linux was its support for so much complete garbage in terms of hardware.
And, to add insult to injury, 10Base Ethernet would generally work on Cat3 garbage that Token Ring simply would have no hope on. And that meant a dramatic decrease in your physical plant support cost.
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)
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.
Occasionally I find interesting chip art such as a tiger on a Dallas Semiconductor chip: https://en.wikipedia.org/wiki/Chip_art
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
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.
>"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?
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.
Interesting. Can you elaborate on why using "base" is a stretch here? I don't think I've heard this before. It's been a while since I've looked at layer 1 but isn't Ethernet just Manchester encoding? What other signal tricks are generally used?
Might you or anyone else have any good resources for Ethernet PHY circuits?
High speed on copper, for networking anyway, has gone all analog now. That's more of a 'broad'-band (in the literal sense) than 'base'-band (in the single frequency, off/on) sense.
Edit:
The Wikipedia page for broadband says it better: "The key difference is that what is typically considered a broadband signal in this sense is a signal that occupies multiple (non-masking, orthogonal) passbands, thus allowing for much higher throughput over a single medium but with additional complexity in the transmitter/receiver circuitry." -- https://en.wikipedia.org/wiki/Broadband
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.
If they were test pads something more like the solder ball or a normal pad might be expected.
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 ...
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.
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/ 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_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 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).
A more popular token bus was the 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_netwo...
https://en.wikipedia.org/wiki/Fiber_Distributed_Data_Interfa...
https://sci-hub.se/10.1109/4.45001 https://sci-hub.se/10.1147/rd.342.0416 https://sci-hub.se/10.1147/rd.342.0428