Author here if anyone wants to discuss IBM's chips.
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?
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.
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
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 ...