> But pushing gigabit ethernet over that doesn't work reliably anymore or even at all. It's very much a universal problem with higher speeds. And the notion that "you can make any speed reliable and fool proof" is just absurd denying physics.
I'm not denying physics. Funny that you use Gigabit Ethernet as an example... I'm still debugging a hobby Gigabit Ethernet project. For some complicated reasons, It has to use a standard BASE1000-T PHY, but instead of communicating over a CAT-6 cable, it has to communicate over the circuit board backplane. Previous prototypes couldn't even reliably auto-negotiate. Apparently, in Ethernet, not only a long cable and heavy attenuation can be the problem, an extremely short link with low attenuation can also confuse the "Feed-Forward Equalization" DSP algorithm in the PHY and create problems. I totally understand the inherent challenges of high-speed designs and have some hand-on experience.
But I have to say, yes, you can make any speed reliable, given a controlled environment and a reasonable technical constraints. It's called engineering. Howard Johnson (the author of the famed engineering handbook High-Speed Digital Design - A Handbook of Black Magic), in a 1997 article on Gigabit Ethernet, which he heavily involved in its standardization, he discussed its enormous challenges [0]...
> Key ingredients in any Gigabit Ethernet design will include:
> Careful control of clock skew on the 125-MHz 10-bit bus.
> Attention to crosstalk between massive, 125 MHz TTL-level parallel buses and critical high-speed serial circuits.
> EMI considerations on the serial cables (if you are not an expert in this area, I suggest choose fiber)
> Huge pin counts, especially on complex switching or routing ASICS, some of which will be using 512-bit bus interconnections
> More than usual emphasis on time-to-market; everybody will want their products ASAP
> If you thought Fast Ethernet 100BASE-T layouts were tricky, think again. Gigabit Ethernet is going to be faster, with more parallel signals, and tighter layout constraints.
However, he also said,
> It will work, and it will work reliably, but you will have to follow the rules.
You can make any speed reliable within a reasonable engineering constrict, and in a controlled setup. Using off-the-shelf PHYs and controllers, doing hardware compliance testing, and installing good cables are all supposed to create this controlled setup. Failures to do so is what we call "hardware compliance problems". I agree that it's definitely not foolproof. Saying it is would be denying physics, but I didn't say that. EMI/EFI is a serious problem for USB 3.o. I'm only saying that a lot of USB 3.0 problems in practice is bad hardware compliance, true electrical problems can be fewer.
I'm not denying physics. Funny that you use Gigabit Ethernet as an example... I'm still debugging a hobby Gigabit Ethernet project. For some complicated reasons, It has to use a standard BASE1000-T PHY, but instead of communicating over a CAT-6 cable, it has to communicate over the circuit board backplane. Previous prototypes couldn't even reliably auto-negotiate. Apparently, in Ethernet, not only a long cable and heavy attenuation can be the problem, an extremely short link with low attenuation can also confuse the "Feed-Forward Equalization" DSP algorithm in the PHY and create problems. I totally understand the inherent challenges of high-speed designs and have some hand-on experience.
But I have to say, yes, you can make any speed reliable, given a controlled environment and a reasonable technical constraints. It's called engineering. Howard Johnson (the author of the famed engineering handbook High-Speed Digital Design - A Handbook of Black Magic), in a 1997 article on Gigabit Ethernet, which he heavily involved in its standardization, he discussed its enormous challenges [0]...
> Key ingredients in any Gigabit Ethernet design will include:
> Careful control of clock skew on the 125-MHz 10-bit bus.
> Attention to crosstalk between massive, 125 MHz TTL-level parallel buses and critical high-speed serial circuits.
> EMI considerations on the serial cables (if you are not an expert in this area, I suggest choose fiber)
> Huge pin counts, especially on complex switching or routing ASICS, some of which will be using 512-bit bus interconnections
> More than usual emphasis on time-to-market; everybody will want their products ASAP
> If you thought Fast Ethernet 100BASE-T layouts were tricky, think again. Gigabit Ethernet is going to be faster, with more parallel signals, and tighter layout constraints.
However, he also said,
> It will work, and it will work reliably, but you will have to follow the rules.
You can make any speed reliable within a reasonable engineering constrict, and in a controlled setup. Using off-the-shelf PHYs and controllers, doing hardware compliance testing, and installing good cables are all supposed to create this controlled setup. Failures to do so is what we call "hardware compliance problems". I agree that it's definitely not foolproof. Saying it is would be denying physics, but I didn't say that. EMI/EFI is a serious problem for USB 3.o. I'm only saying that a lot of USB 3.0 problems in practice is bad hardware compliance, true electrical problems can be fewer.
[0] http://www.sigcon.com/Pubs/straight/gigabit.htm