Author here for your IBM 1401 questions :-)
It reminds me of how NASA simply lost so much of the original media, and what he have today is either purely accidental or the result of a considerable amount of work done by volunteer restoration groups. We really need to get a grip on this problem now, and it would be nice if IBM would actually help out with that - instead of leaving it to volunteers.
So in things like amplifiers it gives you less zero point crossover distortion. In digital I believe it lends to a faster switch time but I could be very wrong on this part.
Germanium is much more rare so the cost is naturally higher...from what I know.
I can't imagine a logic circuit of that era that was technically capable of being clocked at 100Mhz, 30 years before these frequencies became the norm.
Based on the speed, it's plausible that it is a type of ECL, but I don't know where the diodes would fit in. IBM had other names such as current-steering logic for ECL.
Keep in mind that the 10ns speed doesn't mean you can run at 100 Mhz, since there are likely to be multiple levels of logic, as well as other delays. But it's still pretty fast.
I understand that transistors amplify current but how do they amplify voltage (like in CMOS)? Isn't voltage going to amplify current also?
I never understood this.
In a bipolar (NPN or PNP) transistor, the current through the base causes a larger current through the collector, amplifying by the beta factor. So the transistor is amplifying current. But the current depends on the voltage between the base and emitter, so from that perspective the voltage controls the transistor too.
Whether you're amplifying current or voltage depends on the circuit, so I can't give more than a handwaving answer.
In field effect transistor (in which the actual physics involved are at least for me simpler to grasp) the gate is isolated from everything else and voltage at the base directly changes the geometry of the conductive channel between the S and D pins. In effect the gate voltage directly influences the resistance of the component. MOS is an name for particular practical realization of this mental model.
In bipolar junction transistor (ie. PNP/NPN) there are two diodes that are positioned just so that conduction of one of them influences the other in such a way that when one is positively biased the other will conduct even when reverse biased. For the typical BJT these two diodes have significantly different construction and thus there is difference between emittor and collector, but the effect works both ways (and in fact many circuits will somewhat work even with the 2N3904 connected the wrong way around). The effect is also caused by change of properties of doped semiconductor material in response to electric field gradient but (at least for me) there is no directly applicable model involving discrete lumped components changing their parameters in response to external stimuli that matches the underlying physical principle.
Your DC battery or power supply provides your headroom, and the transistor Base or Gate senses a small increment of that voltage and can sometimes deliver as much current as it takes to push the voltage across a resistance or impedance right up to the rails.
Any voltage through a resistor will produce a current, and any current through a resistor will produce a voltage. By properly connecting resistors at the transistor base and collector, one can turn a driving voltage into a current and the collector current back into an output voltage. The basic common emitter transistor amplifier circuit is a good example as it shows how a current amplifier like a transistor is used to amplify a voltage. Resistors are the secret that allow all permutations: voltage to voltage, current to voltage, voltage to current, current to current.
In BJT transistors the "control stimulus" is the current flowing through the base pin, while for (MOS)FET transistors it's a voltage potential between the gate and source pins.
The amplification happens because in the right region the change in effective resistance is high for small variations in the "control stimulus".
If you drive a BJT with a resistor in front of the base pin, you can drive it with a voltage. If you put a resistor between the gate and source pins, you can drive a MOSFET with a current source.
So the way you control them is different, but what they end up doing is the same. And by using a resistor you can effectively change the way you drive them.
Of course, some times this is easy, and some times it is hard. Once you find the bad card, the restoration team likes to fix the bad card rather than just replace it. This can have its own challenges. I spent a long time trying to fix a card from the printer that ended up having a cracked trace that was intermittently bad. All the signals looked good, yet the card didn't work.
For a detailed look at a problem, I wrote a blog post about a core memory problem that turned out to be an inductor that failed open. After fixing that, the computer wouldn't power on. We replaced some weak transistors in the power supply, but that didn't help. Finally we found an undocumented fuse that had blown, probably from one of the boards we swapped. Replacing that got everything running again.
http://www.righto.com/2017/12/repairing-1960s-mainframe-fixi...
Anyway, thank you for those detailed information on the article.