I wonder what the theoretical limits to performance and usability of a 74xxx computer is. Email and chat should be possible as they were on 74xxx machines in the past, maybe even Gopher-style web browsing. But it's a hard sell when everyone's hooked on HD or even 4K video streaming.
But practically, the limits of a 74xx series in creating a 'modern feature' (like, 32-bit) CPU are manifold. Assuming DIP chips, it would pack an average of 4 logic gates in about 1 sq inch (hand-waving a bit, and including board space). A Cortex-M0 has approx 12,000 gates [1]. So it would be huge. Assuming LS logic, each chip would draw about 4.5mA peak, so about 13.5 amps peak. So it would use a lot of power. Propagation delay (maybe 10ns per gate in LS) means it will be much slower than integrated logic...perhaps a couple of orders of magnitude slower than an M0.
There are mitigations. You could use SMT packages and pack more on a board. You could use a more power-efficient logic family than LS (e.g. ALVT or some CMOS family). Or go for faster logic at the cost of power. But you're never going to get within an order of magnitude or 3 of the speed+efficiencies of a monolithic chip.
There are a number of homebrew TTL CPUs out there for comparison. Most are 4- or 8-bit.
[1] https://www.electronicsweekly.com/news/products/micros/arms-...
Now I know how to market it! "You're not doing real microservices unless you do it on the gate level!"
But it's cool that you have a working VAX. I've been wanting some kind of minicomputer for a long time, but if I could find a complete one I probably couldn't justify the cost.
Use someone's riscv soc: can you trust that company?
Use custom asic: do you trust the fab?
Use fpga: do you trust fpga vendor?
Use 74xx & SRAM: can be backdoor-ed too. Also provably Van Eck all the way to Fort Mede.
Use transistors: probably safe but will you finish that project in this lifetime ?
Not to mention that the compiler, synthesiser and all that software can be backdoor-ed too.
It's true that the battle can't be won, but that means it's a war of attrition. Backdooring 74xx chips would be very inconvenient and expensive compared to just pushing some code into the Intel ME or AMD PSP. The flip side of that is that building and using a 74xx computer is going to be just as inconvenient and expensive for the user. So this is more of a fun thought experiment than a serious solution.
https://archive.org/details/bitsavers_decpdp1111eb70_6917800
https://electronics.stackexchange.com/questions/260477/why-d...