Hacker News new | ask | show | jobs
by amelius 166 days ago
> What a clueless post. Even ignoring their massive overstatement of the difficulty and hardware complexity of hardware mapping tables, they appear to not even understand the problems solved by mapping tables.

From the article:

> And before you tell me this is impossible: The computer is in the next room, built with 74xx-TTL (transistor-transistor logic) chips in the late 1980s. It worked back then, and it still works today.
3 comments
loeg 166 days ago
Do you think a 1980s computer has no drawbacks compared to 2020 vintage CPUs? It "works..." very slowly and with extremely high power draw. A 1980s design does not in any way prove that the model is viable compared to the state of the art today.
link
Veserv 166 days ago
I did not say it was impossible. I said that mapping tables solve a lot of problems. There are very good reasons, as I explicitly outlined, for why they are a good solution to these classes of problems and why object stores fall down when trying to scale them up to parity with modern designs for general purpose computing.

People tried a lot of dead-ends in the past before we knew better. You need a direct analysis of the use case, problems, and solutions to actually support a point that a alternative technology is better rather just pointing at old examples.

link
IshKebab 166 days ago
A lot has changed since the 1980s. RAM access is much higher latency (in cycles), we have tons more RAM, and programs use more of it.

Maybe it is still possible but "we did it in the 80s so we can do it now" doesn't work.

Vypercore were trying to make RISC-V CPUs with object-based memory. They went out of business several months ago. I don't have the inside scoop, but I expect the biggest issue is that they were trying to sell it as a performance improvement (hardware based memory allocation), which it probably was... but also they would have been starting from a slower base anyway. "38% faster than linear memory" doesn't sound so great when your chip is half as fast as the competition to start with.

It also didn't protect objects on the stack (afaik) unlike CHERI. But on the other hand it's way simpler than CHERI conceptually, and I think it handled temporal safety more elegantly.

Personally I think Rust combined with memory tagging is going to be the sweet spot. CHERI if you really need ultra-maximum security, but I think the number of people that would pay for that is likely small.

link