I'm not actually aware of any CPUs that preform a XOR faster than a SUB. And more importantly, they have identical timings on the 8086, which is where this pattern comes from.
I'm studying 4-bit-slice processors from the 1970s. This is all tangent to the x86 discussion. Minicomputer processors!
I have two bit-slice machines from TI based on the 74S481 (4-bit slice x 4).
Just like with the 74181, all ALU operations go through the same path, there are just extra gates that make the difference between logical or arithmetic. For instance, for each bit in the slice, the carry path is masked out if logical, but used if arithmetic.
* The XOR operation (logical) is accomplished with A+B but no bits carry. If carry is not masked, you get arithmetic ADD.
* The ZERO or CLEAR operation is (A+A without carry). With carry, A+A is a shift-left.
* The ONES operation forces all the carry chain to 1 (ignoring operand) (you can do a ONES+1 to get arithmetic 0, but why?)
* In the simpler 74181 (4 years earlier) there are 16 operations with 48 logical/arithmetic outcomes. Pick 12 or so for your instruction set. There are some weirdos.
The crazy thing here is that in the TM990/1481 implementation, the microinstruction clock is 15 MHz, and each has a field for number of micro-wait states. This is faster than the '481s max!
Theoretically, if 66ns is sufficient to settle the ALU, a logical operation doesn't need a micro-wait-state. While arithmetic needs one, only because of carry-look-ahead. If I/O buses are activated, then micro-instructions account for setup/hold times. I could be wrong about the details, but that field is there!
It's the only architecture I know of with short and long microinstructions! (The others are like a fixed 4-stage cycle: input valid, ALU valid, store)
Thanks, I suspected there might be something from the minicomputer era.
I've only really looked at a single AM2900 implementation (and it was far from optimal). Guess I need to dig deeper at some point.
> The ONES operation forces all the carry chain to 1 (ignoring operand) (you can do a ONES+1 to get arithmetic 0, but why?)
Forcing all carries to 1 inverts the output.
If I'm understanding the ALU correctly, (the datasheet doesn't show that part) it only implements OR and XOR. When combined with the ability to invert both inputs, AND can be implemented as !(!A OR !B), NAND is (!A OR !B) and so on.
Or maybe the ALU implements NOR and XNOR, and all the carry logic is physically inverted from what the documentation says.
Population density is one thing. Another issue is timing.
New Zealand was a really young country when railway technology came along, and didn't really have enough time or money to invest in a good railway network before other technology came along.
Airplanes are the perfect technology for NZ's geography, because they just fly over everything. There are actually a few places in NZ that received passenger airline service in the 30s before they received a railway connection (namely Gisborne), and many other places that never received railway connections.
At the same time, NZ was one of the fastest adopters of the automobiles, second only to America.
I think viable cars and airplanes had taken another 25 years to arrive, NZ might have had a much more complete railway network, with a much better chance of surviving intact into the modern era.
Didn't know about these historical facts, looks like timing really contributed to the current situation in New Zealand. When I was in Auckland some years ago, I remember NZ trying to bring some railway services back, before the pandemic.
I never got to travel on these, but I'm hoping to do that when I'm there again, probably next year. I see the website is still the same, so if anyone is going to NZ: https://www.greatjourneysnz.com/.
And to be fair, looks like you can more or less cross the country, as long as you don't plan to get all the way to Invercargill.
The railway services NZ are trying to bring back are regional commuter services. Auckland to Hamilton (now in operation); Auckland to Tauranga; Wellington to Palmerston North (Capital Connection, has been in operation for 35 years, about to be upgraded to battery-electric trains, since only half the route is electrified).
And also the vague idea of local rail service around Christchurch (interestingly, a private company bought the old DMUs from Auckland's local fleet after electrification and are just starting to run special trains for Rugby games).
Part of the problem is that there is only really only three metro areas in New Zealand. Auckland, Wellington and Christchurch. Everything else isn't really large enough to provide enough demand for a proper intercity route. And Christchurch isn't even on the same island, so you can't have a proper intercity train with the ferry getting in the way.
So the only potentially viable intercity route is Auckland to Wellington.
And apart from Hamilton and Palmerston North, (which already have commuter trains) there is absolutely nothing in the middle. The same distance in Europe or the US's eastern corridor would service 4-6 decently sized metro areas, and provide plenty of extra demand.
There just isn't enough potential demand to put a high-speed rail line through there. And without the high-speed rail, it's a 10 hour train trip that has zero chance of competing with a 1 hour plane ride.
Christchurch to Wellington is even worse. 6 hour train ride, at least an hour waiting for the ferry, 3.5 hour ferry ride. The plane does it in at little as 25 min in the air, there isn't enough time to reach cruising altitude. There is a reason why the route used to be serviced by an overnight ferry.
> And to be fair, looks like you can more or less cross the country, as long as you don't plan to get all the way to Invercargill
Yeah... but those aren't "intercity trains". They are scenic tourist trains that just so happen to be running along old intercity routes. Not bad as a tourism experience, but overpriced and not optimised for transportation needs.
The fact that you can't book both the Interislander ferry and costal pacific on the same website is very telling. They are literally run by the same company.
Same company that's providing the Rugby special trains, but this is using the old Capital Connection rolling stock. The train usually runs day trips up to Arthur's pass for cruise ships, but when there is a gap in that schedule they are running these Christchurch to Dunedin and Christchurch to Invercargill excursions.
I remember the announcement some years ago of the Auckland-Hamilton train. I think initially it had limited schedule, but from what I recall the usage was quite good after the launch (I think it was before or just after the pandemic). Good to know it's in operation now.
> And also the vague idea of local rail service around Christchurch (interestingly, a private company bought the old DMUs from Auckland's local fleet after electrification and are just starting to run special trains for Rugby games).
Hadn't heard about this! Interesting, and good idea to have a service for the games.
> So the only potentially viable intercity route is Auckland to Wellington.
This one would probably be quite busy. I had to fly Auckland-Wellington quite a bit as an engineer, and our managers & executives travel quite more (NIWA, a CRI that now I believe has merged with another one and changed its name).
Eventually I had to go to the capital to vote or for the embassy, or for a tech event. All these trips were always via airplane, but I'd be happy to get a fast train or a night train as in Europe.
Learned another new thing, thank you! I plan to go to Invercargill when I visit again to see if I can see the Aurora Australis or maybe check out where they have the MetService radiosonde launch. From what I recall MetService used to launch one from Invercargill near the airport (or I could be confused with a weather station or another climate monitoring station they had there).
What about options for those living up north? When I was still in Auckland some of my co-workers were looking into moving further West/North (there were too many people moving to South Auckland/Raglan/Hamilton at that time). But I remember the transport options involved one or more buses, and a ferry in the case of a co-worker that bought a house in... Hobsonville I believe. But the ferry didn't run all days, and had a limited schedule compared to the one for Waiheke or Devenport. Has that improved?
I always thought it'd be nice if there was a short train line connecting Devenport to Cape Reinga, as all the times I went to Cape Reinga or to take someone to Russel I'd have to drive or find a private shuttle.
I agree that if you put a high-speed line between Auckland and Wellington, and get the travel time down to 3-4 hours, people would use it. It would actually be faster than going to the airport for central Auckland, or anything further north.
But high speed lines are expensive, and NZ just doesn't have anywhere near the population density to justify it.
As for night trains, I'm pretty sure they can only exist where they are bridging multiple viable day train routes. Which is why that huge gap between Hamilton and Palmerston North is an issue.
And the route might actually be a bit short for a night train. If they electrified the entire distance (instead of using a diesel the whole way despite the fact 80% of the route is electrified) and did some improvements, they could probably get it down to an 8 hour trip.
> What about options for those living up north?
TBH, I'm not a fan of Auckland and don't really know what's going on with local public transport.
> If I hand wrote some notes in a notebook or diary, I wouldn't have to hand them over, as I understand it, even with no lawyer in the mix. Same if I wrote some notes in a text file on my computer.
There is some protection of personal private documents for civil cases. But for a criminal case, there is no 4th or 5th amendment protection for stuff you wrote in your diary.
If you were caught with notebooks detailing your plans to kill a list of people, showing that you've meticulously tracked their movements and listing locations for dumping the bodies that would be extremely relevant. I don't see how it'd be a good idea to exclude that kind of evidence.
The point of the checksum is to just drop obviously wrong keys. No need to handle revocation or do any DB access if checksum is incorrect, the key can just be rejected.
You don't have to use a publicly documented checksum.
If you use a cryptographically secure hashing algorithm, mix in a secret salt and use a long enough checksum, attackers would find it nearly impossible to synthesise a correct checksum.
I don't follow. The checksum is in "plain text" in every key. It's trivial to find the length of the checksum and the checksum is generated from the payload.
Others have pointed out that the checksum is for offline secret scanning, which makes a lot more sense to me than ddos mitigation.
But it's trivial to make a secret checksum. Just take the key, concatenate it with a secret 256-bit key that only the servers know and hash it with sha256. External users might know the length of the checksum and that it was generated with sha256. But if they don't know the 256-bit key, then it's impossible for them to generate it short of running a brute force attack against your servers.
But it does make the checksum pretty useless for other usecases, as nobody can verify the checksum without the secret.
Aren't astronomy problems almost exactly the opposite?
In astronomy the background is mostly static, providing an excellent reference frame either when trying to discover/track a moving object, or when trying to overlap multiple images of the same object for better observations.
If you're looking for an unknown island your background is constantly changing, but you're looking for something which is somewhat static but might not actually exist.
It's just really easy to do accidentally with custom allocators, and games tend to use custom allocators for performance reasons.
The system malloc will return pointers aligned to the size of the largest Atomic operation by default (16 bytes on x86), and compilers depend on this automatic alignment for correctness. But it's real easy for a custom allocator use a smaller alignment. Maybe the author didn't know, maybe they assumed they would never need the full 16-byte atomics. Maybe the 16-byte atomics weren't added until well after the custom allocator.
The model is probably legitimately better. But it might not be enough better to justify the extra cost of inference.
They know if they released it publicly, people will be able to see exactly how smart it is, and adjust their demand correspondingly. Anthropic will either need to price it high enough that nobody uses it (and the hardware is sitting mostly idle to servicing a few customers), or lower their profit margins (potentially below cost) to price it fairly.
So instead, they bundle it with this fancy new exploit finding scaffold, and sell the combined it to enterprise customers. I bet the scaffold works fine with smaller models, but gets notably improved results with Mythos.
The two products support each-other, and with the exclusive bundle Anthropic can get more profit selling both together than they would get selling them individually.
And as an added bonus, people over estimate the capability of this unreleased model, providing hype for Anthropic.
One is a quick summary of the current balance in a channel. A new transaction is created each time the balance in the channel changes. It's somewhat cheap to put on the blockchain (And the main saving is that you only need to post the final update when you close the channel), but venerable to one side putting an old stale transaction onto the blockchain to profit.
The other transaction forms a chain of proof for current state, invalidating previous balance update transactions. It's somewhat expensive to post, as it will pull in the whole history.
Both peers need to continually watch the chain (or contract a 3rd party to watch) to make sure the other peer isn't cheating by posted a stale balance transaction. These special transactions are time locked, so once one is posted, you have like 24 hours to post the proof transaction and reverse it.
They are suggesting bypassing the RP2350's internal switching regulator (which only needs an external coil and some caps) and replacing it with an external linear regulator (which is actually supported by the datasheet)
Switching regulators have much lower power draw (which is important when running off batteries) and generate less heat, which sometimes leads to a more compact footprint (though I'm not sure the RP2350's core uses enough power for that benefit to kick in)
The power/heat savings don't really matter for this usecase, and linear regulators have the advantage of producing more stable power, though you are hardwiring it to 1.2v (a small overvolt) rather than using the ability of the internal regulator to adjust its voltage on the fly (adjustable from 0.55c to 3.30v)
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