AMD Returns To 1996 With Zen 5’s Two-Block Ahead Branch Predictor

An interesting finding in fields like computer science is that much of what is advertised as new and innovative was actually pilfered from old research papers submitted to ACM and others. Which is not to say that this is necessarily a bad thing, as many of such ideas were not practical at the time. Case in point the new branch predictor in AMD’s Zen 5 CPU architecture, whose two-block ahead design is based on an idea coined a few decades ago. The details are laid out by [George Cozma] and [Camacho] in a recent article, which follows on a recent interview that [George] did with AMD’s [Mike Clark].

The 1996 ACM paper by [André Seznec] and colleagues titled “Multiple-block ahead branch predictors” is a good start before diving into [George]’s article, as it will help to make sense of many of the details. The reason for improving the branch prediction in CPUs is fairly self-evident, as today’s heavily pipelined, superscalar CPUs rely heavily on branch prediction and speculative execution to get around the glacial speeds of system memory once past the CPU’s speediest caches. While predicting the next instruction block after a branch is commonly done already, this two-block ahead approach as suggested also predicts the next instruction block after the first predicted one.

Perhaps unsurprisingly, this multi-block ahead branch predictor by itself isn’t the hard part, but making it all fit in the hardware is. As described in the paper by [Seznec] et al., the relevant components are now dual-ported, allowing for three prediction windows. Theoretically this should result in a significant boost in IPC and could mean that more CPU manufacturers will be looking at adding such multi-block branch prediction to their designs. We will just have to see how Zen 5 works once released into the wild.

Carbon–Cement Supercapacitors Proposed As An Energy Storage Solution

Although most energy storage solutions on a grid-level focus on batteries, a group of researchers at MIT and Harvard University have proposed using supercapacitors instead, with their 2023 research article by [Nicolas Chanut] and colleagues published in Proceedings of the National Academy of Sciences (PNAS). The twist here is that rather than any existing supercapacitors, their proposal involves conductive concrete (courtesy of carbon black) on both sides of the electrolyte-infused insulating membrane. They foresee this technology being used alongside green concrete to become part of a renewable energy transition, as per a presentation given at the American Concrete Institute (ACI).

Functional carbon-cement supercapacitors (connected in series) (Credit: Damian Stefaniuk et al.)

Putting aside the hairy issue of a massive expansion of grid-level storage, could a carbon-cement supercapacitor perhaps provide a way to turn the concrete foundation of a house into a whole-house energy storage cell for use with roof-based PV solar? While their current prototype isn’t quite building-sized yet, in the research article they provide some educated guesstimates to arrive at a very rough 20 – 220 Wh/m3, which would make this solution either not very great or somewhat interesting.

The primary benefit of this technology would be that it could be very cheap, with cement and concrete being already extremely prevalent in construction due to its affordability. As the researchers note, however, adding carbon black does compromise the concrete somewhat, and there are many questions regarding longevity. For example, a short within the carbon-cement capacitor due to moisture intrusion and rust jacking around rebar would surely make short work of these capacitors.

Swapping out the concrete foundation of a building to fix a short is no small feat, but maybe some lessons could be learned from self-healing Roman concrete.

The Flash Memory Lifespan Question: Why QLC May Be NAND Flash’s Swan Song

The late 1990s saw the widespread introduction of solid-state storage based around NAND Flash. Ranging from memory cards for portable devices to storage for desktops and laptops, the data storage future was prophesied to rid us of the shackles of magnetic storage that had held us down until then. As solid-state drives (SSDs) took off in the consumer market, there were those who confidently knew that before long everyone would be using SSDs and hard-disk drives (HDDs) would be relegated to the dust bin of history as the price per gigabyte and general performance of SSDs would just be too competitive.

Fast-forward a number of years, and we are now in a timeline where people are modifying SSDs to have less storage space, just so that their performance and lifespan are less terrible. The reason for this is that by now NAND Flash has hit a number of limits that prevent it from further scaling density-wise, mostly in terms of its feature size. Workarounds include stacking more layers on top of each other (3D NAND) and increasing the number of voltage levels – and thus bits – within an individual cell. Although this has boosted the storage capacity, the transition from single-level cell (SLC) to multi-level (MLC) and today’s TLC and QLC NAND Flash have come at severe penalties, mostly in the form of limited write cycles and much reduced transfer speeds.

So how did we get here, and is there life beyond QLC NAND Flash?

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Retrotechtacular: The Tools And Dies That Made Mass Production Possible

Here at Hackaday we’re suckers for vintage promotional movies, and we’ve brought you quite a few over the years. Their boundless optimism and confidence in whatever product they are advancing is infectious, even though from time to time with hindsight we know that to have been misplaced.

For once though the subject of today’s film isn’t something problematic, instead it’s a thing we still rely on today. Precision manufacturing of almost anything still relies on precision tooling, and the National Tool and Die Manufacturers Association is on hand in the video from 1953 below the break to remind us of the importance of their work.

The products on show all belie the era in which the film was made: a metal desk fan, CRT parts for TVs, car body parts, a flight of what we tentatively identify as Lockheed P-80 Shooting Stars, and a Patton tank. Perhaps for the Hackaday reader the interest increases though when we see the training of an apprentice toolmaker, a young man who is being trained to the highest standards in the use of machine tools. It’s a complaint we’ve heard from some of our industry contacts that it’s rare now to find skills at this level, but we’d be interested to hear views in the comments on the veracity of that claim, or whether in a world of CAD and CNC such a level of skill is still necessary. Either way we’re sure that the insistence on metrology would be just as familiar in a modern machine shop.

A quick web search finds that the National Tool and Die Manufacturers Association no longer exists, instead the search engine recommends the National Tooling And Machining Association. We’re not sure whether this is a successor organisation or a different one, but it definitely represents the same constituency. When the film was made, America was at the peak of its post-war boom, and the apprentice would no doubt have gone on to a successful and pretty lucrative career. We hope his present-day equivalent is as valued.

If you’re of a mind for more industrial process, can we direct you at die casting?

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Taking A Look Underneath The Battleship New Jersey

By the time you read this the Iowa-class battleship USS New Jersey (BB-62) should be making its way along the Delaware River, heading back to its permanent mooring on the Camden waterfront after undergoing a twelve week maintenance and repair period at the nearby Philadelphia Navy Yard.

The 888 foot (270 meter) long ship won’t be running under its own power, but even under tow, it’s not often that you get to see one of the world’s last remaining battleships on the move. The New Jersey’s return home will be a day of celebration, with onlookers lining the banks of the Delaware, news helicopters in the air, and dignitaries and veterans waiting eagerly to greet her as she slides up to the pier.

But when I got the opportunity to tour the New Jersey a couple weeks ago and get a first-hand look at the incredible preservation work being done on this historic ship, it was a very different scene. There was plenty of activity within the cavernous Dry Dock #3 at the Navy Yard, the very same slip where the ship’s construction was completed back in 1942, but little fanfare. Staff from North Atlantic Ship Repair, the company that now operates the facility, were laboring feverishly over the weekend to get the ship ready.

While by no means an exhaustive account of the work that was done on the ship during its time in Dry Dock #3, this article will highlight some of the more interesting projects that were undertaken while it was out of the water. After seeing the thought and effort put into every aspect of the ship’s preservation by curator Ryan Szimanski and his team, there’s no doubt that not only is the USS New Jersey in exceptionally capable hands, but that it will continue to proudly serve as a museum and memorial for decades to come.

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When Your Rope Is Your Life

Climbers care a lot about their ropes because their lives literally depend on them. And while there’s been tremendous progress in climbing rope tech since people first started falling onto hemp fibers, there are still accidents where rope failure is to blame.

This long, detailed, and interesting video from [Hard is Easy] follows him on a trip to the Mammut test labs to see what’s up with their relatively new abrasion-resistant rope. His visit was full of cool engineering test rigs that pushed the ropes to breaking in numerous ways. If you climb, though, be warned that some of the scenes are gut-wrenchingly fascinating, watching the ropes fail horribly in well-shot slow-mo.

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Tech In Plain Sight: Theodolites

We take it for granted that you can look at your phone and tell exactly where you are. At least, as exact as the GPS satellites will allow. But throughout human history, there has been a tremendous desire to know where here is, exactly. Where does my farm end and yours start? Where is the border of my city or country? Suppose you have a flagpole directly in the center of town and a clock tower at the edge of town. You know where they are precisely on a map. You also know how tall they are. What you need is a theodolite, which is an instrument that measures angles very precisely.

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