BeagleV-Ahead RISC-V board
beagleboard.org
beagleboard.org
I'd love to see a RISC-V SoC (not just a dinky little MCU) that has real / complete documentation. So far I have yet to find any for any of the various RISC-V based SBCs that have shipped.
As far as I can see, the only thing that isn't documented is the DDR startup/training code, which is a binary blob in u-boot. There are a few registers that are undocumented which need to be set to start up but I think the rest is well documented.
https://www.sifive.com/documentation
In addition to a documented RV64 SoC, it'd be cool to see some RV32 MCUs that are a little beefier -- more competitive with the mid-range Cortex M4 and M7 stuff (more peripherals, more SRAM, etc) -- instead of the existing stuff that looks similar to very tiny M0/M3 devices.
Was the idea of an open ISA leading to an open SoC was just wishful thinking?
RISC-V (and SiFive) caught a moment where it could be used is a way to squeeze ARM on pricing. It doesn't really meaningfully create openness on the interesting parts of the stack (core architecture, SoC architecture, etc.) on its own. In that sense, the hype is overblown.
It does _enable_ open-source cores to some degree, but that's it, someone has to take the leap to make a production-ready one. A few companies are trying, but an open-source SoC is even further down the road.
https://github.com/T-head-Semi/openc910
The same cores are used in the 64 core SG2042 workstation/server SoC.
RISC-V was sold to us as the fully open CPU ecosystem but all it offered was an open design and some reference implementation in Chisel. That is not much different from MIPS which opensourced some CPUs 10-15 years ago.
A lot more is needed for a fully open RISC-V computer.
It simply allows for open source implementations to exists.
> but all it offered was an open design and some reference implementation in Chisel
You are confused between what RISC-V the foundation and what different people in the ecosystem do. RISC-V was started by Berkley and then they created a foundation. There are NO REFERENCE Implementation! Not in Chisel or anything else. Chisel is simply what Berkley used for some of their initial work.
And it has largely worked. There are lots of high quality open CPUs. This was certainty not the case in the past:
- https://www.openhwgroup.org/
- https://www.chipsalliance.org/
There are many more.
> That is not much different from MIPS which opensourced some CPUs 10-15 years ago.
Its very different because you were not allowed to use those MIPS chips or built products with it. The only one that was as open was SPARC 32-bit.
What we don't have is cheap mass produced SoC that are well documented. But that a general problem of the industry not just RISC-V.
The boot process for RISC V is standardised. There are going to be far more RISC-V SBCs that support uefi than ARM SBCs.
ARM addressed this by creating ATF which most companies now use:
https://git.trustedfirmware.org/TF-A/trusted-firmware-a.git/
Last time I wanted rs-232 specs of a solar inverter, took me months to contact them and after some persuasion, a guy emailed me an NDA I had to physically print, sign, scan and send them back before they gave me a copy.
Obviously I was feeling funny so I signed Johnathan doe and they send me the file.
Turns out, that file was readily available online in forums because others had done the same thing.
So much for NDA. Sigh
Their proprietary driver will stay closed, but hopefully they'll be able to deprecate it at some point.
I find the most useful there is the JH7110 TRM specifically.
There's links to a bunch more over here[1].
0. https://doc-en.rvspace.org/
1. https://forum.rvspace.org/t/visionfive-2-faq-quick-links/137...
I find the most useful there is the JH7110 TRM specifically.
There's links to a bunch more over here[1].
0. https://doc-en.rvspace.org/
1. https://forum.rvspace.org/t/visionfive-2-faq-quick-links/137...
The Beagle hardware is great but it seems to me they just don't have the resources or focus to support the hardware they release.
Anyway I was thinking about buying it, but ended up with buying Nvidia's Jetson instead, due to software and documentation difference.
Jetson has a big edge in software and documentation, no doubt. Poor documentation and SDKs seems to be the norm for a lot of embedded processors, especially for the AI acceleration piece.
I’m curious for this new beagle board if there’s enough documentation / software to use the AI accelerator.
It's nice to see the project still chugging along
For example, A BeaglePlay costs about twice what a Pi 4 Model B/4GB does in my local market. The BeaglePlay has half the ram, only one USB 2 port to the Pi's two, none of the Pi's USB 3 connectors, way fewer GPIOs, only one HDMI, no audio, etc. I do like that BeagleBoards have onboard flash though.
Nowadays, there are fast hobbyist-accessible microcontrollers with USB or wifi support that can fill a lot of the same niches, so I think they sorta missed the boat.
Beagleboards are just different than RPis. They aren't really trying to be the same thing. RPis are small computers with simple GPIO meant for turning on and off things, Beagleboards are computer/microprocessor hybrids with GPIO meant for doing realtime I/O.
The soc on the original Black had two 200MHz PRUs which ran independently of the main processor and could be used for signalling and sensing tasks that require tight timing guarantees, and can then trigger interrupts on the main CPU.
RP2040's PIO is extremely limited with only 9 available instructions, this looks a bit more involved, but functionally it's very similar.
edit: also Ti's PRU has been around waaaay longer than the RP2040 so the PRU is likely an inspiration for the PIO.
Yeah agreed, and I don't think I communicated that in my comment above. It's not that the Pi is universally better in all cases, but it is better suited for many common consumer applications... Which logically leads to it being the higher selling device.
Maybe you didn't mean this in a way to diminish how handy Raspberry Pis are, but I've used it in tons of situations that are more interesting than turning LEDs on and off. It being a usable computer is icing on the cake. I have RPis for all kinds of things: Home Assistant using the Bluetooth module (+ external Z-wave/Zigbee controller via USB), OpenJVS for running arcade I/O emulation (GPIO for serial communication), I doubt I need to explain how useful it is to have a FlashROM setup, I've gotten a Pi to drive a Commodore SID...
I can see based on the RPi Pico which seems to have similar functionality to the Beagleboard in terms of I/O that in fact there is so much more that COULD be done, and I'm glad that we have these now. That said, I don't want people to think that RPi is a toy! Having a moderately powerful small form factor computer connected to all of this I/O lets you do things that you couldn't even when GPIO is involved. Not to mention, you can bitbang the GPIO really fast on a Raspberry Pi, which can come in handy.
That said, I've seen some neat shoestring-budget prototype projects done on BB hardware, so there's some market there. But it seems like their stuff is a bit expensive for low-end learners and hobbyists and missing some of the niceties you get if you convince your boss to buy a ComExpress-based industrial module, or (if you really twist their arm) something like the Arnouse BioDigital SBCs.
IF you can actually get one. That's a REALLY big IF.
RPis have been subsidized for a long time. The fact that the subsidy is gone means that they don't seem to be willing to release them to we plebians very much anymore. They're fine releasing them to T-Mobile, though.
Anybody not a pure hobbyist left the RPi space long ago.
Actually, the constrained supply is because during COVID and aftermath they decided to support industrial customers to the detriment of hobbyist supply.
They're currently cranking out a million units per month and supply is returning to retail. https://rpilocator.com/ was completely bare a few weeks ago, and now there's a lot of retailers with stock (though it's still not where it should be).
I think this month it really shifted from "trickling availability" to full deluge. Right now people like me who've wanted one but have been holding off are finally making our purchases. Once that appetite is filled, I can imagine we'll just see some places with steady stock.
Still waiting on CM4 though. Those are still backordered and out of stock most places.
I suspect a lot of hobbyists have left too, and that's why there's so many not-quite-knockoff SBCs on the market (ranging from the respectable OrangePis to weird fly-by-night stuff on AliExpress made by a company that's already out of business before your order arrives).
But I don't know how many people are using alternatives because they want to use alternatives. Raspberry Pis have been like hen's teeth for a couple of years now. If you have a NIB Pi4, until recently you could sell that sucker and probably by 3 OrangePis instead.
But if RPis were the same price? I think they'd sell like hotcakes just like they did a few years ago, and you'd see them in every random project on Youtube. I don't know of any SBC (other than very high-end industrial embedded modules) that are as well-documented as the Pis.
I'm not sure the Pico and Pico W are going to make as much of a splash as the original did (it's harder for people to get started with an overgrown microcontroller than it is a tiny PC), but I expect them to sell very well, too. Maybe they won't show up in every disposable pregnancy test and lightbulb like the ESPs and Nordics, but I suspect we'll see them in some commercial products too.
Over the pandemic, started using more of the mini intel boxes in the sub-$300 space, just because of availability and price gouging.
https://github.com/RobertCNelson/omap-image-builder
I believe Robert is an applications engineer with Digikey; he does stellar work on this, thank you RCN!
Does it have Linux kernel support in the mainline? I.e., not some weird semi-proprietary patch blob on some GitHub account basing of the 3.18 kernel or so..
If it doesn't, I can close the tab immediately and know for sure that I won't miss out. If it posted patches to the LKML, maybe even in an advanced revision integrating review comments then it might be worth looking at it later.
In any event, VF2 is the best option currently, if you wish for a board that cares about upstream support and, in general, just works.
I've been down this road and while it was certainly an interesting learning experience in some of the mechanics of the kernel build process, module dependencies, etc. etc., it was not necessarily productive in moving the projects forward that I wanted to do with the temptingly-cheap Chinese SBCs that I couldn't resist buying.
Having learned that lesson, now I won't order something unless it's formally supported by someone like the Armbian project (or Debian, or OpenWRT, etc.). And as interesting as some of the niche SBCs are, sticking to boards that have a broad userbase saves a lot of time when you run into weird errors.
I used to scoff at PowerVR GPUs as being unsupportable & worthless, but progress has been quite good lately. Only 3 SoC supported & not this but porting should go relatively smoothly now.
Price feels high.
Elephant in the room: what the heck is that USB micro 3.0 connector doing there? Yikes! What an ugly relic. And that's the only USB on the board.
On the original beaglebone and beaglebone black, a nice feature is you can connect it by microusb, and this provides power to the board but also bridges your internet connection. So with one cable you get power, ssh into the device, and an internet connection on the device.
It is however way way way lower level than VisionFive 2. Beaglebone was an embedded system you didn't even have to know cli to be able to use. Self hosting a networking gadget + whole web based ide for itself, either back at launch in 2008 or even today, was an amazingly friendly feat.
Note there's several, by different vendors, with different connectivity (e.g. PCIe, M2, wifi/bt) and RAM (4-16GB range).
The CPU is a XuanTie C910, which is somewhat faster than SiFive U74 used in the JH7110 (VisionFive2), and adds pre-spec vector extension (0.7.1).
I would still recommend VisionFive2 or Star64 to most people, due to its maturity and much better upstream support[0].
Is there any confidence to be had from the well established nature of Beagle Bone (whoever the corporate master is).
I am entirely unfamiliar with Beagle Bone, so a genuine question
What's true is VisionFive2 is from StarFive, and so is the JH7110, and they seem to care about and understand the value of the software ecosystem, which is why VF2 exists at all.
Whereas Beaglebone is not involved in TH1520.
Whereas VisionFive2 is a means for Starfive to leverage the community to accelerate support, while at the same time giving them a compelling SBC.
Every time I opted for cheaper clone of beagleboard or RPi I ended up regretting it when I inevitably had to spend hours building custom kernel patches and struggling to get it working reliabily. The more expensive boards usually work out of the box with mainline kernel.
For some that can be worth the extra $50.
I'm just hesitant to buy one of those without having some 3rd party confirm everything works well out of the box, and the more obscure the device the harder to find such accounts.
Every goddamned RPi-like SBC seems to require a very, very specific version of the Linux kernel that has been patched to hell and back. Almost always bundled with binary blobs/firmware that only work with that very specific version of the kernel.
None of these patches get upstreamed and the binary blobs/ultra proprietary who-knows-wtf-its-doing required firmware never get updated after the release. This means that you'll be stuck with whatever version of the kernel that shipped with the device forever. Complete with all the bugs and vulnerabilities that get discovered later.
Never again! Either the vendor needs a history of staying on top of things or they need to make some serious promises about upstreaming kernel patches and drivers.
Example of a terrible SBC vendor you should never buy from: Orange. All the OrangePi SBCs are exactly as I described. You can expect any bug or security issue that exists at release to be a problem with that board forever. They will never get fixed. They might release an update or two within a few months of release (if it's real bad) but that's all you'll ever get.
They ALL suck, some just suck less than others. Broadcom, Renesas? The worst. ST, NXP, TI? Slightly better than fully sucking. Look to the chipmaker (ST, NXP) and not the board maker (Orange) for a guide in how well things go.
From experience I agree with you, the chipmakers suck because they utterly fail to be open source when they're one of the groups that needs it the most. It is to the extent that I would advocate for laws in the theme of right-to-repair to force chip vendors to provide source for necessary code to use their products to consumers. (in this case open source in the narrowest definition, they can keep their copyrights but would be required to distribute source to end users in a form and with a license that makes them usable)
If the question is "are any of the SBCs worth the trouble?" and the default answer is no unless I have a really good reason and want to dedicate the time to building the janky software stack (I don't), or they're from a small list of vendors I'd trust won't be a mess (RPi, nvidia, beagle, ... that's it off the top of my head)
The real question is if Broadcom is devoting internal software resources to improving the ecosystem, or if it's coming from the devoted users. I don't track commits on kernel.org enough to know what's what.
As someone that has worked with these EVKs for decades, you never treated them as part of your final product. But with the advent of Beagle and RPI, that's where we are now.
But when you buy an RPi or Beaglebone as the core of your industrial smelter and expect support for that module comparable to, say, a module from Kontron? You're going to be disappointed.
You move off that kernel version, no BSP, no boot. sad times.
This is one reason why you don't get android phones supported past the android release shipped.
You're completely at the mercy of the SoC provider. Promises of 'n' years support are quite often quietly dropped after 18 months, when they realise all the engineers have moved to working madly to get the latest SoC's BSP out of the door.
Rinse and repeat.
Hopefully Fuchsia’s stable ABI promises pan out and companies start releasing drivers for it.
Haiku remarkably does have proper driver APIs and stable ABIs.
Linux is and will remain painful, on all platforms, until it is finally deprecated, and for a while longer after that.
The idea here would be to run things like the TCP stack, USB from the lowest proxy-able level the in USB stack, etc in the guest kernel(s), as well as the entire application level, so as to reduce exposure to vendor kernel bugs and feature freeze leaving it only with minimal SOC-specific nitty gritty. For GPIO the vendor kernel could be used as a PRU of sort, passing messages to the guest kernel for actual processing.
Then the vendor kernel is just treated as a BIOS/blob getting in the way as little as practicable, it's very ugly but would allow using all these boards, also same method could possibly be used to recycle obsolete android phones.
Some of the real issues are as follows:
1) Most companies use Debian as a base. Debian has a notoriously slow release cycle. This means it takes loads of time to submit patches -> get approval -> get merged in a merge window -> wait for debian to use new kernel with new code.
2) The GPU situation is a mess. No decent (compatible) vendors with open source GPU drivers exist. Imagination is said to be working on open source drivers, but with no real release date, we are stuck using closed source blobs. Once drivers and Mesa get updated, we then have to wait for a new release of Debian to pick these up.
3) Far fewer people use these boards over a Raspberry Pi. This means community support takes longer to develop. The VF2 has other distros like Arch and Ubuntu, for example, but no real active community behind them. Last I checked, hardware GPU acceleration was not working in these distros.
Vision Five 2 it is then
They seem to have basically outsourced their software maintenance to Armbian, and if that relationship holds it's probably a win-win. Armbian's build system is really nice, IMO.
FriendlyElec are borderline; they make nice hardware but definitely seem to take a "here's a kernel we got to boot once, good luck!" attitude towards software support. Some of their boards are supported by Armbian but often without key features due to lack of documentation or binary blobs.
Below that is a vast sea of largely-anonymous Chinese-based hardware companies who drop a design (sometimes really neat) into the world, then disappear without a trace. Mostly I think these are designs whipped up quickly to use up spare parts, or originally designed for embedded use in a particular product and being sold on the side. (I've definitely seen 'development boards' that were clearly designed for security cameras or TV decoder boxes, f.ex.) But you are buying yourself a new hobby if you decide to get one.
The reason I'd buy a Beagle (well, really an ESP32) isn't the price, it's the convenience of havng real time GPIOs.
The SoC had quad C910 OoO cores (similar to A72) as the application processors. There is also a simple E902 (in-order, 2 pipe stages, RV32EMC ... basically Cortex M0 equiv) in the Always-On subsystem and a C906 (64 bit in-order, 5 pipe stages, used as main applications processor in numerous AllWinner D1, Bouffalo BL808 etc boards) in the "audio" subsystem.
Looks like this board (if you mean https://linuxgizmos.com/dev-kit-debuts-risc-v-xuantie-c910-s... or something like it) runs Linux (android or debian). With the BB, you could at least program the PRUs to handle these problems directly in hardware. With the ESP32 you're writing code that runs in an RTOS. Most SBCs I've seen make you use userspace to access GPIOs. unfortunately for my use case, I have about a 100 nanoseconds to move a signal from one GPIO to another, and if I drop an interrupt, it means part of my data ends up missing.
Why would I be talking about the RVB-ICE? They use the same main CPU cores, but a totally different SoC.
The TH1520 has, as I wrote in my last post, two secondary RISC-V CPUs that are not managed by Linux, and which can be used for real-time tasks.
Of course you don't HAVE to run Linux in the first place if you don't want to. RISC-V chips are very standardised and easy to program bare-metal. The only tough part is usually DRAM and clocks initialisation. You can use the board's standard U-Boot SPL for that if you want, then either replace the Linux kernel by your own code, or also replace the higher level part of U-Boot.
The datasheet doesn't mention Vector (V) extension support. Is this an error on the Beagleboard page?
You might see poor price/performance EVBs with RVV 1.0 in 2024, e.g. $500-$1000+ with similar specs to this.
I don't think you're going to see anything like a quad core 2.0 GHz OoO (with 2 OoO vector pipelines) board with RVV 1.0 for $150 until 2026 at the earliest.
The dimensions are different (more square, more USB ports, no GPIO) but they're not as big as you may think. A NUC is about twice the size of a Beaglebone with much better performance and software support, plus the advantage of being able to pick your own RAM and storage options.
For something like a picture frame you can easily use a NUC. For an e-reader you'd run into form factor issues for the cooler, but for something that low spec an ESP32 would be even more compact without sacrificing much.
I have quite a few NUCs, and they are awesome. It's a shame Intel is getting out of the platform. But, for the money this one I got last week is incredible. It's surprisingly fast and runs on the smallest plugpack I ever saw for a full PC (and it's probably hollow).
Running Linux of course. Installed Bookwork and everything works.
1: https://www.amazon.com/GMKtec-Nucbox5-Desktop-Computer-Windo...
Also, check this out: https://www.amazon.com/GMKtec-Nucbox5-Desktop-Computer-Windo...
https://www.arrow.com/en/research-and-events/videos/comparin...
At the moment I have no plan to acquire yet another beagleboard, i.e. this BeagleV, a bit pricey for potential projects at scale, and I don't need those media related ports, though the AI NPU seems nice for edge AI.
H.265/H.264: Where is AV1? Coze risc-v is worldwide royalty free, not h.265/h264.
HDMI: same issue than H.265/H.264, I should see a dedicated display usb-c connector (displayport).
But I am being excessive, it is going in the right direction, the next step is to remove H.265/H.264 and HDMI royalties.
That said, has the GPU a lean, plain and simple C written, vulkan3D open source driver?
What does "RISC-V" is royalty free mean? Does that make an RPi more expensive because they have to pay ARM?
What do the H.265/H.264 encoder/decoders do? Is that important when connecting a USB camera (converting from whatever the camera provides to H.265/H.264)? And then is it the same thing, i.e. that an RPi is more expensive because it has to pay to use H.265/H.264?
More than the royalties, shouldn't we care about binary blobs? The more open the hardware is, the easier it is for the community to maintain it, right?
The RISC-V foundation published the specs for RISC-V and the extensions. These are available royalty-free and can be implemented by anyone. There are various chip designers that create RISC-V compatible CPU cores, and you would pay one of these companies to incorporate that design onto your own chip. Or you could adapt one of the open-source CPU designs, but those are not very high-performance. Or you could design your own, like Western Digital has.
For an ARM design, you pay a license fee to ARM Ltd, even if you design your own core.
So what really matters is how much you are paying to license the CPU core, if you don't design it yourself.
> More than the royalties, shouldn't we care about binary blobs? The more open the hardware is, the easier it is for the community to maintain it, right?
Yes, but the chip vendor needs to publish full documentation for the hardware too. Without that, it is harder to write your own device driver software.
No NVME port.
Price tag is too high.
Shame because the rest of the H/W looks nice.
Then I return to the ordinary Intel world where stuff works.
Why is this not a TI SoC?
It's why they called it the BeagleV ;)
I've been quite happy with the documentation for the AM335x processors on the standard, ARM-based Beaglebone Black.
But the readme at [1] is exactly why I'm reluctant to pick this board:
> Tracking mainline u-boot/kernel with T-Head patches as needed
> Additional SoC details (Chinese language is good) - pointers to licensed IP is fine
> Clear legal path to usage:
>> Verify the IP in the SoC is licensed for use
>> Verify the IP user documentation can be public [emphasis original, why not the developer documentation?]
>> Signed 3P agreement
> SDK source required to test board
> Documentation needs to launch:
>> Additional SoC details (Chinese language is good) - pointers to licensed IP is fine
You'll pay more for an NXP, TI, or ST-branded SOC than for an Allwinner, Rockchip, or "T-head" one, but even if all you're paying for is documentation it's well worth it IMO.
Edit: It's great that the processor core is an "XuanTie C910 open-source RTL RISC-V". Open-source RTL, wow! The Verilog is up on GitHub [2]! You'll never get that from TI! But the processor core is only a small part of the SOC, there's a ton of other peripherals and other closed-source, closed-documentation IP to run them.
[1]: https://git.beagleboard.org/beaglev-ahead/beaglev-ahead/-/bl...
[2]: https://github.com/T-head-Semi/openc910/blob/main/C910_RTL_F...
50GFLOPS, 3Mpixel/s Imagination BXM-4-64 graphics processing unit (GPU)
Has got to be a typo? 3 million pixels per second is not very impressive, to understate things a bit.
Edit: also, in Sweden Digi-Key want almost $180 for this which was more than I expected. Wow.
In fairness, the Cortex-A72 in the Raspberry Pi is the nth iteration of Arm cores whereas the C910 is essentially the 1st generation (the C906 is completely different and in-order). I wouldn't make too many conclusions based on this about the future of RISC-V and its implementations, but I'm looking forward to the next wave of higher performing cores coming to market.
You might not have the optimal settings.
It's also possible that the TH1520 doesn't have enough cache for SPECint.
In my own testing building riscv-gnu-toolchain on both I've found the SG2042 EVB with -j4 to be 1.55x the speed of the LicheePi4A. The SG2042 had the same C910 cores but a lot of L2 and L3 cache (and 64 cores, but I limited it to 4 of them for this test).
Scaling your 7.64 SPECint by 1.55x gives 11.8, so that's the same ballpark.
My VisionFive 2 does the same build 1.13x faster than the LiCheePi4A. That's using the same src&build trees on the same Samsung 2 TB USB3 external SSD.
The TH1520 has 64k L1 icache and 64k L1 dcache, plus 1 MB shared L2 cache.
The JH7110 in the VF2 has only 32k each L1 icache and dcache, but 2 MB shared L2 cache.
The SG2042 has 64k each L1 icache and dcache, 1 MB shared L2 cache per 4 cores (so far, the same as TH1520), 4 MB of local L3 cache per 4 core cluster, and 60 MB of L3 cache on the other 15 clusters that is also usable at about 2/3 the bandwidth (twice faster than RAM).
The Pi4 also seems to have only 1 MB L2 cache. Which makes me wonder ... was your code compiled 32 bit or 64 bit?
ADD: it's unlikely the amount of cache and more likely their quite long L2 hit latency which is a lot longer (in wall-time) than, say a Cortex-A72.
For that matter, the 20% difference you found could be compiler maturity. And it's small enough that it's hard to notice without sitting two machines doing the same thing next to each other, or using a stopwatch.
But yeah, could well be that TH1520 has a duff L2 cache design in some way.
Much more shocking to me than the Pi 4 beating the TH1520 by 20% is the in-order dual-issue, 20% slower clock speed JH7110 beating it by 13% on a GNU toolchain build.
On my primes benchmark it comes in (at 1.848 GHz) at 10.43 seconds vs 12.1 for a Pi 4 running A64 code.
The other common RISC-V SoC right now, the JH7110, which is on quite a bit cheaper boards such as the VisionFive 2 and Pine64 Star64 and Milk-V Mars, comes in at 14.9 seconds. That's more or less an A55 equivalent.
I submit that it is no worse than Dhrystone or Coremark, and correlates well with those while being a lot less code. It is better than those at being impervious to tricky compiler or library optimisations -- I have seen for example libc string function implementations that unroll a loop processing 32 bit words 5 times, not 4 or 8. Why? Well, Dhrystone just happens to call that function with an 18 byte string. Every time. Ugh.
They all exercise just the CPU core (load/store, arithmetic, branching) and L1 caches or SRAM. Which is not a full-system test, but is valuable information.