4 ms·
This: > If you want to do any OS work, you need a system that implements the Privileged ISA. Supporting the Privileged ISA is synonymous to being able to run
by Quequau 7y ago
This:
> If you want to do any OS work, you need a system that implements the Privileged ISA. Supporting the Privileged ISA is synonymous to being able to run UNIX-like systems, because it brings user-/supervisor-mode distinction and paging. Working on real hardware is generally preferred to working in emulators, because the code eventually has to run on metal anyway and emulators can be too forgiving for certain classes of problems. There is a plethora of RISC-V microcontrollers for a couple of dollars that all don’t support the Privileged ISA. At the time of writing, the only board you can buy that does support it is the $1000 HiFive Unleased, which was beyond my “I just want to play around with this” budget.
Suggests to me that it's at least part of why Stephen Marz [0] isn't trying to target a specific board with his project (which has been posted here a few times and I'm sorta following along). That pretty much kills most of the interest in RISC-V that I had in me.
I guess I'll wait a few more years and check back again later.
[0]: https://osblog.stephenmarz.com/index.html https://osblog.stephenmarz.com/index.html
- pjc50 7y agoFor some reason, people have a fantasy that RISC-V is going to give them a sub-dollar microcontroller that runs Linux, rather than being like ARM where "microcontroller" and "Linux capable" and "server grade" are three entirely different market segments.
- rjsw 7y agoI have several ARM dev boards and am thinking of getting a PinePhone, am happy to pay upto $200 for something to play with but not $1000. The HiFive Unleashed is interesting in that it has a lot more RAM than cheap ARM dev boards, for the same money though I could get a HoneyComb LX2K ARM system.
- floatboth 7y agoNot for the same money, for much cheaper. HiFive Unleashed is $1000 for the board with onboard RAM… but it does not have PCIe onboard, so if you want that, you could pay $2000 extra (!!) for the "HiFive Unleashed Expansion Board" that has a giant FPGA that has a PCIe root complex programmed on it. HoneyComb LX2K is $750 for the board with 64GB eMMC + bring your own SODIMMs for RAM. SolidRun also offers the MACCHIATObin for $339. 4-core A72 + 4GB full-size DIMM included. (The single-channel-ness of the RAM is not good for performance, but you can install a big 16GB DIMM no problem.) Both the LX2K and the mcbin have PCIe of course :)
- Quequau 7y agoI've never met anyone who believed that RISC-V was going to give them a sub-dollar microcontroller that ran Linux before. That seems like a fairly unreasonable expectation, given today's market and RISC-V's position in it.
- warrenm 7y agoI've met folks like that - ones who're getting ready to bet the farm on RISC-V taking-over not merely IoT, but mobile devices (phones, tablets, watches, wearables)
- rwmj 7y agoAre there sub-dollar ARM microcontrollers that run Linux? Anyway there are a bunch of cheap (not sub-dollar, but sub $30) RISC-V chips coming out of China this year which will run Linux.
- pjc50 7y agoNot quite, but the "Linux business card" that went round recently uses the F1C100s, which is $3.50 including RAM in package. https://www.thirtythreeforty.net/posts/2019/12/my-business-card-runs-linux/ https://www.thirtythreeforty.net/posts/2019/12/my-business-c...
- alasarmas 7y agoAccording to this link, the F1C100s has 32 Mbytes (!) of DRAM, which is pretty amazing for $1.42 USD in small quantities: https://www.cnx-software.com/2018/08/17/licheepi-nano-cheap-sd-card-sized-linux-board/ https://www.cnx-software.com/2018/08/17/licheepi-nano-cheap-...
- almindor 7y agoThis is untrue. Hifive1 supports the privileged instructuons and comes with machine mode and user mode. Cost is ~50$
- zozbot234 7y agoLinux and other UNIX-like systems (with virtual address space and the like) need Supervisor mode (S-mode), not just U+M mode.