The best performance this year will be SiFive's "HiFive Unmatched" with four cores more or less equivalent to an ARM A55. Raw speed should be a little quicker than a Raspberry Pi 3, but the user experience will be better because it has an M.2 slot for a modern SSD, a PCIe slot that Radeon graphics cards work in (they demonstrate it with an RX 580), and 16 GB RAM. Pricey at $665 for the Mini-ITX motherboard with CPU and RAM, but it will give the best user experience. Production version is due to ship at the end of this month.
Next is the BeagleV "StarLight". It uses the same SiFive cpu cores but in an SoC from a different company, and with a built in PowerVR GPU. It runs off SD card, but once booted can use USB3 disks. At $119 for 4 GB or $149 for 8 GB it's not a lot worse of a computer than the Unmatched. Due to ship September, I have a beta developer board now.
Allwinner have their D1 chip in mass production right now. It has a single core running at 1.0 GHz with a draft version 0.7.1 128 bit RISC-V Vector unit, which improves the speed often 2-3x. Sipeed and Pine64 have promised Linux boards using the chip in the next couple of months starting at $10 or $12. Probably with only 256 MB or 512 MB RAM at that price. That's very competitive against Raspberry Pi Zero. I've had access to an Allwinner Evaluation Board for a couple of weeks and it's very very nice is they can get boards out at those prices.
All the above are 64 bit and run Fedora, Debian, Ubuntu (I recommend Ubuntu as they have 21.04 images for RISC-V) and others coming.
If you want a full featured desktop experience with web browser loading heavy sites, watching YouTube etc then you'll want the Unmatched, but the BeagleV will be close. Note: such a web browser isn't available yet, but once developers have these boards themselves as daily drivers it will happen.
While the Unmatched / BeagleV CPU is similar to a Pi 3, with more RAM and better peripherals (especially in the Unmatched) I expect the overall experience to be like a Core 2 Duo from the mid 2000s, maybe better for many things with a decent video card. Think: original MacBook Air.
Wow, getting Haiku on a board like that with proper "tight" hardware driver support would be so cool! Makes me think of the original BeBox and how much I wanted one. It, too, was dual-core! :)
Boards at that price level will have to wait until after the component shortage, but I believe it may be possible to order a higher spec'd D1 board for under $100 within the next few days and receive it possibly before the end of the month.
