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ULX3S: Hackable FPGA that runs Linux on RISC-V

ulx3s.github.io

71–80 of 85 posts

Re: ULX3S: Hackable FPGA that runs Linux on RISC-V

#73
post #60

Earlier quoted context omitted.

Oh wow, I had no idea they were that advanced. How much do these go for secondhand?

There is no sensible secondhand market for things like this; it will be embedded in someone's board. And there aren't many about to start with. Sometimes people are lucky enough to find decent FPGAs in scrap, but it's like panning for gold.

I've recently bought second-hand Xilinx FPGAs on Ebay for $250 each with list price of $3500. They come on boards that have an unidentified manufacturing fault. Salvaging and reusing the chips seems realistic using a budget vapor phase soldering setup (not attempted yet) but the challenge for me is designing or otherwise acquiring suitable PCBs to put them onto. I'm told that you can potentially find suitable PCBs on Aliexpress but I haven't looked into this in detail yet.

In other words, there doesn't seem to be much demand in the secondhand market, and you can potentially use that in your favor to take advantage of supply selling at steep discounts.

Re: ULX3S: Hackable FPGA that runs Linux on RISC-V

#75
post #3

Also newsworthy: Lattice drops recent EULA clause forbidding fpga bitstream reverse engineering https://hackaday.com/2020/06/06/lattice-drops-eula-clause-fo... therefore 2020 could be a milestone for open FPGA toolchains!

I initially misunderstood this headline to mean the opposite: I took "drops" to mean "introduces", which is the opposite of the intended meaning -- "withdraws". Not sure where I got this non-mainstream meaning of "to drop".

It's what most hip clothing brands do to launch merch. Look at Supreme as an early example. Artificially limited stock, released like Black Friday. Scarcity ups the coolness and bragging factor. It's somewhat odd though many times - take Supreme example - the retail costs don't actually match the demand (they could charge higher) not supply side and a large re-sale market opens (even stockx.com a real market with order book)

Re: ULX3S: Hackable FPGA that runs Linux on RISC-V

#76
post #69
post #67

Earlier quoted context omitted.

Why would they change an EULA clause for that?

To signal potential open source contributors that there is no danger of being sued for their work. Too many vendors have used the fact or even just the accusation of reverse-engineering or other non-EULA-compliant behaviour to suppress OSS.

That's a valid reason. But not what I asked.

I don't see a connection to "outsource tool development to some other company".

If I commission some work from another company, this company doesn't receive, modify or extend my software under the standard EULA. They do so under our contract.

Re: ULX3S: Hackable FPGA that runs Linux on RISC-V

#77
post #7

2x more resources compared to $30 https://github.com/q3k/chubby75 at 5x the price

I handle most of pull requests and issue tracking on the chubby75 project: it's a great FPGA board for experimenting, but only if you need to drive a lot of IOs and don't have any GPIO input requirements.

A replacement for the general purpose ULX3S it is not.

Re: ULX3S: Hackable FPGA that runs Linux on RISC-V

#78

Is there any published rationale for the RISC-V instruction encoding? A few months back I set out to write a software emulator of RISC-V for fun. I expected the instruction set encoding to lend itself well to a very simple implementation, eg. something you could decode in 5-10 lines of C plus some tables. But the instruction encoding is much more irregular than I expected: https://github.com/ucb-bar/riscv-sodor/blob/…

I spent some time defining an alternate encoding of the base instruction set. I dont think they did a good job, but it's also not easy to do better. I started from an assumption of variable length - 16 bit or 32 bit opcodes plus immediate data in 16 bit chunks. It's not easy. Remember all those strange bit positions are irrelevant in hardware. But they are a bitch for things like linkers.

>Remember all those strange bit positions are irrelevant in hardware.

What, they are absolutely relevant in hardware and selected to optimize the resulting generated hardware.

Re: ULX3S: Hackable FPGA that runs Linux on RISC-V

#79
post #76
post #69

Earlier quoted context omitted.

To signal potential open source contributors that there is no danger of being sued for their work. Too many vendors have used the fact or even just the accusation of reverse-engineering or other non-EULA-compliant behaviour to suppress OSS.

That's a valid reason. But not what I asked. I don't see a connection to "outsource tool development to some other company". If I commission some work from another company, this company doesn't receive, modify or extend my software under the standard EULA. They do so under our contract.

The idea was that some outside company had a say in what went into the EULA.

Re: ULX3S: Hackable FPGA that runs Linux on RISC-V

#80
post #7

2x more resources compared to $30 https://github.com/q3k/chubby75 at 5x the price

I handle most of pull requests and issue tracking on the chubby75 project: it's a great FPGA board for experimenting, but only if you need to drive a lot of IOs and don't have any GPIO input requirements. A replacement for the general purpose ULX3S it is not.

Is this because people using it cant solder and replacing SOP24 package with 8 jumpers is a show stopper?
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