81–90 of 166 posts
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While the ref clock is only 100MHz the data rate of PCI Express is much higher, it's a serial bus pushing multiple gigabits a second https://electronics.stackexchange.com/a/259002
Yes, the theoretical maximum (nyquist freq) of PCIe 4 is 8ghz
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If I’m reading it right, don’t you give up USB to get this PCIe access?
Bet the broadcom SoC has a USB controller built in, but unused... You could hook it up?
That's really cool. I'm curious, would it be possible to use a modern GPU (running at 1x) on an ARM based board? Would the open source drivers that are part of the Kernel work out the box on ARM?
Hack’s creator here - it’s on my list of things to try. GPUs are notoriously hard to get to work on non-intel, having tried to get a few up on Alpha and Itaniums in the past. VideoBIOS expects to run and expects a well behaving Intel CPU to do the power-up. That said X can sometimes emulate these quite well. On ARM we’d also run into alignment issues and likely other quirks - but in principle...
the form factor of pcie devices doesn't really play well with rpi, but there's definitely a need for faster, more stable persistent storage. i have heard a lot of issues with microsd cards based on wear leveling and such. it would be really nice if rpi could develop like an m2 interconnect where i could install an nvme ssd within the form factor of an rpi, that would make for a truly incredible little machine.
It looks like an unreliable modification. Running a GHz-level interface with jumpers is almost impossible to control the impedance, it's a cool Proof-of-Concept though. But is it possible to bring the project to the next level? Is it possible to make a daughterboard with QFN connector? If so, one can make a pin-compatible daughterboard with an extension connector. To use it, just desolder the USB chip and solder a ne…
It looks like an unreliable modification. Running a GHz-level interface with jumpers is almost impossible to control the impedance, it's a cool Proof-of-Concept though. But is it possible to bring the project to the next level? Is it possible to make a daughterboard with QFN connector? If so, one can make a pin-compatible daughterboard with an extension connector. To use it, just desolder the USB chip and solder a ne…
36 gauge wire, and twisting them into pairs would help, or parallel and flat against the PCB.
Hijacking the thread: I develop remotely on VPSes because I like to have an always-on box reachable from any client. I am wondering if a RP4 offers a similar experience at lower cost. Does anyone use a RP for this?
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I always wondered what the deal was with Video BIOS on modern PCI-express graphics cards. Obviously it must exist, since int 10h still works. Does video BIOS even need to be executed, though? I always assumed it was only necessary for the primary card to be able to display output during boot on PCs . (Otherwise, wouldn't two different cards trample over eachother's implementation of int 10h?) Sorry for the probably-o…
It’s all, cough, implementation dependent. You can run two VideoBIOS implementations, and chances are only one will install an int10h handler, but both will set up the registers and whatnot in the GPUs. My AMD TAHITIs for instance need VideoBIOS to start some form of thermal management loop - otherwise they just run full-throttle on the fan. Then whichever card prevails (BIOS has the ability to select the initializat…
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Thanks for the information. I’ve been really curious about this with the incoming ARM dev boards that have full PCI-e edge connectors. Pretty fascinating that X11 of all things is dealing with Video BIOS initialization, though. The sheer amount of functionality that was overloaded into X...
You don't need X, and I wouldn't assume its remnants of userspace mode setting would work on non-x86. The amdgpu kernel driver POSTs the GPUs when loaded just fine! I run an RX 480 on a MACCHIATObin with FreeBSD and Wayland only :) Plus, there are two ways to get the GPU in UEFI already – X86EmulatorPkg and native aarch64 GOP driver builds provided by AMD.
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Yes, the theoretical maximum (nyquist freq) of PCIe 4 is 8ghz
The Pi4 isn't PCIe Gen 4, though. It's only PCIe Gen 2. Max speed of PCIe Gen 2 is 5GT/s, which equates to the same speed as standard USB3.0/USB3.1 Gen1/whatever its called nowadays.