+1000 points for the PiKVM V4 Plus. We (Revise Robotics - a YC company!) refurbish laptops with robots and AI - as part of this, we (or rather, the AI) send(s) keyboard commands in software to the computers we're refurbishing.
How/why? The AI needs to navigate the BIOS among other tasks - so we need a KVM to send arrow down and enter, roughly speaking.
We were a GL.iNet KVM shop until we ran into a nasty issue with a specific ThinkPad - the GL.iNet would send an incorrect USB 0 byte which most laptops ignored, except this ThinkPad which was freaked out by it / beeped / wouldn't accept any key command.
I couldn't let this problem go, so I got a low level USB debugger [0] (which I extremely recommend) and wire-debugged the USB signal, A/B comparing the GL.iNet and the PiKVM. The PiKVM was doing things properly (usb-wise), so we swapped all (~10) of our KVMs for it.
I also remember that the GL.iNet was stranger/more difficult to customize (it's just running pikvm the software but doesn't let you customize it as much). The GL offers a nicer UI, but it doesn't matter that much (we drive it via API) and we're happy to support the actual PiKVM authors/company. It's a fantastic product. Not cheap, but truly truly great.
P.S. If someone from GL wants to reach out, I can offer you a lot of low-level debugging info -- fixing this issue would be great.
Okay, there were two things that bothered me with these KVM switches: the power adapters are massive so there's too many cables, and the cables don't go always in the same side of the thing. Your post covers both and I'm thrilled. The final thing I recognize is a bit of a nice to have but the only thing that I want to rack that doesn't have a BMC is my Mac Mini which I've hesitated to put in the Sonnet RackMac and run because I don't know how to KVM power it on/off. My cabinet is an hour away from me and the Mac Mini runs the family AI agent so I need it to be available all the time. So far, it hasn't ever needed any attention (it comes back on after power outages at home) but I'd prefer to be able to turn it on/off remotely ideally.
Do you know which one of these works well with that?
Not affiliated but I had good experience with GL.inet’s comet line [1]. They have one on kickstarter that’s the size of a google cast puck that uses purely usb-C. Though all my KVM do not have internet access (blocked at my gateway). I can only access it via tailscale externally.
Hey Jeff, I did some research on the jetkvm after reading this as I was very impressed but wanted full scale hdmi + Poe and was going to pull the trigger on the clone you mentioned later, ArkKVM but felt like I’d rather support the main project if I could…
What I found seems to indicate that Jet fixed those two issues in a hardware revision but it’s really difficult to distinguish the new on from the old as they’ve seemingly kept the same name and not added a v2 or something like that to the naming. One of their vendors has a Poe va non poe sku, the other has a an emmc vs tf card sku. All seemingly without a name distinguishing them.
There’s also just chaos on Amazon as they are being sold in at least 4 separate listings with no name distinguishing which model is which, non of them mention poe and all claim full size hdmi.
In any case I thought you should know that your write up is out of date here but you probably need to do some digging to figure it out.
It will never make sense to me why KVMs are such a hard problem to solve. It seems like something we should have a good answer for by now but we still really just don't without dropping hundreds of dollars, and even then it still feels like a crap shoot.
It’s bizarre that one needs to do all this via a keyboard/monitor interface.
Nearly thirty years ago when I used to work on Silicon Graphics kit everything from powering on and off a server to installing the OS from scratch over the network could be done out of band via serial - and automatically, using expect(1)
They aren't a hard problem to solve. In the server market it's completely solved with a BMC. The problem being solved here is someone wants to make a product using some commodity product like a raspberry pi, perform video capture on a VGA/HMDI/DP port. This is not actually a problem end users have.
If you want to plug into a system that isn't server class, then they should be producing a video card that hooks into the USB bus, the always on rail of the power supply, the power switch pin of the power supply, and has an RJ45 jack. The contents of the card should be an off the shelf BMC chip.
But realistically if you want this kind of functionality, just buy server class systems that come with it.
I have a CSE847 and HP DL380 G10 that have gone down for me due to power outages. Many of these look complex, and I basically just need remote power-on/toggle capability. Should I be looking at something else?
You could configure BIOS/UEFI to power-on when power is restored (or return to last state). Or use wake-on-LAN, which quite a few consumer routers can send through their web interface.
Don't your servers already have BMCs supporting IPMI to provide full remote management? Often features like full KVM will require extra licensing, but remote power on is one of the most basic features and I've never encountered a BMC that didn't provide at least that much remote control.
Sounds like you might need a UPS/Battery backup for outages.
Some of those servers can have multiple power supplies for failover too. They also can have cards in them to power them on/off remotely as well as long as they have power.
I have a mild distrust of some of the cheap IP KVMs. I don't think vendors are malicious, but I don't expect they get it right every time either.
Admittedly, I haven't looked at any open-sourced firmwares either which could have improved things.
I have found the Sispeed USB KVM very useful, the convenience is well worth the $50 it cost me. The UX isn't great but you don't really need it to be. It works (most of the time) via WebUSB for the keyboard mouse.
I went with Sipeed NanoKVMs across my homelab as well and I've also been happy with them. For a while it's been the best value option cf. GL.iNet, PiKVM, and JetKVM. The PoE versions are great in a rack and the integrated ATX control is fully-featured (including the little power switch icon in the web UI turning green when the system is powered on). I set up an isolated OoBM VLAN with no Internet access and any switch ports assigned to it are isolated by default as well.
Always a fun adventure when you buy an old server motherboard to see what state of disarray the BMC is in. Or if you have to patch the license on older boards just to get into it. Usually I just ignore the BMC on any hardware more than 5 years old.
How's the video quality/latency on all of these? RDP or parsec are probably the gold standard, but I doubt cheap arm SOCs can implement either properly.
On some the latency is within 45-60ms (that's the best I've tested, under pretty strict LAN conditions), but average is more like 100-200ms. Not good enough for gaming, but fine for things like watching video, if you really want to do that.
Most employ heavy compression by default, and it looks a little more pronounced with motion. A few have 'high quality' mode, but especially on the Pi-based KVMs this eats up more CPU, so I don't use that.
It's on the whole best for use cases where you just need to log into remote servers and check on things, or reinstall/re-image something. I don't think I'd like using any of these for a constant remote session for daily work. I do use Screen Sharing on macOS for that sometimes, and it works great in its low-latency mode. None of the KVMs I've tested are quite to that level.
I'm running a PiKVM DIY on a pi02w. Adequate, but I'd like more functionality and performance.
I bought a SiPeed NanoKVM. It caught fire 15 minutes after being plugged in. Despite providing pictures of the charred PCB, they insisted I ship it back, costing me €20, and then tried 3 times during the transit to get AliExpress to void my return as fraudulent. I eventually provided proof of signed delivery to their people on the last possible day of my final appeal, and AliExpress ruled in my favor, refunding my purchase price but not the return shipping cost. Better some money back than none at all!
Another vote for JetKVM. Tailscale support is great. I'm glad to see audio is in the works because a Mac mini screaming from separate room during a remote session is disappointing.
+1000 points for the PiKVM V4 Plus. We (Revise Robotics - a YC company!) refurbish laptops with robots and AI - as part of this, we (or rather, the AI) send(s) keyboard commands in software to the computers we're refurbishing.
How/why? The AI needs to navigate the BIOS among other tasks - so we need a KVM to send arrow down and enter, roughly speaking.
We were a GL.iNet KVM shop until we ran into a nasty issue with a specific ThinkPad - the GL.iNet would send an incorrect USB 0 byte which most laptops ignored, except this ThinkPad which was freaked out by it / beeped / wouldn't accept any key command.
I couldn't let this problem go, so I got a low level USB debugger [0] (which I extremely recommend) and wire-debugged the USB signal, A/B comparing the GL.iNet and the PiKVM. The PiKVM was doing things properly (usb-wise), so we swapped all (~10) of our KVMs for it.
I also remember that the GL.iNet was stranger/more difficult to customize (it's just running pikvm the software but doesn't let you customize it as much). The GL offers a nicer UI, but it doesn't matter that much (we drive it via API) and we're happy to support the actual PiKVM authors/company. It's a fantastic product. Not cheap, but truly truly great.
P.S. If someone from GL wants to reach out, I can offer you a lot of low-level debugging info -- fixing this issue would be great.
[0] https://greatscottgadgets.com/cynthion/
Okay, there were two things that bothered me with these KVM switches: the power adapters are massive so there's too many cables, and the cables don't go always in the same side of the thing. Your post covers both and I'm thrilled. The final thing I recognize is a bit of a nice to have but the only thing that I want to rack that doesn't have a BMC is my Mac Mini which I've hesitated to put in the Sonnet RackMac and run because I don't know how to KVM power it on/off. My cabinet is an hour away from me and the Mac Mini runs the family AI agent so I need it to be available all the time. So far, it hasn't ever needed any attention (it comes back on after power outages at home) but I'd prefer to be able to turn it on/off remotely ideally.
Do you know which one of these works well with that?
Not affiliated but I had good experience with GL.inet’s comet line [1]. They have one on kickstarter that’s the size of a google cast puck that uses purely usb-C. Though all my KVM do not have internet access (blocked at my gateway). I can only access it via tailscale externally.
[1] https://www.gl-inet.com/products/gl-rm1/
Hey Jeff, I did some research on the jetkvm after reading this as I was very impressed but wanted full scale hdmi + Poe and was going to pull the trigger on the clone you mentioned later, ArkKVM but felt like I’d rather support the main project if I could…
What I found seems to indicate that Jet fixed those two issues in a hardware revision but it’s really difficult to distinguish the new on from the old as they’ve seemingly kept the same name and not added a v2 or something like that to the naming. One of their vendors has a Poe va non poe sku, the other has a an emmc vs tf card sku. All seemingly without a name distinguishing them.
There’s also just chaos on Amazon as they are being sold in at least 4 separate listings with no name distinguishing which model is which, non of them mention poe and all claim full size hdmi.
In any case I thought you should know that your write up is out of date here but you probably need to do some digging to figure it out.
It will never make sense to me why KVMs are such a hard problem to solve. It seems like something we should have a good answer for by now but we still really just don't without dropping hundreds of dollars, and even then it still feels like a crap shoot.
It’s bizarre that one needs to do all this via a keyboard/monitor interface.
Nearly thirty years ago when I used to work on Silicon Graphics kit everything from powering on and off a server to installing the OS from scratch over the network could be done out of band via serial - and automatically, using expect(1)
That’s progress, I guess.
They aren't a hard problem to solve. In the server market it's completely solved with a BMC. The problem being solved here is someone wants to make a product using some commodity product like a raspberry pi, perform video capture on a VGA/HMDI/DP port. This is not actually a problem end users have.
If you want to plug into a system that isn't server class, then they should be producing a video card that hooks into the USB bus, the always on rail of the power supply, the power switch pin of the power supply, and has an RJ45 jack. The contents of the card should be an off the shelf BMC chip.
But realistically if you want this kind of functionality, just buy server class systems that come with it.
Neat, someone mentioned these when I proposed a ludicrous anti-fingerprinting strategy https://news.ycombinator.com/item?id=44549352
Jeff Geerling rocks
I have a CSE847 and HP DL380 G10 that have gone down for me due to power outages. Many of these look complex, and I basically just need remote power-on/toggle capability. Should I be looking at something else?
You could configure BIOS/UEFI to power-on when power is restored (or return to last state). Or use wake-on-LAN, which quite a few consumer routers can send through their web interface.
Don't your servers already have BMCs supporting IPMI to provide full remote management? Often features like full KVM will require extra licensing, but remote power on is one of the most basic features and I've never encountered a BMC that didn't provide at least that much remote control.
Sounds like you might need a UPS/Battery backup for outages.
Some of those servers can have multiple power supplies for failover too. They also can have cards in them to power them on/off remotely as well as long as they have power.
Glad I bought a JetKVM, it's been great (other than the HDMI adapter, lol)
I have a mild distrust of some of the cheap IP KVMs. I don't think vendors are malicious, but I don't expect they get it right every time either.
Admittedly, I haven't looked at any open-sourced firmwares either which could have improved things.
I have found the Sispeed USB KVM very useful, the convenience is well worth the $50 it cost me. The UX isn't great but you don't really need it to be. It works (most of the time) via WebUSB for the keyboard mouse.
I went with Sipeed NanoKVMs across my homelab as well and I've also been happy with them. For a while it's been the best value option cf. GL.iNet, PiKVM, and JetKVM. The PoE versions are great in a rack and the integrated ATX control is fully-featured (including the little power switch icon in the web UI turning green when the system is powered on). I set up an isolated OoBM VLAN with no Internet access and any switch ports assigned to it are isolated by default as well.
Part of the problem is the absolute crap that most vendors throw on an AST2600 is even worse.
I will say iDRAC has been a lot more reliable for me, but the chance I'll ever buy a Dell server for home use is basically 0.
Always a fun adventure when you buy an old server motherboard to see what state of disarray the BMC is in. Or if you have to patch the license on older boards just to get into it. Usually I just ignore the BMC on any hardware more than 5 years old.
Have you played around with OpenBMC or any of the open-sourced BMC firmware alternatives?
Radxa also released their ipkvm product last week called radxa linkr. It costs by $55
I deploy pikvm and I have been mostly happy. The tinypilot has a better feel to it. Something feels more polished.
How's the video quality/latency on all of these? RDP or parsec are probably the gold standard, but I doubt cheap arm SOCs can implement either properly.
On some the latency is within 45-60ms (that's the best I've tested, under pretty strict LAN conditions), but average is more like 100-200ms. Not good enough for gaming, but fine for things like watching video, if you really want to do that.
Most employ heavy compression by default, and it looks a little more pronounced with motion. A few have 'high quality' mode, but especially on the Pi-based KVMs this eats up more CPU, so I don't use that.
It's on the whole best for use cases where you just need to log into remote servers and check on things, or reinstall/re-image something. I don't think I'd like using any of these for a constant remote session for daily work. I do use Screen Sharing on macOS for that sometimes, and it works great in its low-latency mode. None of the KVMs I've tested are quite to that level.
I'm running a PiKVM DIY on a pi02w. Adequate, but I'd like more functionality and performance.
I bought a SiPeed NanoKVM. It caught fire 15 minutes after being plugged in. Despite providing pictures of the charred PCB, they insisted I ship it back, costing me €20, and then tried 3 times during the transit to get AliExpress to void my return as fraudulent. I eventually provided proof of signed delivery to their people on the last possible day of my final appeal, and AliExpress ruled in my favor, refunding my purchase price but not the return shipping cost. Better some money back than none at all!
Maybe just buy the JetKVM. It looks nice!
Another vote for JetKVM. Tailscale support is great. I'm glad to see audio is in the works because a Mac mini screaming from separate room during a remote session is disappointing.