MPU4032 IP KVM Questions: Connection for RS-232 Serial Devices? Fan Replacement? HDMI?

[Rand__]

I you dont throw it around too much tape should be ok.
O/c the heat might reduce the adhesiveness of the tape over time, but for a while that should be fine

 

[John T Davis]

I you dont throw it around too much tape should be ok.
O/c the heat might reduce the adhesiveness of the tape over time, but for a while that should be fine

Thanks.

Kapton tape is supposed to be heat resistant for long term use, but then again this is fake/clone Kapton tape, so … YOLO time.

 

[John T Davis]

Fan mod complete.

I used (single side) VHB A/V mounting tape to hold the fans in place. They're quite well stuck, and VHB seems to only get stronger over time even when heated. The 40 mm fans are only just short enough to fit in the 1U chassis; another milimeter and they wouldn't have worked. So I've got a pressure/friction fit from the top case, as well.

EDIT @ Wednesday, August 27, 2025: I also ended up putting (again, only single side adhesive) VHB tape on the tops of the fans. It squishes enough that it doesn't interfere with putting the case on, and helped absorb and stop a lot of the vibration noise--3 40mm Noctua 3-pins move quite a bit of air.

The Noctua fan cables are stupidly long, so I've got quite a bit of taped up, folded up fan wires floating around in there that probably make a bit of noise from time to time when the fans ramp up, but that's fine. As long as the wires stay out of the fan blades.

Of course, right now I can't actually figure out how to expose the internal temperature or fan data; hopefully once I have SSH access with an actual admin account, more data will be exposed.

3x 40mm Noctuas move quite a bit of air. Probably not as much as the bespoke 3x30mm setup, but it's blowing cold air out the exaust, so I'm feeling pretty good.

Thanks for the help, everyone.

But I think it worked.

 

[John T Davis]

I'm back.

It works, though I'm really struggling with video quality/scaling issues on the devices I have connected.

At the moment, I don't really consider it usable for the purpose I bought it for. I can't even read a full line of console text without something getting cut off on both sides.

Lots of noise, and no matter what I set the the KVM settings for resolution, I'm getting 4:3 640x480 video out both in the HTML 5 viewer and with a video scaler that has a VGA input (the video scaler is smart enough to tell me the resolution of the incoming signal, which tipped me off that it's stuck in 640x480).

That's not ideal--the modern linux servers I'm connecting to for TTY console sessions apparently can't deal with 640x480 at all. Most of the left and right of the screen is cut off. It's showing some sort of widescreen signal.

I think I can set up a custom display profile in Linux for TTY sessions to force a certain resolution (somehow; I haven't had to correct a TTY/console output resolution in 10 years), but that would just be treating a symptom. A brief trip to the ArchWiki tells me I'll need to learn about setting framebuffer parameters. Neat.

The system is picking up the MPU as a 22" monitor with supported resolutions of 720x480 or 640x480. Here's what inxi has to say about it. (Sorry for the terrible image; the text is so noisy it was moving like ants.)


The 1920x1080 resolution corresponds to the "Hardware Presented" setting in the KVM. I set it to 1080p.

This doesn't make any sense to me; in the KVM Session settings, the "Standard" (default) presented monitor resolution is 1024x768 ... which is still bigger than the 480p "max" shown in inxi.

EDIT: I'm using the Avocent MPUIQ-VMC (not the newer VMCHS) modules. The MPU4032 reports that they're running the latest firmware and Upgrade Status is "Ready."



@Rand__ @gregsachs , any recommendations for HDMI to VGA converters that won't mangle the HDMI signal and force downscale it? What do y'all use?

EDIT 2:
(That said, it seems like the issue is how the MPU is reporting it's capabilities in Linux…
I wonder if I need to install a driver for this thing.

I just had a hunch and checkeed the manual.


Input Video Resolution seems to be the key.
If I had to guess, the Linux TTY/fbdev are locking on to the 640x480 60 Hz mode and not trying to go bigger. The presence of 75 Hz modes might actually be confusing Linux, too.

And those widescreen modes are unusual … until you realize they're 16:10 aspect ratio.
No way is the TTY gonna autoconfig that correctly.

So, I need to figure out how to mode set to one of the wide-screen ones to work with my wide screen displays. I think. A project for the weekend, probably.

Welcome all my friends, the tinkering never ends…

 

[Rand__]

Sorry, i never used HDMI, maybe a DP port but most of the time only VGA...

 

[gregsachs]

I'm in the same position, have used a DP adapter but never HDMI.
Do you have a monitor hooked up to the local console? I"m not sure if that impacts or not...

 

[John T Davis]

I'm in the same position, have used a DP adapter but never HDMI.
Do you have a monitor hooked up to the local console? I"m not sure if that impacts or not...

@gregsachs @Rand__ :

Thanks for your replies. I ran a VGA cable from the KVM itself to a VGA input on a video scaler/input switcher I use (4 HDMI, 2 VGA, DVI, Composite) that's hooked up to a portable 1080p HDMI monitor. I have one monitor and several devices (mostly HDMI) that need to output video, so this has been a good solution.

Last night, I did unplug the VGA cable after I made my post. I was too tired to do further experiments or post again (sorry), but:
It fixed all my problems. The noise disappeared, and I was actually getting the resolution I set as output in the Java KVM session window, instead of being locked to an unusable 640x480 with the video off center.

On closer inspection, the VGA cable I'm using is missing a pin. Apparently, that might be normal on some cables--Pin 9 is often missing. Normally, that's not a problem, as that's supposed to be a ground pin. But in my case, it seems to have been an issue. The output was noisy (not properly grounded) and the unit was mad enough not to be able to set resolution correctly.

The more troubling alternative is that a pin actually broke off; I'll need to check the receptacle on the KVM to make sure nothing's stuck in there.

I need to do some further testing to confirm this was the actual issue, and probably get a new 15 pin VGA cable to test with, as well.

At least the web console is working as expected now. If I had this to do over again, I'd get the unit fully configured before plugging in a display, so I could verify the HTML5 session output was correct. I'd have had to use the serial interface for that, as by default the LAN interfaces are effectively disabled (DHCP is off by default, so they can't pull addresses).

EDIT:
So, I was looking at bad information. Wikipedia is a better source for VGA cable specs: VGA connector - Wikipedia . Pin 9 used to be for keying the connection. It is now a 5V power pin for EDID EEPROM chips in some displays. Remember how the MPU was misidentifying its resolution and reporting as 640x480? Like its EDID was incorrect and it was defaulting to base VGA resolution? Sometimes, pin 13 and 15 play into this functionality as well, depending on the age of the monitior.

This KVM is only about 10-15 years old. It likely has the latest (last) VGA standard, which means it likely expects pin 9 to actually be the EDID PWR pin.

Definitely going to try with a proper cable.

 

[gregsachs]

@gregsachs @Rand__ :

Thanks for your replies. I ran a VGA cable from the KVM itself to a VGA input on a video scaler/input switcher I use (4 HDMI, 2 VGA, DVI, Composite) that's hooked up to a portable 1080p HDMI monitor. I have one monitor and several devices (mostly HDMI) that need to output video, so this has been a good solution.

Last night, I did unplug the VGA cable after I made my post. I was too tired to do further experiments or post again (sorry), but:
It fixed all my problems. The noise disappeared, and I was actually getting the resolution I set as output in the Java KVM session window, instead of being locked to an unusable 640x480 with the video off center.

On closer inspection, the VGA cable I'm using is missing a pin. Apparently, that might be normal on some cables--Pin 9 is often missing. Normally, that's not a problem, as that's supposed to be a ground pin. But in my case, it seems to have been an issue. The output was noisy (not properly grounded) and the unit was mad enough not to be able to set resolution correctly.

The more troubling alternative is that a pin actually broke off; I'll need to check the receptacle on the KVM to make sure nothing's stuck in there.

I need to do some further testing to confirm this was the actual issue, and probably get a new 15 pin VGA cable to test with, as well.

At least the web console is working as expected now. If I had this to do over again, I'd get the unit fully configured before plugging in a display, so I could verify the HTML5 session output was correct. I'd have had to use the serial interface for that, as by default the LAN interfaces are effectively disabled (DHCP is off by default, so they can't pull addresses).

EDIT:
So, I was looking at bad information. Wikipedia is a better source for VGA cable specs: VGA connector - Wikipedia . Pin 9 used to be for keying the connection. It is now a 5V power pin for EDID EEPROM chips in some displays. Remember how the MPU was misidentifying its resolution and reporting as 640x480? Like its EDID was incorrect and it was defaulting to base VGA resolution? Sometimes, pin 13 and 15 play into this functionality as well, depending on the age of the monitior.

This KVM is only about 10-15 years old. It likely has the latest (last) VGA standard, which means it likely expects pin 9 to actually be the EDID PWR pin.

Definitely going to try with a proper cable.

FWIW, I just checked and my server connected via Displayport just shows "Generic PnP monitor", this is what it offers for resultion, plus i thiing 1024x768 and maybe 1280x1024:

 

[John T Davis]

FWIW, I just checked and my server connected via Displayport just shows "Generic PnP monitor", this is what it offers for resultion, plus i thiing 1024x768 and maybe 1280x1024:
View attachment 45330

Thanks!

Is that screenshot from your KVM? Mine looks nothing like that.
Or is it from the server's IPMI?

I'm feeling a bit dumb now--and seriously in need of some battery-operated lights in my rack-space where the KVM installed. I didn't actually have a missing pin on that cable; I'm not sure what I thought I saw.

OTOH, now I own extra VGA cables. -_-

On further testing, what actually solved my issues was setting the KVM itself to pretend to be a 1440 x 900 (900p) monitor (WXGA+ 16:10 resolution).
This is the only 16:10 setting available in the firmware for my MPU4032; everything else is 4:3 or 16:9.

I suspect having the KVM hooked into a variable refresh rate/resolution video scaler instead of an actual VGA monitor is a big part of my issues, but I don't have a VGA monitor.

I'm still hitting an odd issue with Linux servers that just have a TTY (no X or Wayland session).
They have the correct resolution, and the top left and right corners of the output are in the right parts of the display output, but the bottom few lines are getting cut off ... which is a bit of a problem as that's where the latest output and prompts to interact with the machine tend to appear.

I'm pretty sure this is mostly an issue with the scaler not interacting well with the KVM; I'm just not sure what to do with it short of buying a new monitor, which isn't really a practical solution.

I have to hit return 3-5 times on a blank shell prompt to scroll the display.

It's like the servers think the monitor is taller than it actually is.

EDIT: Seting the KVM to report itself as a 1080p monitor (1920x1080p) introduces noise and cuts off the left and right sides, but gets the top and bottom correct when working in Linux. My video scaler is a 1080p model, so it makes sense that it'd be happier with a 1080p signal, but the KVM itself clearly isn't. I suspect that they added 1080p support to the KVM late in its life, and it's not really powerful enough to do it well--at least, not with a setup like mine.

EDIT 2: I've also noticed that BIOS splash screens render correctly. It's only the Linux TTY console itself that goes sideways. Really strange.

 

[gregsachs]

Thanks!

Is that screenshot from your KVM? Mine looks nothing like that.
Or is it from the server's IPMI?

I'm feeling a bit dumb now--and seriously in need of some battery-operated lights in my rack-space where the KVM installed. I didn't actually have a missing pin on that cable; I'm not sure what I thought I saw.

OTOH, now I own extra VGA cables. -_-

On further testing, what actually solved my issues was setting the KVM itself to pretend to be a 1440 x 900 (900p) monitor (WXGA+ 16:10 resolution).
This is the only 16:10 setting available in the firmware for my MPU4032; everything else is 4:3 or 16:9.

I suspect having the KVM hooked into a variable refresh rate/resolution video scaler instead of an actual VGA monitor is a big part of my issues, but I don't have a VGA monitor.

I'm still hitting an odd issue with Linux servers that just have a TTY (no X or Wayland session).
They have the correct resolution, and the top left and right corners of the output are in the right parts of the display output, but the bottom few lines are getting cut off ... which is a bit of a problem as that's where the latest output and prompts to interact with the machine tend to appear.

I'm pretty sure this is mostly an issue with the scaler not interacting well with the KVM; I'm just not sure what to do with it short of buying a new monitor, which isn't really a practical solution.

I have to hit return 3-5 times on a blank shell prompt to scroll the display.

It's like the servers think the monitor is taller than it actually is.

EDIT: Seting the KVM to report itself as a 1080p monitor (1920x1080p) introduces noise and cuts off the left and right sides, but gets the top and bottom correct when working in Linux. My video scaler is a 1080p model, so it makes sense that it'd be happier with a 1080p signal, but the KVM itself clearly isn't. I suspect that they added 1080p support to the KVM late in its life, and it's not really powerful enough to do it well--at least, not with a setup like mine.

EDIT 2: I've also noticed that BIOS splash screens render correctly. It's only the Linux TTY console itself that goes sideways. Really strange.

The screen shot was windows display settings on a kvm-ip session.
If the video scaler is causing confusion, and you are ok with just using the KVM-IP interface, what about using a VGA dummy plug?

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That will fool the KVM into thinking it has a HD display connected.

 

[John T Davis]

The screen shot was windows display settings on a kvm-ip session.
If the video scaler is causing confusion, and you are ok with just using the KVM-IP interface, what about using a VGA dummy plug?

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That will fool the KVM into thinking it has a HD display connected.

I'll definitely look into that. Thanks.

I can just unplug the scaler and go without a real display if necessary. The portable 1080p monitor that the scaler uses as output lives on my desk. That would have been convenient.

The odd thing about all this is that with the scaler connected, it works properly for some devices hooked up to the KVM, but not all of them.

1. I have a Proxmox node (Debian 13) that works fine--except for a few lines at the bottom being cut off.
2. BSD works almost, but the display is slow to refresh and respond to input.
3. A Proxmox Backup Server node (Debian 13) is stuck in 640x480 and several columns on the left side of the screen are cut off. But: It looks perfect in UEFI boot splash and in the BIOS. It doesn't screw up until Linux starts to boot. That makes me think it's a Linux driver issue of some sort.

EDIT: I'm experiencing similar issues with nothing plugged into the VGA output on the KVM. This is a good thing, as far as I'm concerned. That means whatever the problem is, it's not about my real-world video output device.

Slowly but surely, my Linux TTY troubleshooting skills are re-awakening themselves, and I remembered `inxi` exists.

On the Linux machine that's behaving well, when the KVM is set to 1440 x 900 (the available mode that's listed as a supported input resolution in the manual), I get a correct looking output that properly shows the top, bottom, and sides of the screen (nothing is cut off).

Graphics:
  Device-1: Intel AlderLake-S GT1 vendor: Hewlett-Packard driver: i915
    v: 2025.07.22-sriov.6.12.39 alternate: xe arch: Xe process: Intel 10nm
    built: 2020-21 ports: active: HDMI-A-4 empty: DP-1, DP-2, DP-3, HDMI-A-1,
    HDMI-A-2, HDMI-A-3 bus-ID: 00:02.0 chip-ID: 8086:4680 class-ID: 0300
  Display: server: No display server data found. Headless machine?
    tty: 126x74
  Monitor-1: HDMI-A-4 model: Vertiv 60Hz built: 2013 res: 1440x900 gamma: 1.5
    size: 367x230mm (14.45x9.06") modes: max: 1440x900 min: 640x480
  API: EGL v: 1.5 hw: drv: intel iris platforms: device: 0 drv: iris
    device: 1 drv: iris device: 2 drv: iris device: 3 drv: iris device: 4
    drv: iris device: 5 drv: iris device: 6 drv: iris device: 7 drv: iris
    device: 8 drv: swrast gbm: drv: iris surfaceless: drv: iris
    inactive: wayland,x11
  API: OpenGL v: 4.6 compat-v: 4.5 vendor: mesa v: 25.0.7-2
    note: console (EGL sourced) renderer: Mesa Intel UHD Graphics 770 (ADL-S
    GT1), llvmpipe (LLVM 19.1.7 256 bits)
  Info: Tools: api: eglinfo,glxinfo gpu: gputop, intel_gpu_top, lsgpu
    x11: xdriinfo, xdpyinfo, xprop, xrandr

From all that, this is the key:

Monitor-1: HDMI-A-4 model: Vertiv 60Hz built: 2013 res: 1440x900 gamma: 1.5
    size: 367x230mm (14.45x9.06") modes: max: 1440x900 min: 640x480

It's able to auto-detect a working resolution and screen size--though, I had to set the resolution on the KVM, unplug the VGA cable from the server, plug it back in, and reboot the KVM and then the server and I'm still not sure what combination of those got everything to sync up. There's too many moving parts to juggle when it comes to HDMI to VGA to KVM to have confidence about why it works.

On the other Linux server, it's stuck at 720x480 even with the KVM set to 1440x900, and also lists a different virtual monitor size.

Graphics:
  Device-1: Intel JasperLake [UHD Graphics] driver: i915 v: kernel arch: Gen-11
    process: Intel 10nm built: 2019-21 ports: active: HDMI-A-2
    empty: DP-1,HDMI-A-1 bus-ID: 00:02.0 chip-ID: 8086:4e71 class-ID: 0300
  Display: server: No display server data found. Headless machine?
    tty: 159x74
  Monitor-1: HDMI-A-2 model: Vertiv 60Hz built: 2013 res: 1920x1080
    gamma: 1.5 size: 508x285mm (20x11.22") modes: max: 720x480 min: 640x480
  API: EGL v: 1.5 hw: drv: intel iris platforms: device: 0 drv: iris
    device: 1 drv: swrast gbm: drv: iris surfaceless: drv: iris
    inactive: wayland,x11
  API: OpenGL v: 4.6 compat-v: 4.5 vendor: mesa v: 25.0.7-2
    note: console (EGL sourced) renderer: Mesa Intel UHD Graphics (JSL),
    llvmpipe (LLVM 19.1.7 128 bits)

So, this is a Linux frame buffer/display setting issue that I need to sort out.
FreeBSD is, somehow, better at barebones TTY frame buffer stuff. But that doesn't really surprise me, as its domain is almost entirely console-based servers at this point.

Thanks for so patiently helping me through this as I've tried to troubleshoot it. I know I've gone around in circles quite a bit with it.


And on both of them, the BIOS screen and boot splash look perfect.