New Raspberry Pi 4 VLI Firmware Lowers Temperature by 3-5°C

The other day I tested Raspberry Pi 4 with an heatsink since previous multi-threaded benchmarks clearly made the board throttle when running those without any cooling solution.

The guys at the Raspberry Pi Foundation somehow noticed my post, and I received an email from Eben Upton explaining a new Raspberry Pi 4 VLI firmware had “some thermal optimizations that are not installed by default on early production units.” I did not understand VLI at first, but eventually understood this referred to the firmware for VIA VL805 PCIe USB 3.0 controller on the board.

The Raspberry Pi Foundation provided me with a test version of the firmware, which they’ll release in the next few days, or weeks after testing is completed.

Now if you’re going to test a platform that will throttle due to overheating, it’s very important you do so at constant room temperature. I work in a office where the air conditioner is set to 28°C, so that’s about the temperature I have here.

Before going on with the test I’ve installed rpi-monitor to have nice CPU temperature charts later on:


Let’s run sbc-bench without heatsink with old VLI firmware (version 00013701):


7-zip never completed, as it was killed three times due to running out of memory. Maybe it happened because with a 1GB RPi 4, we’re right at the limit. Enabling ZRAM may help.

But we do have our temperature data for the full benchmark. We started at 67°C idle, and the spike to over 80°C (11:26 to 11:30) is exactly during 7-zip multi-threaded benchmark:

Raspberry Pi 4 SBC Bench Temperature
Tempeature during sbc-bench – Click to Enlarge

Now let’s install the firmware in a terminal in the Raspberry Pi 4:


For reference the tool can also be used to backup the firmware, and write to any location in the EEPROM:


If you mess up you’ll lose USB connectivity, but user could have to ssh or serial into the device and re-run the tool to flash an older firmware to recover. It’s unclear whether early adapter will have to update the firmware manually, or it will be done automatically as part of the update process. That’s one of the reason I can’t share the files now.

Raspberry Pi 4 VLI Firmware Idle Temperature
Click to Enlarge

Nevertheless it does seem to have some effect on idle temperature. Previously I got just under 65°C, but now I get just above 61°C once it stabilizes, so the new firmware does lower the temperature by 3 to 4°C thanks to lower power consumption. Sadly, I can’t measure the latter as my power meter is dead.

Now let’s run sbc-bench again without heatsink and the new VLI firmware (version 0137a8):


This time all three runs for 7-zip could complete for some reasons, and while throttling still did occur, it did to a lesser extent, and the temperature was clearly lower during to single thread benchmarks (~70°C vs 75°C with old firmware).

Raspberry Pi 4 VLI-805 Firmware Temperature
Click to Enlarge

For reference, 7-zip benchmark score with heatsink averaged 5,397 points, without heatsink + old VLI firmware 4,423 points, but the “no heatsink with new VLI firmware” results are much better at 5,298 points. You’ll also note the first two runs were as good as the results with heatsink, but the last one dropped to just under 5,000 points, so for full load under and extended period of time a heatsink is still recommended for full performance. It’s still impressive what a new firmware can achieve.

You may wonder what the Raspberry Pi Foundation has changed. Thomas Kaiser may have found the reason in advance, as now ASPM (Active-State Power Management) seems to be enabled:


This was not the case with the old VLI firmware. The full lspci output can be found here.

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