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Discussion Starter #1

over the course of the last three years i have steadily upgraded the hardware on a mini itx built in a Macintosh SE Case from the late 80´s. The plastic housing is not altered in any way. To achieve a good balance of performance and heat generation i try to limit the source of the latter as much as i can. Sadly the new bios settings on my mainboard and the i9-9900 give me somewhat of a headache to undervolt it properly.

my System:

Bootloader: opencore-version 6.6
macOS: 11.2.1
Mainboard: Gigabyte Z390 I AORUS PRO WiFi
Prozessor: Intel Core i9-9900
Cooler: Noctua NH-U9S
Grafikkarte: Radeon AMD RX 480 8GB (BIOS modded for undervolt operation)
RAM: Corsair Vengeance LPX 2x16GB, DDR4, 3000MHz (run at 2666 MHz)

my Problem:

On stock settings (Vcore at 1.200 V) and no adjustments, stress testing the CPU will get me above 95 ℃ on the CPU Proximity (Intel Power Gadget: Power PKG about 135Watts). When i set CPU Vcore to Normal and use Dynamic Vcore with a value down to -0.120V, I run perfectly fine in stresstesting with max Temperatures at about 80℃ (Power PKG about 110Watts). But this way i get occasional crashes in idle because of Vdroop (if i understood correctly). Any combination of CPU Internal AC/DC Load line Calibration and CPU Vcore Load line Calibration has given my either increased wattage and therefore temperature or instability while stress testing.

Long story short: How can i keep speedstepping and stock frequencies alive, be stable in idle and preferably lower the Vcore under load only?

what i am running on so far:

CPU Vcore set to Normal
Dynmaic Vcore (DVID) set to -0.010V
CPU Internal AC/DC Load line Calibration set to Power Savings
VCCPLL OC from 1.250V to 1.110V

This does give me low temps under load in the 80-85 ℃ region, but still comes with odd occasional crashes (within 1 in 48h) eg. after wake or random idle moments. I did come across mentioning about VCCPLL OC giving false readouts on the temp sensors. I can not confirm that, since i am running an arduino to do the fan controll for the exhaust and graphicscard (with a serial readout). There a two temperature probes, on on the GPU heatpipe and on on the CPU. The temperature readings seem to be in check with the system temp readings).

Any help to properly undervolt a Gigabyte Mainboard with a i9-9900 (no K) would be greatly appreciated.




H₂O Aficionado
4,105 Posts
Off topic but that case cross section / render is beautiful. Is it your render?

2 Posts
Discussion Starter #3
@Slaughtahouse thx - i modelled the Macintosh SE case and all its components in Fusion 360 - This enabled me to play Tetris with the different accessories and design the required mounts, brackets, shrouds, etc. - I went through different itx Mainboards and Graphics cards and therefore several iterations of custom shrouds - at the beginning in aluminium and later on, printed versions in PETG.

Gigabyte GA-H270N-WIFI
Gigabyte GA-Z390I-WIFI

Graphics Cards:
Sapphire Pulse ITX Radeon RX 570 4GB
HP AMD Radeon RX 580 4GB <- actually they are dupes and just plain 480s
AMD Radeon RX 480 8GB

I never had an easier time getting pretty renderings with little to no effort - no special light rigging or complex render settings - just some repositioning of the generic light source and a little correction to the exposure. The outcome is dependent of the choice in material appearance and texture. This again, is covered well by the basic library the program offers.




By the way, any help to properly undervolt a Gigabyte Mainboard with a i9-9900 would still be greatly appreciated.
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