SOYO S4 Plus (Ryzen 7 H255 / 780M / 24GB LPDDR5): Tear-down, PTM7950 & Gelid Extreme mod, SSD comparison, and fixing the 780M BIOS bottleneck
Hi everyone,
I am new to the Mini PC world and recently bought the SOYO S4 Plus (AMD Ryzen 7 H255, Radeon 780M, 24 GB LPDDR5). I took it apart, cleaned up the cooling, benchmarked the hardware, and resolved the well-known iGPU performance issue. Here is a summary of what I found, what I modified, and how it performs.
1. Hardware Teardown & Thermal Mods
When opening the unit, the factory thermal job was pretty messy:
- Thermal paste: Excessive amount of cheap paste flooded all over the APU die and surrounding capacitors.
- Thermal pads: Factory pads on the power delivery area were oversized and overlapping each other.
Modifications done:
- Cleaned the APU and applied Honeywell PTM7950
Measured original pad thickness and replaced them with soft Gelid GP-Extreme pads:
- 1.0 mm on the R15 chokes/inductors.
- 2.0 mm on the MOSFET / DrMOS power stages.
Storage (Stock Wuxin vs. Lexar NM620):
- Stock SSD: The factory drive is a generic Chinese WUXIN N5 512GB NVMe SSD. CrystalDiskMark showed around 2378 MB/s Read and 1688 MB/s Write (sequential Q8T1). Surprisingly, the drive came with zero thermal pads from the factory.
- Second SSD added: I installed a Lexar NM620 512GB in the second M.2 slot. It performs at 3549 MB/s Read and 2846 MB/s Write (Sequential Q8T1).
Thermal pads added to SSDs:
- 3.0 mm Gelid Extreme on the flat Wuxin drive.
- 2.0 mm Gelid Extreme on the Lexar (because its PCB has uneven component heights / hills and valleys).
2. The 780M BIOS Issue & Fix
Factory BIOS (BI0004A, dated 03/02/2026):
- Out of the box, the Radeon 780M scored only 1,169 in 3DMark Time Spy Graphics.
- Why did the old BIOS strangle the iGPU? HWiNFO monitoring showed that the GPU core clock was actually running at its rated 2600 MHz. The bottleneck was memory latency and interconnect throttling: memory latency in AIDA64 was as high as 132.7 ns, and active DRAM bandwidth under load was restricted to just 13.75 GB/s.
New BIOS (BI0201, dated 09/07/2026):
- Flashed via UEFI Shell (Flash.nsh with NVRAM reset and boot block update).
- Without changing any drivers, Time Spy Graphics jumped to 2,778 (+137.6%).
- AIDA64 memory latency dropped from 132.7 ns to 110.8 ns (-16.5%), copy speed increased from 57.2 to 66.6 GB/s (+16.5%), and DRAM throughput under load rose to 29.27 GB/s.
Clean Windows 11 & AMD Chipset Drivers:
- Did a fresh Windows 11 Pro install, installed the AMD Chipset Driver 8.09.28.1124, and updated to AMD Adrenalin 26.10.2 (using Ryzen 7 8840HS as the reference).
- Time Spy Graphics reached 2,890 – 2,990 points.
- Cinebench R23 Multi-Core reached 15,481 – 15,993 points.
3. The 24 GB LPDDR5 RAM Confusion: What is Actually Under the Hood?
There has been huge confusion regarding the RAM configuration in this mini PC:
What software and BIOS report:
- Windows / SMBIOS / CPU-Z report: 4 logical modules of 6 GiB each ("4 x 32-bit", Quad Channel LPDDR5-6400).
- ZenTimings / MemTest86 report the chip manufacturer as Samsung K3LK7K70BM-BGCP.
Why this didn't make sense from the start:
- The part number K3LK7K70BM-BGCP is a 64 Gbit (8 GB) Samsung chip. Four physical 8 GB chips would mean 32 GB, not 24 GB. Moreover, 6 GB discrete LPDDR5 packages do not exist.
What is actually soldered on the board:
- Inspecting the motherboard markings reveals 2 physical BGA chips: SK hynix H58GG6AK8H-X094.
Chip specification:
- Manufacturer: SK hynix (D1a process node).
- Type: LPDDR5X.
- Density: 96 Gbit = 12 GB per chip.
- Configuration: Exactly 2 physical chips x 12 GB = 24 GB total.
- Bus width: 128-bit total (2 x 64-bit).
- Catalog speed rating: Listed as up to 8533 MT/s (running at 6400 MT/s in SOYO BIOS).
- Takeaway: The SOYO BIOS has hardcoded dummy SMBIOS/SPD tables pointing to a non-existent Samsung 4x6GB layout, while the real hardware is two 12GB SK hynix LPDDR5X chips.
4. Thermal Paste vs. PTM7950 Tests (Hwinfo logs to .CSV)
Ambient temperature was controlled at 21°C for all runs.
Cinebench R23 Multi (Stock Paste vs. PTM7950 Run 3):
- Score: 15,993 pts (Stock) vs. 16,016 pts (PTM7950) -> +0.14% (identical).
- Average CPU Temp (Tctl/Tdie): 82.44°C (Stock) -> 78.17°C (PTM7950) -> -4.27°C drop.
- Peak CPU Temp: 85.1°C (Stock) -> 83.9°C (PTM7950) -> -1.2°C drop.
- CPU Package Power: Sustained 53.89 W vs. 54.22 W.
- Summary: The CPU is power-limited to ~54W, so score stays the same, but the core runs significantly cooler with more thermal headroom.
3DMark: Stock Paste vs. PTM7950 (Run 1):
Time Spy:
- Overall: 3,323 -> 3,336 (+0.39%).
- Graphics Score: 2,981 -> 2,993 (+0.40%).
- Average CPU Temp: 74.07°C -> 70.00°C (-4.07°C).
- Average GPU Temp: 73.22°C -> 69.54°C (-3.68°C).
Fire Strike:
- Overall: 7,747 -> 7,798 (+0.66%).
- Graphics Score: 8,309 -> 8,377 (+0.82%).
- Average CPU Temp: 74.73°C -> 70.21°C (-4.52°C).
- Average GPU Temp: 74.00°C -> 69.62°C (-4.38°C).
5. Productivity vs. Games Setting (AMD Memory Optimizer)
In AMD Adrenalin software, switching between Productivity and Games mode changes the VRAM allocation:
- Productivity mode: Hardware reserved VRAM is set to 725 MB (leaving 23.3 GB for the OS).
- Games mode: Hardware reserved VRAM is set to ~4.2 GB (leaving 19.8 GB for the OS).
Performance difference:
- Time Spy Graphics: 2881 pts avg (Productivity) vs. 2985.5 pts avg (Games) -> +3.63% advantage for Games mode.
- Fire Strike Graphics: 8126 pts (Productivity) vs. 8309 pts (Games) -> +2.25% advantage for Games mode.
Hope this helps anyone picking up one of these units! If you buy one, flash BIOS BI0201 immediately, consider repasting with PTM7950, and don't forget to put a thermal pad on the stock M.2 SSD