TIM instead of soldering inside cheap desktop processors
Last month AMD introduced a new budget processor for the AM5 platform, the Ryzen 5 7400F. It should cost even less than the 7500F, but it’s still a full-fledged Zen 4 hexa-core with 32MB of cache and PCIe 5.0 ×16 support for the GPU, so price-wise it’s probably AMD’s best candidate for an affordable non-AM4 gaming PC. It does seem to have one drawback that sets it apart from more expensive models, though.
When information about this processor surfaced, we examined its specifications and found no limitations compared to the Ryzen 5 7600 and 7500F models, except for its lower clock speed. As an “F” model, it also has its integrated GPU disabled, but this is already the case for the 7500F as well. However, there is a compromise. The processor has already reached some users, and in China, one buyer delidded it in his review, meaning they removed its metal cover, also known as the heat spreader. During this process, they discovered that the 7400F does not have its heat spreader soldered on but instead uses a cheaper solution with simple thermal grease or paste (conventional TIM), unlike other Ryzen 7000 models.
Using paste in this role results in worse heat transfer from the silicon to the cooler compared to using indium solder TIM (which is used in higher-end Ryzen 7000 models), meaning the processor will reach higher temperatures under load. This does appear to be the case for the Ryzen 5 7400F, despite being a 65W processor with a maximum boost power consumption of 88W. In multi-threaded applications that bump into this limit, the processor reportedly hit temperatures of up to 95 degrees Celsius, even when cooled with an AIO liquid cooler (although the ambient temperature, which may influence things, was not specified).
Thermal grease replacing solder TIM, therefore, has a noticeable negative impact even on a 65W model, and its use in this processor seems to be close to testing the limits (unless the reviewer made a mistake, such as improper cooler installation – hopefully, more reviews will emerge over time to clarify the situation, if this is the case). However, when gaming, CPU load is usually not at 100%, so temperatures should be more manageable for most users.
High temperatures do not imply increased power consumption in this case. Their cause is that heat dissipation in these chiplet-based processors is limited by the very small surface area of the 5nm silicon (which should have an area of just 66.3 mm²), making transferring the heat away a challenge even with a soldered heat spreader. With thermal paste, this “penalty” worsens due to both the small heat transfer area and the lower thermal conductivity.
The surface area factor is why thermal paste is less of an issue in non-chiplet processors with large monolithic silicon die (as long as their power consumption is not too high), such as Intel’s 65W Core i5 models.
Whether this cost-cutting measure is worth it remains a question. If it helped lower the processor’s price, then perhaps it is. It seems that in China, the processor costs the equivalent of just about 115 USD, which is quite cheap for the AM5 platform. This would currently be around 134 € incl. 21% VAT in Europe. That means the savings compared to the Ryzen 5 7500F, the closest alternative without the thermal paste issue, are already significant, as that model starts at around 165 €. It is even cheaper than the Ryzen 5 8400F, which, however, is not very suitable for gaming due to its reduced L3 cache and lack of PCIe lanes for the graphics card.
However, we are still waiting to see if the Ryzen 5 7400F will be available for purchase in our market, so actual european prices cannot be compared yet.
Will cheaper thermal material be used in more processors?
The fact that the Ryzen 5 7400F uses thermal paste is interesting because AMD previously maintained the same design across an entire processor family to avoid complicating manufacturing. This meant that either paste or solder was used consistently in both budget and high-end models. However, for chiplet-based processors on the AM5 socket, this seems to no longer the case, apparently AMD has managed to accomodate both soldered and paste-based workflows in the production line.
This raises the possibility that this cost-saving measure might appear in more desktop Ryzen processors in which we wouldn’t have expected it before – such as in the Ryzen 5 9600. (For APUs like the Ryzen 5 8400F or Ryzen 5 8500G, the use of paste is not a surprise, as it has been the usual solution in that category due to their different design with a larger monolithic silicon die.) So far, no one has delidded a Ryzen 5 9600, this processor has also not yet appeared in european stores.
Source: Bilibili (1, 2) Tom’s Hardware
English translation and edit by Jozef Dudáš
⠀
