Seasonic has warned of a compatibility issue between its Focus Plus-branded power supplies and selected Nvidia and AMD graphics cards, potentially resulting in system shutdowns during periods of heavy load - and its test information suggests it has known about the issue since January.
Designed to sit towards the upper end of the company's range, the Focus Plus power supply family is aimed at gamers - which makes Seasonic's admission of an apparent compatibility issue between the PSUs and selected graphics cards doubly embarrassing. The first of two, seemingly related, issues is relatively minor: The company has confirmed that one particular Nvidia graphics card, the Asus GeForce GTX 970 Strix, interacts with the power supplies in such a way as to cause the occasional black screen during heavy usage. This, Seasonic claims, is due to a small number of these cards emitting 'higher than normal ripple while under heavy load', and can be fixed by using PCI Express cables with thicker-than-normal shielding.
The second compatibility issue is rather more concerning, and seems to point to a flaw in the design of the power supply family: PSUs manufactured prior to January 2018, Seasonic admits, may spontaneously shut down when used with AMD Vega 56 and 64 graphics cards. Triggered, again, by high GPU load, the problem this time is blamed on 'higher than normal peak current emitted [sic] by this particular range of GPUs' which triggers the power supply's internal cut-off - with figures given by the company suggesting a 51A peak for a single Vega 56 and 102A for a two-card CrossFire setup over a period of around 10 milliseconds. PSUs manufactured after January 2018, the company has confirmed, have a less-sensitive protection trigger, though it still advises that buyers running high-end graphics cards 'choose to purchase other power supplies with higher power ratings to ensure that the computer works properly'.
That Seasonic has known of the issue since at least January seems clear: As well as having modified the trigger to be less sensitive at this time, the company's test documentation shows that the peak-current test was carried out in January 2018. Why it has taken Seasonic from January to the end of November to alert customers to the problem is not known.
In both cases, Seasonic's advice is the same: Contact the company for further assistance, with the company confirming that it will supply new PCI Express power cabling where required though stopping short of promising a swap to a newer PSU for those encountering the Vega compatibility issue. More details, the majority in Chinese, are available on the company's knowledge base.