NVIDIA Fixed Fan-Speed Bug in AD103 & AD104 GPU Silicon For RTX 4080 & RTX 4070 Ti


When we revealed that two distinctive GPUs, the AD104-250 and AD104-251, would go into commercial production later this quarter, we first heard whispers regarding the new NVIDIA Ada Lovelace GPU hardware. According to earlier speculations, the new GPUs will do away with a comparator circuit and even reduce the BOM costs by $1, according to HKEPC. It turns out that this is accurate, but removing the circuit shouldn’t improve the card’s effectiveness in any way; instead, it should correct a critical flaw.

The regular AD103-300 and AD104-250 GPU cores were included with the initial NVIDIA GeForce RTX 4080 and RTX 4070 Ti graphics cards. We are currently supplying both of these cards with a newer AD103-301 & AD104-251 silicon, some of which are already on the retail market.

Old NVIDIA Ada GPUs with a “U121” Labeled Comparator Circuit (Image Credits: Igorslab):

The biggest difference between the two silicon iterations is actually a problem with the fan speed management. In order to ensure that the fan starts spinning and hits a required set of operating tasks, the first version of the Ada GPUs had to incorporate external comparator circuits, identified as ‘U121’ on the PCB. Igorslab explains the following:

The second piece of advice comes from the notebook industry, where even chips with bugs may be utilised without any issues because the problematic area is typically replaced by a system with an integrated controller. This puts us closer to the bug, which is equally unimportant and trivial: It relates to the section with the alleged “initial fan speed.” At a predetermined hotspot temperature, does the fan begin to spin safely or not? Or does the fan stop or have a fault? With an external comparator, the AD103-300 or AD104-250 precisely solves this function by comparing the PWM signal for fan control with the actual value. Even when you measure, you can see that.

from Igorslab

All new NVIDIA GeForce RTX 4080 & RTX 4070 Ti graphics cards won’t need to rely on the comparator external circuit anymore because this problem has been fixed in the new Ada GPU silicon, and since it isn’t a particularly important component, it can easily be removed with only a minor adjustment to the BOM. While $1 may not seem like much, every penny counts when you are creating hundreds or even tens of thousands of cards per month.


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