NVIDIA recently started shipping its GeForce RTX 4080 & RTX 4070 graphics cards with revised AD103 & AD104 'Ada' GPU silicon. A report from Igor's Lab suggests that these aren't meant to improve the card but to resolve a potential bug.
NVIDIA Has New GPUs For Its GeForce RTX 4080 & RTX 4070 Graphics Cards That Resolve Fan-Speed Bug
We started hearing rumors about the new NVIDIA Ada Lovelace GPU silicon when we reported about two unique GPUs, the AD104-250 and AD104-251, going into mass production later this quarter. Earlier rumors claimed that the new GPUs will get rid of a comparator circuit and even lower the BOM costs by $1, as indicated by HKEPC. As it turns out, this is true but the removal of the circuit shouldn't help the efficiency of the card in any regard but instead fix of crucial bug.
The initial NVIDIA GeForce RTX 4080 and RTX 4070 Ti graphics cards shipped with the standard AD103-300 and AD104-250 GPU cores. We now have a newer AD103-301 & AD104-251 silicon in production and shipping with both of these cards, several of which are already available in the retail market.
Old NVIDIA Ada GPUs With Comparator Circuit marked with 'U121' Label (Image Credits: Igorslab):
The main change between the two versions of the silicon happens to be an issue with how the fan speed was controlled. To address this issue, the initial version of the Ada GPUs had to use external comparator circuits, marked as 'U121' on the PCB, to make sure that the fan starts spinning and hit a required set of operational tasks. The following is explained by Igorslab:
The second tip came from the notebook sector, where even the chips with a bug can be used without any problems because the affected area is generally replaced by a solution with an embedded controller. This brings us closer to the bug, which is as trivial as it is important: It’s about the part with the so-called “initial fan speed”. Does the fan start spinning safely at a preset hotspot temperature or not? Or is the fan defective or does it stop? Exactly this function is solved with the AD103-300 or the AD104-250 with an external comparator, which compares the PWM signal for the fan control with the actual value. You can even see that when you measure.
With this issue fixed in the new Ada GPU silicon, all new NVIDIA GeForce RTX 4080 & RTX 4070 Ti graphics cards will not have to rely on the comparator external circuit anymore and since it isn't that major of a component, it can easily be removed while resulting in a small adjustment to the BOM. Now $1 may not sound like much but when you are producing cards in the thousands or even tens of thousands range, every little penny matters for operational cost.