- Joined
- Apr 24, 2020
- Messages
- 2,724 (1.60/day)
It is not in my priorities of me to discover NVIDIA's magic oompa-loompa inside chip, because I do not make money from VGA card repairs.
I am aware of your measuring gear, but your accident did stop your exploration at the discovery of what an 8846A can do as by far most modern design.
Anyway this is another story, and a boring one for the readers of this forum.
While @TiN is being a bit aggressive with his words, I ultimately believe he's making the correct point.
From a PDN perspective, the only thing that matters is the frequencies at which power is drawn. It doesn't matter how NVidia's pipelines or local memory or whatever work. What matters is that they draw power at 2.1GHz increments, generating a 2.1GHz "ring frequency" across the power network... at roughly 100+ Amps.
Which will be roughly:
* 2.1GHz (Clockspeed of GPU)
* 5.25 GHz (rough clockspeed of the GDDR6x)
* 75Hz (The 75-Hz "pulse" every time a 75Hz monitor refreshes: the GPU will suddenly become very active, then stop drawing power waiting for VSync).
* Whatever the GHz is for PCIe communications
* Etc. etc. (Anything else that varies power across time)
Satisfying the needs of both a 5GHz and 75Hz simultaneously (and everything else) is what makes this so difficult. On the one hand, MLCC is traditionally considered great for high-frequency signals (like 5GHz). But guess what's considered best for low-frequency (75Hz) signals? You betcha: huge, high ESR Aluminum caps (and big 470 uF POSCAPs or 220uF caps would similarly better tackle lower-frequency problems).
----------
COULD the issue be the 2.1GHz signal? Do we KNOW FOR SURE that the issue is that the PDN runs out of power inside of a nanosecond?
Or is the card running out of power on VSyncs (~75Hz)? If the card is running out of power at that point, maybe more POSCAPs is better.
I wouldn't be convinced MLCC is "better" until someone posts a sub-nanosecond transient on a $50,000 10GHz oscilloscope showing the problem. Heck, I've seen no actual evidence posted in this entire discussion that even suggests the PDN is the issue yet. (Yeah, EVGA says they had issues when making the card. But other companies clearly have a different power-network design and EVGA's issues may not match theirs).
Last edited: