anexanhume
Member
Eurogamer (via pocketnews) has posted an article covering the new PS4 model that debuted in Japan first. It covers the motherboard changes as well as new power measurements and ambient noise measurements.
There are many significant changes, the most important going from clamshell mode GDDR5 (16 modules, sharing address/data lines in pairs) to non-clamshell with 8 modules. Power consumption has also dropped 26W from the launch model while playing a game.
The move to 8 8Gb GDDR5 modules was expected, but the drop in power consumption was perhaps not, especially since the reports noted that the package/die measurements stayed constant. Both sites correctly theorize that the reduction in GDDR5 modules plays into it, but that alone cannot explain the 26W load drop. Samsung's product offering charts (pdf warning) show that the previous GDDR5 modules and the new ones run at the same voltage, meaning mW per bit has likely not changed drastically. The articles theorize that the APU may be on an alternate 28nm node, but that seems far-fetched to explain the large gulf between the power numbers. Assuming power supply efficiency has stayed relatively constant, it likely only accounts for ~3W of the savings (88% efficiency at peak).
We can see from anandtech and this chart that a 18% drop in power consumption in between revisions is equal to those seen in revisions with die shrinks. It is completely possible that the chip designers would elect to keep the same die padout to retain package characteristics, and potentially port more existing design work from one motherboard revision to the next, if the smaller die (and thus a smaller reticle for more dies per wafer) was not the primary objective of the shrink. Less power consumption allows everything to shrink, decreasing cost and increasing reliability. On the other hand, it makes sense to maintain the physical case size as molds are fairly expensive. Microsoft elected to keep the same case until the Valhalla revision of the Xbox 360, for example. Given the cost of new nodes rising, a die with same dimensions would go up in cost compared to 28nm, which is a detracting factor to a possible process only shrink.
The question of a die shrink becomes potentially problematic in that we know TSMC produced the first APU for the PS4. AMD, along with Nvidia, are skipping the 20nm node for graphics products, meaning this shrink would have been a custom job with no ability to re-use shrunken assets from their graphics products. In fact, AMD confirmed today that they are skipping 20nm entirely. TSMC's 16nm FinFET is only in the initial stages of production, with volume likely only just starting up. They are behind Samsung in that regard, whose 14/16 FinFET are already in the latest Galaxy flagship phone. It could be that AMD has thrown a curveball and transitioned to the shared Samsung/Glofo process, but that also seems unlikely given GPU makers' strong reliance on TSMC node variants for their graphics products.
Another important point to note is that standby power has decreased by as much as 50%. This strongly indicates a process change of some sort as leakage has reduced significantly. Perhaps different variants of the 28nm offerings could create such a significant difference, but there's no product on the market that was known to go through such a transition to compare. It seems likely that some power gating would need to be involved to achieve the lower standby power, and a significant nominal voltage reduction (greater than 10%) to achieve drop in consumption at peak load. Unfortunately, I don't know enough about TSMC's 28nm process variants to make further educated comments on the matter.
Also, there does not appear to be a fix of the companion processor that turned out to be insufficient for standby downloads. Standby download power is still nearly 60W. It seems we may need something along the lines of Chipworks' gate pitch analysis to determine the process used.
Image of the new motherboard (Top side)
Image of the old motherboard (Top side, from iFixIt)
note: I can post more images upon request to break up the text, but wanted to encourage people to click through to the links to give the content creators their pageviews.
There are many significant changes, the most important going from clamshell mode GDDR5 (16 modules, sharing address/data lines in pairs) to non-clamshell with 8 modules. Power consumption has also dropped 26W from the launch model while playing a game.
The move to 8 8Gb GDDR5 modules was expected, but the drop in power consumption was perhaps not, especially since the reports noted that the package/die measurements stayed constant. Both sites correctly theorize that the reduction in GDDR5 modules plays into it, but that alone cannot explain the 26W load drop. Samsung's product offering charts (pdf warning) show that the previous GDDR5 modules and the new ones run at the same voltage, meaning mW per bit has likely not changed drastically. The articles theorize that the APU may be on an alternate 28nm node, but that seems far-fetched to explain the large gulf between the power numbers. Assuming power supply efficiency has stayed relatively constant, it likely only accounts for ~3W of the savings (88% efficiency at peak).
We can see from anandtech and this chart that a 18% drop in power consumption in between revisions is equal to those seen in revisions with die shrinks. It is completely possible that the chip designers would elect to keep the same die padout to retain package characteristics, and potentially port more existing design work from one motherboard revision to the next, if the smaller die (and thus a smaller reticle for more dies per wafer) was not the primary objective of the shrink. Less power consumption allows everything to shrink, decreasing cost and increasing reliability. On the other hand, it makes sense to maintain the physical case size as molds are fairly expensive. Microsoft elected to keep the same case until the Valhalla revision of the Xbox 360, for example. Given the cost of new nodes rising, a die with same dimensions would go up in cost compared to 28nm, which is a detracting factor to a possible process only shrink.
The question of a die shrink becomes potentially problematic in that we know TSMC produced the first APU for the PS4. AMD, along with Nvidia, are skipping the 20nm node for graphics products, meaning this shrink would have been a custom job with no ability to re-use shrunken assets from their graphics products. In fact, AMD confirmed today that they are skipping 20nm entirely. TSMC's 16nm FinFET is only in the initial stages of production, with volume likely only just starting up. They are behind Samsung in that regard, whose 14/16 FinFET are already in the latest Galaxy flagship phone. It could be that AMD has thrown a curveball and transitioned to the shared Samsung/Glofo process, but that also seems unlikely given GPU makers' strong reliance on TSMC node variants for their graphics products.
Another important point to note is that standby power has decreased by as much as 50%. This strongly indicates a process change of some sort as leakage has reduced significantly. Perhaps different variants of the 28nm offerings could create such a significant difference, but there's no product on the market that was known to go through such a transition to compare. It seems likely that some power gating would need to be involved to achieve the lower standby power, and a significant nominal voltage reduction (greater than 10%) to achieve drop in consumption at peak load. Unfortunately, I don't know enough about TSMC's 28nm process variants to make further educated comments on the matter.
Also, there does not appear to be a fix of the companion processor that turned out to be insufficient for standby downloads. Standby download power is still nearly 60W. It seems we may need something along the lines of Chipworks' gate pitch analysis to determine the process used.
Image of the new motherboard (Top side)
Image of the old motherboard (Top side, from iFixIt)
note: I can post more images upon request to break up the text, but wanted to encourage people to click through to the links to give the content creators their pageviews.
