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• #6777 Petykemano veterán

  Új Válasz 2022-04-12 09:42:05 #6777

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  Petykemano

  veterán

  AMD N7=>N5
  Mi magyarázhatja, ha az AMD 2x-es tranzisztorsűrűséget ér el?
  
  "In my mind what is more interesting would be how much tradeoffs AMD would have to make this time, or rather what things they need not have to sacrifice this time.
  Even if AMD did not go with a 3 fin design with N7, they made a lot of the cells taller and increased the number of tracks in order to get the needed drive performance for ~5GHz operation. (I think it is 2x poly)
  This degraded density, and the taller cells also degrade RC characteristics leading to lower energy efficiency.
  Then there are those additional metal layers needed to deliver the signals and power which is necessitated by the high frequency design which also introduced additional RC losses. If I remember well, all the way to 19 metal layers compared to 13-14 for mobile SoCs.
  If on their custom N5 they can go with standard 2 fin layout with compact/shorter cells and keeping more or less similar frequency it would already be a big leap. Far higher efficiency than what TSMC is advertising for N7--> N5 transition because basically the N7 customizations AMD made nerfed efficiency in no insignificant amount.

  The other double whammy is that the taller cells cut density a lot, so if they can stick to a compact 2 fin cell layout on N5 would really boost Xtor density allowing a greater density gain than TSMC's advertised gains for N7-->N5 transition. (In performance optimizations the cells can go almost 30% larger than usual)

  This was the reason I found that Zen 4 process reveal from last year's accelerated DC event to be interesting, it indicated that they indeed did not have to sacrifice density and efficiency much and because of reasons above got better gains vs N7 than TSMC's N7-->N5 transition (using mobile as standard)
  They will gain base frequency and all core frequency simply due to being more efficient. And the density gain is a wild card, it is very plausible that they literally meant it when they said 2x density gain. which could be up to 60% MTr gain for a Zen 4 CCD with the rumored die sizes. What are they doing with so much more MTr on a arch refresh?"
  [link]

  Azt én is szoktam mondani, hogy a magas frekvencia elérése nincs ingyen és hogy tranzisztorsűrűséget veszít vele egy design. Ez egy eléggé hozzáértőnek tűnő magyarázat a jelenségre.

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