Raspberry Pi 4 推出 8GB 版本

Raspberry Pi 宣佈了 8GB 版本：「8GB Raspberry Pi 4 on sale now at $75」。

除了記憶體變成 8GB 以外，也因為記憶體加大而需要更多電力，所以電供元件的部份也跟著改動，然後也提到 COVID-19 造成的延遲：

To supply the slightly higher peak currents required by the new memory package, James has shuffled the power supply components on the board, removing a switch-mode power supply from the right-hand side of the board next to the USB 2.0 sockets and adding a new switcher next to the USB-C power connnector. While this was a necessary change, it ended up costing us a three-month slip, as COVID-19 disrupted the supply of inductors from the Far East.

超過 4GB 的時候一定會檢視 32-bit 與 64-bit 環境的差異，所以就會發現，在預設的 kernel 因為使用 32-bit LPAE (ARM 上的 PAE)，所以雖然是有機會可以使用到 8GB，但單一程式會有 3GB 限制：

Our default operating system image uses a 32-bit LPAE kernel and a 32-bit userland. This allows multiple processes to share all 8GB of memory, subject to the restriction that no single process can use more than 3GB.

目前如果想要原生支援 64-bit 環境的話，需要使用其他作業系統：

But power users, who want to be able to map all 8GB into the address space of a single process, need a 64-bit userland. There are plenty of options already out there, including Ubuntu and Gentoo.

不過另外官方也在測自家的 64-bit 版本，已經有 early beta 版本可以測試看看了 (話說 early beta 這個詞，可以解釋成 alpha 的品質...)：

Not to be left out, today we’ve released an early beta of our own 64-bit operating system image. This contains the same set of applications and the same desktop environment that you’ll find in our regular 32-bit image, but built against the Debian arm64 port.

不過上面的 Chromium 與 Firefox 不完整支援硬體解壓影片的部份還是痛，四代的 CPU 在 YouTube 上是可以硬撐 1080p30 解碼，但畫面順暢度就不太行了，客廳還是用老 Mac Mini (2011 的版本) 來撐場...