Tag: power

用馬鈴薯判斷電極的正負...

在 Hacker News Daily 上看到「“You don't have a voltmeter. Do you have a potato?” (diy.stackexchange.com)」這則討論，原討論在「Is white wire with grey stripes positive or negative wire?」這邊，有人問了一個問題，說手上有一個交流轉直流的變壓器，想要重新接線到下面這種端子，但不確定變壓器輸出的兩條線裡面，正極與負極分別是哪條：

下面的答案很厲害啊，開頭先說如果你沒有伏特計 (像是三用電錶)，那手上有沒有馬鈴薯：

You don't have a voltmeter. Do you have a potato?

把馬鈴薯切半，把 DC 端的兩條線插到同一顆馬鈴薯上面，大約相距 2cm，插電不久後就可以看到有一端會變綠，那端就是正極，把本來插到馬鈴薯上的端子剪掉後再接線就可以了：

With the power adapter unplugged from your electrical outlet, cut the wires, strip a little insulation from the ends, twist the strands of each wire into a point. Do not allow the bare wires to touch each other from this point on.

Cut the potato in half. Take one half, and poke both wires into the cut face of the potato about 2 cm apart. Plug in the power adapter to the wall outlet. In a short time, the potato around one of the wires will turn green. That is the positive wire.

Unplug the adapter and clip off the ends of the wires so you have clean wire for soldering your new plug.

不確定產生的是不是銅綠，但能給出這種解法的確很有娛樂性 XDDD

去年 OVH 機房大火的部份情形最近被揭露

去年三月在「OVH 法國機房 SBG2 火災全毀」這邊有提到 OVH 的機房大火事件，最近有些情況總算被揭露出來了。

在 Hacker News 上看到「OVHcloud fire report: SBG2 data center had wooden ceilings, no extinguisher, and no power cut-out」這篇這個月月初的報導，裡面題到了一些情形。另外對應的討論在「OVHcloud fire: SBG2 data center had no extinguisher, no power cut-out (datacenterdynamics.com)」這邊可以看到。

其中一個是在講消防隊花了三個小時才把電力切斷，因為電力室外面有非常強力的電弧：

According to the report firefighters on the scene found electrical arcs more than one meter long flashing around the door to the power room, and it took three hours to cut off the power supply because there was no universal cut-off.

另外電力室本身的設計也不利於防火 (木造天花板？)，而且電力管道也沒有隔離：

The power room had a wooden ceiling designed to withstand fire for one hour, and the electrical ducts were not insulated.

另外因為節能的設計，他們設計了多個通道讓外部的空氣容易進入 data center 交換熱量，但這也導致了火苗很不容易熄滅：

Once the fire escaped from the power room, it grew rapidly. The report says that "the two interior courtyards acted as fire chimneys". JDN claims the spread of fire may have been accelerated by the site's free cooling design, which is designed to encourage the flow of outside air through the building to cool the servers.

OVH 目前因為訴訟的關係，基本上都是拒絕評論...

立端科技的 IIoT-I530

因為工作的關係，所以會關注一些特殊的硬體，但好像暫時找不到地方放，就丟在 blog 上面記錄好了...

這次看到的是支援一堆 PoE+ 的機器：「Tiger Lake-U system features dual 2.5GbE and six PoE+ ports」。

除了 PoE+ 以外另外有 mSATA 與 SATA 支援，然後還有一堆 M.2 的界面可以接 (好像是走 PCIe)：

Lanner’s “IIoT-I530” embedded PC runs Linux on an 11th Gen U-series CPU and supplies with up to 64GB RAM, 2x 2.5GbE, 6x PoE+, 2x COM, 4x USB 3.0, 2x HDMI, 3x M.2, SATA, mSATA, and DIO.

用 USB 供電的 CR2032/CR2016

在「USB board emulates CR2032 or CR2016 coin cell battery」這邊看到的有趣東西，用 USB 供 5V 電進來，然後轉成 3V 透過 CR2032 或是 CR2016 的鈕扣電池形式提供電源：

看說明是可以拿來開發測試用：

You can now develop CR2032 or CR2016 powered devices without having to use an actual coin cell thanks to Peter Misenko’s (Bobricius) “coin cell battery emulator CR2016/CR2032”.

看起來只要旁邊的延伸段不要卡住就可以這樣玩，不過一般開發測試板應該是有 pin 腳可以灌 3V 進去啦，算是蠻有趣的東西就是了...

USB Type-C 要增加 240W 的規格...

在「USB Type-C Specification 2.1 allows up to 240W Extended Power Range (EPR)」這邊看到這個規格：

Extended Power Range cables have additional requirements to assure that these cables can deliver the full defined voltage and current range for USB PD EPR operation. EPR cables shall functionally support a reported 50 V and 5 A o peration. The minimum functional voltage that a cable shall support is 53.65 V. The electrical components potentially in the path of V BUS in an EPR cable, e.g. bypass capacitors, should be minimally rated for 63 V.

All EPR cables shall be Electronically Marked and include EPR-specific information in the eMarker as defined by the USB PD specification. As defined in the USB PD specification, EPR cables are marked as 50 V and 5 A capable. All EPR cables shall be visibly identified with EPR cable identification icons as defined by the USB-IF. This is required so that end users will be able to confirm visually that the cable supports up to as high of PDP = 240W as defined in the USB PD specification.

也是基於 E-Marker 晶片的關係，除了充電頭支援外，線本身也得支援。這解決了目前很多家桌機都自己搞 >100W 的 dock 來支援高瓦數的充電，推出一個標準來涵蓋收斂...

會不會搞到以後連桌機都可以用 USB-C 界面供電啊...

PinePower 120W 充電器

在「PinePower 120W desktop power supply features display, USB PD, QC 3.0 and wireless charging」這邊看到 PinePower 120W 這個充電器：

提供了一個 Type-A QC 3.0 (18W) + 三個 Type-A 5V/3A (15W) + 一個 Type-C PD (65W)，然後還有一個 Qi (10W)，算了一下這些組合全部都跑滿要 138W，然後機器的上限提供 120W，這個集縮比超低，看起來也是頗猛的...

目前 out of stock，剛好可以等其他用過的人的評價...

Apple M1 的效能與省電原因

在 Hacker News Daily 上看到 Apple M1 為什麼這麼快又省電的解釋，可以當作一種看法：

可以在 Thread reader 上面讀：「Thread by @ErrataRob on Thread Reader App – Thread Reader App」。

看起來 Apple 在規劃的時候就有考慮 x86 模擬問題，所以在記憶體架構上直接實做了對應的模式，大幅降低了當年 Microsoft 在 Surface 上遇到的問題：

3/ The biggest hurdle was "memory-ordering", the order in which two CPUs see modifications in memory by each other. It's the biggest problem affecting Microsoft's emulation of x86 on their Arm-based "Surface" laptops.

4/ So Apple simply cheated. They added Intel's memory-ordering to their CPU. When running translated x86 code, they switch the mode of the CPU to conform to Intel's memory ordering.

另外一個比較有趣的架構是，Apple M1 上面的兩個 core 有不同的架構，一顆對效能最佳化，另外一顆對效率最佳化：

13/ Apple's strategy is to use two processors: one designed to run fast above 3 GHz, and the other to run slow below 2 GHz. Apple calls this their "performance" and "efficiency" processors. Each optimized to be their best at their goal.

在 wikipedia 上的介紹也有提到這兩個 core 的不同，像是 L1 cache 的差異 (128KB 與 192KB)，以及功耗的差異：

The M1 has four high-performance "Firestorm" and four energy-efficient "Icestorm" cores, providing a configuration similar to ARM big.LITTLE and Intel's Lakefield processors. This combination allows power-use optimizations not possible with Apple–Intel architecture devices. Apple claims the energy-efficient cores use one tenth the power of the high-performance ones. The high-performance cores have 192 KB of instruction cache and 128 KB of data cache and share a 12 MB L2 cache; the energy-efficient cores have a 128 KB instruction cache, 64 KB data cache, and a shared 4 MB L2 cache. The Icestorm "E cluster" has a frequency of 0.6–2.064 GHz and a maximum power consumption of 1.3 W. The Firestorm "P cluster" has a frequency of 0.6–3.204 GHz and a maximum power consumption of 13.8 W.

再加上其他架構上的改善 (像是針對 JavaScript 的指令集、L1 的提昇，以及用 TSMC 最新製程)，累積起來就變成把 Intel 版本壓在地上磨蹭的結果了...

IBM 把 OpenPOWER Foundation 交給 The Linux Foundation

標題雖然是「Big Blue Open Sources Power Chip Instruction Set」，但實質上應該就是 IBM 把 OpenPOWER Foundation 交給 The Linux Foundation。

找了一下兩邊的新聞稿，其中 The Linux Foundation 的新聞稿在「The Linux Foundation Announces New Open Hardware Technologies and Collaboration」這邊，但 OpenPOWER 的網站好像從 2018 年年底就沒更新了...

開放硬體最近比較紅的應該是 RISC-V 與 OpenRISC 這些專案？IBM 這一招不知道是怎麼樣...

Raspberry Pi 4 的 Type C 無法使用 Macbook Charger 供電的問題

Raspberry Pi 4 出來後有些災情 (畢竟又加了不少東西近去)，在 Hacker News 上看到的 Type C 介面的充電問題：「Raspberry Pi 4 not working with some chargers (scorpia.co.uk)」，引用的原文可以在「Pi4 not working with some chargers (or why you need two cc resistors)」這邊看到，裡面提到了新的 Type C 供電介面在接某些充電器時不會供電 (包括了 Macbook 的充電器)：

The new pi has been released and it has a USB Type-C connector for power however people are finding some chargers are not working with it (notably macbook chargers). Some have speculated that this is due to a manufacturer limitation on the power supplies however it is actually due to the incorrect detection circuitry on the Pi end of the USB connection.

這樣說有點偏頗，但是 Macbook 的充電器一向是 Type C 裡的指標，如果這顆充電器跟其他裝置配合上有問題，通常都是代表其他裝置的實作有問題... (噗)

這次發現的電阻問題看起來有點苦 (看起來需要改版子)，目前文章作者建議的 workaround 主要就是「不要用那麼好的設備」，比較簡單的包括了 Type C 的線不要那麼好 (像是找充手機用的線就好，不要找拿可以跑 5A 的線)，或是透過 Type A 轉 Type C 的線也應該可以避開這個問題，最差的情況應該是找其他的充電器：

Now onto some solutions. Assuming the issue you are having is caused by the problem discussed above, using a non e-marked cable (most USB-C phone charger cables are likely this type) rather than an e-marked cable (many laptop charger/thunderbolt cables and any 5A capable cable will be in this category) will allow for the pi to be powered. In addition using older chargers with A-C cables or micro B to C adaptors will also work if they provide enough power as these don’t require CC detection to provide power. Ultimately though the best solution in the long run will be for there to be a board revision for the pi 4 which adds the 2nd CC resistor and fixes the problem.

對於已經入手的人，如果真的中獎，workaround cost 應該還在可以控制的範圍...

Raspberry Pi 4 開賣，USD$35

Raspberry Pi 4 開賣，目前推出的是 Model B，最低規格的 1GB RAM 版本與之前 RPi 3 相同都是 USD$35，另外這次提供了以前沒有的 2GB 與 4GB 版本，分別是 USD$45 與 USD$55：「Raspberry Pi 4 on sale now from $35」。

有兩個比較大而且要注意的改變，第一個是電源接頭變成 Type-C 了：

We’ve moved from USB micro-B to USB-C for our power connector. This supports an extra 500mA of current, ensuring we have a full 1.2A for downstream USB devices, even under heavy CPU load.

另外一個是 HDMI 接頭換成 D Type：

To accommodate dual display output within the existing board footprint, we’ve replaced the type-A (full-size) HDMI connector with a pair of type-D (micro) HDMI connectors.

這兩個改變都需要準備額外的設備或是線材，其他的改變應該還好...

這次改版最明顯的是效能的增加，官方宣稱 CPU 速度是前一代的三倍：

A 1.5GHz quad-core 64-bit ARM Cortex-A72 CPU (~3× performance)

而在 GPU 相關的則是對 H.265 的 4Kp60 硬體解壓縮：

4Kp60 hardware decode of HEVC video

先前用 RPi 3 放客廳還是覺得不太夠，也許可以考慮看看這個...