https://stackoverflow.com/questions/...imer-frequency
引用:
When configuring your kernel you can choose a timer frequency of either 100Hz, 250Hz, 300Hz or 1000Hz. All of these are supported, and although 1000Hz is the default it's not always the best.
People will generally choose a high value when they value latency (a desktop or a webserver) and a low value when they value throughput (HPC).
Player 那邊是把整個 piCorePlayer 放進 DDR4 RAM,因此 CF/SD/micro SD 卡的 latency 並不重要,反正成功開機後的 latency 都是 DDR4 RAM 的級數。
https://docs.picoreplayer.org/components/lms/
引用:
Logitech Media Server (LMS) is a server database application and needs to be shutdown properly
但 LMS 必須(因此不要胡亂關機)把一些檔案放到 CF/SD/micro SD 卡,那麼問題來了,176.4KHz 核心頻率的 latency 相當低,但是 latency 比較高的 CF/SD/micro SD 卡就成為整個系統的瓶頸,結果是比較高的核心頻率還有可能會弄巧反拙。
CF 的介面實屬 IDE/ATA 那個年代,但 CFexpress 則是 PCIe 的說:
https://www.stsd99.com/phpBB3/viewto...p=20246#p20246
引用:
因為最近發現,我的環境撥放採樣48khz倍數會停掉,需要重開機的情況經過更換成cfexpress記憶卡+ cfexpress讀卡機,居然不會發生了,很正常的聽了幾天沒問題
引用:
補充下cfexpress記憶卡+ cfexpress讀卡機,跟CF卡聽感上的差異
開聲不用很注意聽,光是三頻量感就超出CF卡非常多,但是細節並未被暴增的能量掩蓋,簡單說就是更為厚實了,尤其是低頻下淺深到令我以為8吋單體變成12吋了
但是這是否代表更好就需要看環境了,因為我的聆聽環境不大,增加的能量讓我覺得太過了,同樣音量下不適合長時間聆聽
還是CF卡出來的聲音適合我的小空間,而且也比cfexpress卡便宜好多好多...
品牌的讀卡機並不便宜,大約是 ¥260 左右:
https://item.taobao.com/item.htm?id=624804106826
最便宜的品牌 64GB CFexpress Type B 卡亦高達 ¥750:
https://item.taobao.com/item.htm?id=657340952419
通常香港的售價是更加便宜一點點,目前是(880 - 20)= $860/大約 ¥710:
https://www.price.com.hk/product.php?p=441830
讀卡機就是 $280/大約 ¥230:
https://www.price.com.hk/product.php?p=447072
其他不知名的『雜牌』產品就算了,倒不如用 M.2 2230 尺寸的 NVMe SSDs 自製一些無需打磨 PCB 的 CFexpress 卡:
https://item.taobao.com/item.htm?id=657694302445
原裝拆機的 128GB 只需 ¥128,讀寫速度方面也沒有甚麼關係,畢竟 Gen1 的 USB 3 就只有 5Gbps,極其量只有 600MB/s:
https://item.taobao.com/item.htm?id=597937979631
但重點是既然 CFexpress 讀卡機也能夠正常開機,乾脆用『正常』尺寸的 NVMe SSDs 加上一般的 USB 外接盒也並不一定是沒有希望。
CFexpress 卡(PCIe 介面)的 latency 肯定比 CF 卡(IDE/ATA 介面)優秀,或許 latency 就是致勝的關鍵,只要選擇 latency 方面比較理想的 SSDs 就能夠解決瓶頸的問題,畢竟最終目標就是發掘核心頻率的潛力:
https://i.imgur.com/cjmnYzn.jpg
https://i.imgur.com/SGmZ9c3.png
https://i.imgur.com/u0gpL2G.jpg
承接最近關於『沒有比較就沒有傷害』方面的討論,其實也沒有必要作出多餘的比較,一般 NAND Flash 記憶體的 latency 也是洗洗睡的模樣,Intel Optane 的 3D XPoint 輕易擊倒同一時期的大部分對手:
https://www.anandtech.com/show/12136...480gb-review/2
https://i.imgur.com/ehaKMbm.png
https://i.imgur.com/yrt6PK2.png
https://i.imgur.com/GMEgK7s.png
https://i.imgur.com/6Srhv5S.png
https://www.anandtech.com/show/12136...480gb-review/3
https://i.imgur.com/4VFak8t.png
https://i.imgur.com/kUCCSpF.png
https://i.imgur.com/6it58lP.png
https://i.imgur.com/ZTazXVz.png
https://www.anandtech.com/show/12748...ng-refreshed/4
https://i.imgur.com/Y3pJcS9.png
https://i.imgur.com/DT1cFQ2.png
https://i.imgur.com/B1cQtLi.png
https://i.imgur.com/sqjX8pE.png
https://www.anandtech.com/show/12748...ng-refreshed/5
https://i.imgur.com/Adg37KD.png
https://i.imgur.com/lASYiyB.png
https://i.imgur.com/24EHnFP.png
https://i.imgur.com/QEAMRic.png
https://www.anandtech.com/show/12748...ng-refreshed/8
https://i.imgur.com/lcYB64k.png
https://i.imgur.com/oYddxrA.png
https://www.anandtech.com/show/13704...ung-memblaze/5
https://i.imgur.com/90CSfL2.png
https://www.anandtech.com/show/13704...ung-memblaze/6
https://i.imgur.com/hMNuYf3.png
https://audiophilestyle.com/forums/t...omment-1088701
引用:
The P4800X sounds better than the 900P! And the PCIe version sounds better than the M.2 version (P4801X).
當然那些只是跑分方面的理論,幸好實際使用後的結論仍然是 Optane 900P 力壓群雄:
https://www.ptt.cc/bbs/Headphone/M.1...047.A.7E7.html
引用:
這顆SSD當初跟900p比較過,都吃主板電源下,900p在性能動態上還是比較優異,可以試試看。另外Bios參數也可以tune一下很有感,調整完打電動目前沒感覺有影響到
引用:
以前印象都是不管用啥M.2都被900P海電,這如果顆能比肩就很強了
超強的 Taiko Audio SGM Extreme 也是 Optane 900P,毫不留情地戰勝了 CF 卡的 latency:
https://audiophilestyle.com/ca/revie...t-2-of-5-r908/
引用:
Aside from the illuminated power switch on the front panel, all the goodies are accessible on the back: A USB 3.1 Gen 2 socket to your DAC, multiple USB 3.1 Gen 1 sockets and LAN ports for data, a StarTech PEX1000SFP2 PCIe optical Network card, a 280GB Intel Optane 900P storage drive for the operating system
https://www.hiendy.com/?p=11367
引用:
SGM Extreme Server的架構有別於市場上其他音樂伺服器。它的每一枚CPU,分別連接12組4GB記憶體,代表SGM Extreme Server兩組CPU架構下各自擁有 ECC 48GB記憶體。這些記憶體全數為Taiko audio 特別自製 low profile, 用以減低 micro vibration , h而且每粒晶片皆經過人手嚴格配對, matched components , 所以以最低 low latency 運行,
https://www.monoandstereo.com/2020/0...xperience.html
引用:
One of the advantages of being so heavily entrenched in DIY is that over time, you get a real sense of the SQ contribution of individual components. Over the years, I have tested various SSDs (SATA II vs SATA III, SLC vs MLC), storage transmission buses (SATA vs PCIe) and even SATA cables and have found that they each have a particular sonic signature that is audible. The fastest SSDs have the lowest latencies but also generate a high frequency noise that I find fatiguing with long term listening and cannot be completely ameliorated with SATA filters or by cleanly powering the SSD. Just because you power an SSD with a high quality linear power supply doesn't prevent that SSD from generating high frequency noise. This is apparently not noticeable by all given how commonly SSDs are used in music servers today but I have purposely avoided using an SSD as an OS drive (which is incessantly being accessed by the OS even during music playback) in any of my builds since late 2018. I have even gone so far as to use a compact flash as an OS drive but as these are very high latency storage devices, they create as many problems as they fix and proved to be a less than ideal solution. In late 2018, through the reporting of others, I began using Optane drives for the operating system and these drives have proven to be the ideal solution. Optane drives have very low "RAM like" latencies but also have a noise spectrum that is more like RAM than an SSD which is to say they do not cause the same fatiguing HF noise. It was quite refreshing to find that the Extreme uses an Optane drive for its OS.
初代 16GB Optane 的淘寶價格為 ¥20 起,假如 USB 外接盒的實驗成功開機後可以試試升級 25MHz 的 TCXO 或者 OCXO 時鐘,最後根據自己的需求與預算考慮是否升級到 280GB 或以上的 Optane 900P,詳情則毋須重複了,Optane 無法開機的話就試試 BerryBoot v2.0 吧:
https://www.my-hiend.com/vbb/showthr...493#post244493
800 鎂的那個 Revelation Audio SSD 只是 Crystek CCHD-957,故此利用樹莓派 OCXO 時鐘板的那一對 25MHz 輸出就能夠同時升級 Optane 與及 USB 外接盒兩者的時鐘,或許最後的結果是相對便宜的 Optane 900P 並不遜於 Revelation Audio?
另外如果需要大量購入 Morion MV85 10MHz OCXO 的話可以考慮是否用 ¥800 買 10 顆庫存新貨,畢竟 Ustars Audio 的那一位淘寶賣家已清楚說明他的 MV85 非全新,那麼另一位賣家的 MV85 確實是庫存新貨的話也不錯:
https://item.taobao.com/item.htm?id=552098420070
但小弟還是不明白舊貨與新貨 OCXO 兩者之間的分別:
https://audiophilestyle.com/forums/t...comment-874851
引用:
The age-related frequency drift typically follows an asymptotic curve, meaning that it gets smaller over time. So as the crystal gets older, the rate of frequency change get lower and lower. After just a few years, the rate of change is then typically lower than the original spec for the fresh oscillator.