I've added memory modules to QNAP TS-253D(https://www.qnap.com/ja-jp/product/ts-253d). The specification(https://www.qnap.com/ja-jp/product/ts-253d/specs/hardware)says:
Max memory: 8 GB (2 x 4GB)
And CPU(Intel Celeron J4125) specification (https://www.intel.co.jp/content/www/jp/ja/products/sku/197305/intel-celeron-processor-j4125-4m-cache-up-to-2-70-ghz/specifications.html) says:
Max Memory size(depending on a memory specification): 8 GB
But, results of search engines says that max memoy is 32GB.
QNAP X53D 16GB And 32GB Crucial Memory Upgrade Guide
At first, I attached 8GB SO-DIMM × 2, this was ok. Then, I've tried to attach 16GB SO-DIMM × 2, this was no ok. Above blog says:
VERY IMPORTANT – The Links used in the article below towards the correct unofficial memory are occasionally changed (beyond my control) as it will direct you to the site in your own region/country. MAKE SURE to check that the memory module (especially 16 and 32GB SODIMM modules) are DUAL RANK or ‘DR‘, as Synology NAS typically have trouble with SR/SINGLE RANK modules.
I should use DUAL RANK memories(the memory modules that I used were 2GB×8 SINGLE RANK. I've bought new DUAL RANK memories as following:
Timetec Hynix IC ノートPC用メモリ 32GB(2x16GB) DDR4 2666MHz PC4-21300 Dual Rank 260 Pin SODIMM 32GB(2x16GB)and tried to attach them. Boot time is longer than usual, probably it takes 1 or 2 mins later, finaly booted. Then I've checked the system status of QNAP, this screen says 32GB memory was attached.