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Upgrading RAM in Loongson2F-based computers
Starting point
The Lemote Yeeloong currently comes with 1GB of RAM, and the Fuloong 2F comes with 512MB. Numerous reports around the net indicate that the RAM sticks shipped are DDR2-667 modules manufactured by A-Data.
Upgrading
Add or replace?
Since both Yeeloong and Fuloong have only one RAM slot, upgrading RAM means removing the original stick and installing a new one. So choose a stick according to the total size of RAM you need.
Which kind of memory?
SO-DIMM module of no less than DDR2-667 grade, also known as “PC5300”.
DDR2-800 (“PC6400”) is also okay, because these faster modules can also operate at 667 MHz with no issues.
Single-rank only!
Here comes the most important part. According to Lemote, the Yeeloong and Fuloong can accept only single-rank DDR2 modules with sizes up to 2 GB.
“Single-rank” here means that a module must have no more than one row of four chips on each side, 8 in total. Less than 8 is okay, more (i.e. 16) is a no-go.
...but even then
IMPORTANT: there are some reports that even single-rank 2 GB sticks do not work. It is known that the supposedly single-rank “Hynix SKU 022372, GR2GS8T2568-667-HP25 CUS 2GB” does not work in the Yeeloong. Also note that when you order a single-rank MT8HTF25664HZ Micron stick from online vendors (such as Memory4less), they may send you the wrong MT16HTF25664HZ dual-rank one.
And there is a report of the above-mentioned proper single-rank MT8HTF25664HZ not working either.
EMTEC Gdium, on the other hand,
…has been reported to work with just a random 2GB module made by Transcend, marked as '2G DDR2 667 SO-DIMM CL6', part number 221787-4078 and on a separate sticker JM667QSU-2G-E – with 8 chips on each side. Maybe Gdium has a more favorable board layout for high-capacity DDR, despite the memory controller being within the CPU (and in theory same limitations would apply to all hardware based on it).
and even Fuloong,
”…the Lemote Fuloong seems more resilient to the type of RAM it accepts, and jasper@ mentioned he successfully upgraded his device using a Kingston 2GB DDR2 SO-DIMM module (KFJ-FPC218/2G). Unfortunately, this module does not work on any of my Yeeloongs.”1)
KFJ-FPC218/2G appears to be a dual-rank module, so it might be that on the Fuloong (some of?)those actually can work.
1GB or 2GB?
Single-rank 2GB modules seem to be quite rare and difficult to find, and even with a single-rank 2GB module, according to Lemote the stability is not guaranteed. So in practice this means that the maximum amount of RAM for both Fuloong and Yeeloong will be 1GB.
However if you manage to successfully upgrade your Yeeloong or Fuloong to 2 GB of RAM, I'll be very interested to hear about your experience – most importantly, which brand and model of RAM you used.
Testing the new RAM
After installing your new RAM stick, make sure the stability is not compromised. Unforunately the well-known “Memtest86+” does not exist for MIPS, but you can use the memtester package, first closing all the memory-hungry apps including X.org (so that almost all RAM is free), then running memtester with a value close to the total amount of RAM (leave about 50 MB for the OS).
