Just recently I've bought myself a cool gadget for my Philips VG-8235 MSX2 computer.
It's an SD512 cartridge by 8bits4ever (http://www.8bits4ever.net/product-page/098e6224-da0c-4b83-ab5f-3cac906cd249), I ordered it
from ebay (but also from the manufacturer), as it was out of stock in the online shop at the time. The cost was 81,5 euro with shipping, and 4GB micro SD filled with MSX goodies.
I've received the card around a week after my order, it came in a solid, well protected package, and I was sent all the necessary instructions and OS files via e-mail earlier. The card itself is manufactured really nicely, the one I have is in a blue transparent case, with a blue led blinkin' while accesing the card.
SD512 has two independent slots, one for micro SD, one for standard SD card. It also comes equipped with 512 kb Ram, which can be configured by switches to either Mega Ram, Mapper, or turned off. I use it most in mapper mode, with purpose of mounting *.ROM images.
On the attached micro SD I found Nextor 2.10 software, along with latest SofRun installed, and some *.ROM and *.DSK files with games for my tests. For those, who don't know Nextor is an operating system compatible with MSX-DOS with native support for Fat16, and SofaRun is a great software pack, aimed at easy running of games from *.ROM and *.DSK files.
While I'm still an inexperienced MSX user, I've found that not all of the games I have run straight off SD512. With ROM files it's really a gamble, most of the smaller, MSX1 roms work, but I have problems running a lot of MSX2 ROMS. Around half of the 256 kb ROMS work, and I haven't been able to run any of the 512 kb roms, even though SD 512 has the necessary memory. Same applies to DSK software, and that's because some of the non standard disks work only from a real floppy, or using a floppy emulator like HXC. On the other hand, all of the standard files based software, including all the recent MSX1&2 scene demos works great.
Short list of some of the ROM's that run flawlessly:
Maze of Galious
Overall I must say that SD512 is a great piece of hardware. The thing with some ROM's not running is due to the fact, that I'm a lamer when it comes to MSX, and I still haven't investigated software like execrom.com and romload.com correctly, I still need to mess some more with the options. And another tihng is that this sowtware is in fact a hack, and ROM files should be flashed using proper Flash ROM cartridges, and no be mounted in RAM, and that is completly different hardware than SD512.
The baseline is: SD512 is a nice hardware, doing it's job as a mass storage device and RAM expansion.
p.s. You can also check a cool article about MSX ram expansions here: http://www.lavandeira.net/2016/07/multi-review-msx-memory-mapper-mega-mapper-and-memory-samurai-part-1-of-2/
http://msx.org - ultimate msx resource
http://www.8bits4ever.net - hardware producer
http://lhalter.free.fr/mgr/ - SofaRun and other great soft form MSX