The top/front notification panel of DS1821+ is connected to the motherboard via a ribbon cable. On this board, there are eight micro LEDs (on one side for the HDD activity) and seven LEDs on the other side for the front IO activity.
The motherboard of DS1821+ is extremely clean without any over a fluxed area or over-soldered connections. The top side of the motherboard features a large passive heat sink and a DOM (Disk On Module) board where DiscStation OS lives. On the backside of the motherboard, there are two RAM slots. The Synology DiskStation DS1821+ comes with 4Gb DDR4 2666 RAM by default. There is another available slot if you wish to upgrade RAM in this appliance.
The Daughterboard of DS1821+ to which drives are being attached has eight SAS-type connectors. Even though DS1821+ has SAS-type slots SAS bases drives are not supports in this enclosure. On the board itself there is one Microchip PIC16F19197 that regulates power flow to the drive bays.
On the second daughterboard, there are no chips as it acts as a bridge between m.2 and motherboard.
The DDR4 RAM itself in DS1821+ is provided by Samsung K4A4G085WF-BCTD. There are eight chips on this module which are 512 MB each and operate at 2666 Mbps speed.