Seven component classes, one page. Each section: what it is, how specs are read, the common misconception, and the used-buying risk to check.
Knowledge pages are educational references, independent of sales inventory. Items without confirmed sourcing are reference-spec — quoted on demand.
Server DDR4/DDR5 comes in registered (RDIMM), load-reduced (LRDIMM) and unbuffered (UDIMM) forms. Servers overwhelmingly use RDIMM; LRDIMM only for maximum-capacity builds; UDIMM belongs to desktops and some entry towers. Misconception: "faster is always better" — modules clock to the platform. Used-buying check: per-module test results and SN list; reject unlabelled mixed lots.
Intel Xeon Scalable generations (1st–5th) and AMD EPYC (Naples through Genoa) define the whole platform: socket, memory speed, PCIe generation. Misconception: core count alone determines value — per-core clocks and licensing often matter more. Used check: matching steppings in dual-socket systems; no bent socket pins.
SAS and SATA drives dominate legacy bays; NVMe rides PCIe for an order-of-magnitude latency drop. Misconception: capacity per dollar is the whole story — endurance (DWPD) and interface generation gate real value. Used check: SMART/wear data mandatory; this section is a selection and compatibility reference; specific supply is confirmed by quotation.
RAID controllers (Dell PERC, HPE Smart Array) build redundant arrays with cache; HBAs pass drives straight through — the mode software-defined storage wants. Misconception: RAID always protects — a dead cache battery silently degrades write behavior. Used check: controller model, cache module and battery/capacitor health.
Data-center accelerators occupy double-width PCIe slots with heavy power draw; server support depends on risers, power kits and airflow, not just the slot. Misconception: any 2U "supports GPUs" — configurations differ per unit. Note: this section is a platform-capability reference; specific supply is confirmed by quotation.
10/25/100GbE adapters (Intel, ConnectX families) plus OCP/NDC mezzanine formats. Misconception: a port is a port — offload features and firmware levels change real throughput. Used check: exact model revision and transceiver compatibility.
Dual hot-plug PSUs sized to configuration; fans are consumables in used units. Misconception: max-wattage PSU is always better — efficiency curves matter at real loads. Used check: PSU part numbers match, fan hours/noise, no thermal-event history in BMC logs.