Electronic Design

10 Key Facts About The Standards

  1. Reduced cost: The riser-card standards migrate hardware functionality from add-in cards to the motherboard, either as control functions added to the PC's core logic or as software drivers running on the host CPU. Depopulated cards (risers) cost less; require a simpler, less-expensive serial interface; and eliminate redundant parts (such as PCI control) that would previously have been present in each add-in card.
  2. Faster time-to-market: Motherboards can be certified separately from riser cards, which streamlines the motherboard certification process.
  3. Easier integration: All PC subsystems can be controlled by a single Super Southbridge chip set, rather than by separate controllers. Riser cards can support multiple connectivity options, such as modem, DSL, and HPNA, on a single card
  4. Easier upgrade: Functions that can be implemented in software on the CPU, such as data compression/decompression, can be upgraded over the Internet. This eliminates the need for hardware replacement.
  5. RJ-11 convergence: Instead of needing one jack for HPNA and another for a modem, ACR and CNR offer the flexibility of interfacing both functions via a single connector. ACR extends this to include DSL.
  6. Build-to-order flexibility: OEMs can serve several SKUs—for example, an entry-level PC, a business PC, and a gaming unit—with one motherboard by adding the appropriate riser.
  7. Greater reliability: Consolidating functions in the Super Southbridge chip set, rather than implementing them as multiple controllers scattered around the unit, reduces the number of parts that can fail. Reliability also is enhanced because of the greater physical separation between noise-sensitive communications systems from the noisy environment of the motherboard.
  8. More marketing power: OEMs can mix and match functions on a riser card, creating combinations tailored to specific PC market segments.
  9. Conserve PCI slots: As computers get smaller and the demand for add-in functions gets larger, riser cards can provide multiple communications functions without consuming multiple PCI slots.
  10. Smaller form factors: Both ACR and CNR specifications recommend riser-card-based solutions that take up less space than the PCI add-in cards they replace.
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