ARRIS CM820A DOCSIS 3.0 8x4 Cable Modem

The ARRIS CM820A is a DOCSIS 3.0 8x4 cable modem built to deliver fast, reliable internet for homes and small businesses with simple one-step activation.

The CM820A combines ARRIS engineering and DOCSIS 3.0 channel bonding to provide broadband speeds suited for streaming, gaming, remote work, and small-office tasks. Its 8x4 downstream/upstream configuration, MoCA immunity filter, and dual 96MHz RF tuners let the modem handle multiple high-bandwidth activities while meeting industry immunity and surge standards. This modem is intended for use with compatible cable internet service plans — check with your ISP before purchasing.

How fast can the CM820A realistically perform on typical cable plans?

The CM820A uses 8 downstream and 4 upstream bonded channels to aggregate throughput. While top speeds depend on your ISP plan and network conditions, this modem supports data rates that allow many plans above 300 Mbps when the provider supplies that capacity.

• 8x4 channel bonding to combine multiple RF channels for higher throughput
• Two independent 96MHz RF tuners to capture downstream channels up to 1 GHz
• Designed to support multi-device home or small-office usage

What connectivity and protection features does the CM820A include?

The CM820A includes a built-in MoCA immunity filter and meets common radiated immunity and surge requirements, helping reduce interference and protect connected devices. The modem’s RF design and standards compliance are intended to improve stability on properly provisioned cable networks.

• Integrated MoCA immunity filter to minimize home-network interference
• Compliance with industry radiated immunity and surge specifications
• Flexible NxM channel bonding for downstream/upstream adaptability

How easy is setup and activation with my internet provider?

The CM820A supports one-step activation with many cable operators, simplifying the onboarding process compared with older modems. Activation requirements vary by ISP, so confirm compatibility and any plan prerequisites before attempting to connect.

• Designed for quick, single-step activation processes with many providers
• Check with your ISP to ensure the modem is supported on your service
• Works as a dedicated cable modem — pair with a separate router for Wi‑Fi

What setup or equipment considerations should I know before buying?

The CM820A is a cable modem only and does not provide Wi‑Fi; pair it with a router if wireless is needed. Verify your ISP supports DOCSIS 3.0 8x4 modems and whether they allow customer-owned modems on your plan to avoid unexpected activation issues or rental fees.

• Modem-only device — add a router for wireless networking
• Confirm ISP compatibility and supported speed tiers prior to purchase
• Supports commercial and residential installations on compatible networks

Who is this for: The ARRIS CM820A is aimed at households or small businesses that need dependable wired broadband with higher aggregated throughput than single-channel modems offer. It fits users who want to avoid monthly rental fees by owning their modem, have a DOCSIS 3.0-compatible cable plan (often above basic speeds), and can pair the unit with a separate router if Wi‑Fi is required. For heavy multi-device Wi‑Fi users or those seeking the newest DOCSIS 3.1 features, consider a gateway or DOCSIS 3.1 model instead; for many users on mid-to-high-tier cable plans, the CM820A provides a stable, cost-effective wired connection backed by ARRIS reliability.