# Hardware Topology This document describes when each type of hardware feature needs a new topology value. [TOC] ## Screen Changes that require new topology * Size change: e.g. 15” vs 12” * Native screen resolution changes * Technology change: e.g TFT vs IPS vs OLED * Touch change: e.g. no touch vs touch * Rounded corners Changes that do not require new topology * Vendor supplier change with all same above functionality ## Form Factor Changes that require new topology * Clamshell/Convertible/Detachable/Tablet/Chromebox/Chromebase Changes that do not require new topology * Changing color of plastics and other cosmetic modifications * Changing hinge location (assuming convertible type remains the same) ## Audio Changes that require new topology * Same amplifier chip, but different number of speakers * Same amplifier chip, same number of speakers, but different placement of speakers. * Different number of microphones or different placement of microphones (A/B/C/D panels) Changes that do not require new topology * Different placement of same audio codec on MLB ## Stylus Changes that require new topology * Presence of stylus support (even if device doesn’t ship with stylus) * Garage type of stylus: e.g. garaged internally vs stored externally * Wake-on-eject hardware support: e.g. supported vs not supported * Technology type: e.g. USI vs EMR Changes that do not require new topology * Where external stylus position is on device ## Keyboard Changes that require new topology * Presence of internal keyboard * Any key presence change: e.g. power button present, lock button present, number pad presence or not. * Presence of backlight Changes that do not require new topology * Moving keys around (e.g. moving Delete key to a different location). * Assuming no EC driver support is needed for this change. If EC driver support is needed, then that would require a new topology value * Changing Z height of keys or travel for each key press ## Thermal Changes that may require a new topology * More powerful SoC * Presence of fan * Any changes in a device that may require different thermal tuning and consideration ## Camera Changes that require new topology * Different A/B/C/D panel placement of cameras. e.g. 1A-1B vs 1B-1D * Also implies difference in total camera count for system * If camera supports ARcore in hardware * Different resolution for camera Changes that do not require new topology * Different vendor for camera * Different OS driver required for camera ## Accelerometer/Gyroscope/Magnetometer/Proximity/LightSensor {#sensor} Changes that require new topology * Different lid/base placement. e.g. 2lid-1base vs 1lid-2base * Number of sensors present on system * HW that requires a different EC driver Changes that do not require new topology * Moving sensor sub-board placement within the lid (if it moves out of the lid, then we a new topology is required) ## Fingerprint Sensor Changes that require new topology * Number of fingerprint sensors * HW interface change Changes that do not require new topology * Placement of sensor on the device (e.g. left side or right side) ## Daughter Board Changes that require new topology * Using a different daughter board Changes that do not require new topology * The length of the cable connecting the MLB and the DB ## Non-Volatile Storage Changes that require new topology * Technology change: e.g. eMMC vs NVMe * Component change that requires different FW tuning parameters Changes that do not require new topology * Size of storage: e.g. 32GB vs 128GB ## RAM Deprecated. This is no longer encoded in the design. ## WIFI Changes that require new topology * Change in bus: e.g. CNVi vs PCIe Changes that do not require new topology * Different vendor/part on same bus ## Bluetooth Changes that require new topology * Changes in component (vendor_id, product_id, bcd_device) Changes that do not require new topology * None currently ## BarrelJack Changes that require new topology * Present or absent of barrel jack Changes that do not require new topology * Placement, voltage ## Cellular Board Changes that require new topology * Presence of Cellular board Changes that do not require new topology * Second sourced component changes that do not affect FW ## SD Board Changes that require new topology * Presence of SD reader board Changes that do not require new topology * Second sourced component changes that do not affect FW ## Motherboard USB Changes that require new topology * Swapping out USB ICs like TCPCs, PPCs, SSMUXs, or retimers Changes that do not require new topology * Adding/Removing isolation diodes on USB lines ## Power Button Changes that require new topology * Region of device (i.e. is the button on the screen, keyboard, etc.) * Edge of device (i.e. is the button on the left side of the screen) * Relative position of button on edge (i.e. how far up the left side of the screen is the button) Changes that do not require new topology * Second sourced component changes ## EmbeddedController Changes that require new topology * New EmbeddedController type, such as Chrome EC, Wilco EC * New EC part number, such as npcx5m6g Changes that do not require new topology * EC capabilities, such as usbpd or keyboard ## Touch Changes that require new topology * Needs switching the different feature like numpad in the fw Changes that do not require new topology * Different touch controller vendor which supports the same feature set ## Trusted Platform Module Changes that require new topology * New type, such as "third party" or GSC "Google Security Chip." Changes that do not require new topology * New RO firmware. ## Microphone mute switch Changes that require new topology * Microphone mute switch presence ## HDMI Changes that require new topology * HDMI port ## HPS Changes that require new topology * Presence of HPS board ## DP Converter Changes that require new topology * Addition, removal, or change of DisplayPort converter devices Changes that do not require new topology * New firmware for DisplayPort converters ## PoE Peripheral support Changes that require new topology * Presence of hardware for PoE peripheral support ## Power supply Changes that require new topology * Presence or absence of barrel jack * Preferred input power ## Battery Changes that require new topology * Supports booting with no battery ## dGPU Changes that require new topology * Supports discrete GPU ## UWB Changes that require new topology * Supports UWB (Ultra Wideband) ## Detachable Base Changes that require new topology * Presence of the detachable base ## SoC Changes that require new topology * Differences in SoC SKU requiring software or firmware differences ## Fan Changes that require new topology * Supports number of fan