List of iPod classics

There are seven major iterations of the iPod classic, formerly referred to as simply iPod.

iPod with scroll wheel (1st generation)
The iPod (1st generation) was released on 2001. A 10 GB variant was introduced on 2002. The 5 GB Rev A variant was sold alongside the iPod (2nd generation) branded as "iPod with scroll wheel", and was released in Mac and Windows variants, formatted for HFS+ and FAT32 respectively, with no cross-compatibility. As iTunes was not yet released for Windows, Apple instead provided Musicmatch Jukebox for Windows users.

General:
 * Release Date:
 * Initial: 2001
 * Rev A: 2002
 * Color:
 * White
 * Madonna, Tony Hawk, No Doubt, and Beck Limited Editions, released 2002

Hardware:
 * Battery: 1200 mAh
 * CPU Specs:
 * Processor: PortalPlayer PP5002
 * CPU Speed: 90 MHz x2
 * RAM: 32 MiB DRAM
 * Storage: 5/10 GB 1.8″ hard drive
 * Connectivity:
 * 3.5mm headphones (stereo)
 * FireWire port
 * Interface:
 * 160×128 2″ monochrome display
 * Mechanical scroll wheel with surrounding navigation buttons

Identifiers:
 * Codename: P68
 * Firmware identifier: 1
 * Gestalt identifiers:,  ,

iPod with touch wheel (2nd generation)
The iPod (2nd generation) is a minor revision, replacing the mechanical wheel with a touch-sensitive one. Its external appearance is identical to its predecessor. It was branded as "iPod with touch wheel".

General:
 * Release Date: 2002
 * Color:
 * White
 * Madonna, Tony Hawk, No Doubt, and Beck Limited Editions, released 2002

Hardware:
 * Battery: 1200 mAh
 * CPU Specs:
 * Processor: PortalPlayer PP5002
 * CPU Speed: 90 MHz x2
 * RAM: 32 MiB DRAM
 * Storage: 10/20 GB 1.8″ hard drive
 * Connectivity:
 * 3.5mm headphones (stereo)
 * FireWire port
 * Interface:
 * 160×128 2″ monochrome display
 * Touch-sensitive wheel with surrounding navigation buttons

Identifiers:
 * Codename: P68
 * Firmware identifier: 1
 * Gestalt identifiers: ,
 * USB product identifier:

iPod with dock connector (3rd generation)
The iPod (3rd generation) is the first Apple device to make use of the 30-pin Connector, replacing the built-in FireWire port. The 30-pin dock connector is capable of charging and syncing with a computer via FireWire, additionally adding support for syncing with a computer (but not charging) via USB. Musicmatch Jukebox continued to be supplied as Apple's Windows solution, until iTunes was later released for Windows. There are no longer Mac and Windows-specific variants - an iPod will be formatted to the appropriate filesystem on first sync with iTunes or Musicmatch Jukebox. It was branded as "iPod with dock connector".

General:
 * Release Date:
 * Initial: 2003
 * Rev A: 2003
 * Rev B: 2004
 * Color: White

Hardware:
 * Battery: 850 mAh
 * CPU Specs:
 * Processor: PortalPlayer PP5002
 * CPU Speed: 90 MHz
 * RAM: 32 MiB DRAM
 * Storage:
 * Initial: 10/15/30 GB 1.8″ hard drive
 * Rev A: 10/20/40 GB 1.8″ hard drive
 * Rev B: 15/20/40 GB 1.8″ hard drive
 * Connectivity:
 * 3.5mm headphones (stereo)
 * 30-pin Connector - FireWire (charging and data) and USB (data only)
 * Interface:
 * 160×128 2″ monochrome display
 * Touch-sensitive wheel with touch-sensitive navigation buttons above

Identifiers:
 * Codename: Q14
 * Firmware identifier: 2
 * Gestalt identifiers:
 * USB product identifier:

iPod with Click Wheel (4th generation)
The iPod (4th generation) replaces the device's input interface with the now-iconic click wheel, integrating the device's touch navigation buttons with clickable ones built into the wheel. It was branded as "iPod with Click Wheel".

General:
 * Release Date: 2004
 * Color:
 * White
 * U2 Special Edition (Black/Red), released 2004

Hardware:
 * Battery: 950 mAh
 * CPU Specs:
 * Processor: PortalPlayer PP5020
 * CPU Speed: 80 MHz
 * RAM: 32 MiB DRAM
 * Storage: 20/40 GB 1.8″ hard drive
 * Connectivity:
 * 3.5mm headphones (stereo)
 * 30-pin Connector - FireWire and USB (charging and data)
 * Interface:
 * 160×128 2″ monochrome display
 * Touch-sensitive click wheel with navigation buttons

Identifiers:
 * Codename: Q21
 * Firmware identifiers: 4, 10
 * Gestalt identifiers: ,
 * USB product identifier:

iPod Photo
The iPod Photo is a variant of the iPod (4th generation) with a full-color display, sold as a higher-end model in the product line. With Rev B, it was rebranded as "iPod with color display", replacing the iPod (4th generation) in the product line.

General:
 * Release Date:
 * Initial: 2004
 * Rev A: 2005
 * Rev B: 2005
 * Color:
 * White
 * Harry Potter Special Edition (White), released 2005

Hardware:
 * Battery: 1200 mAh
 * CPU Specs:
 * Processor: PortalPlayer PP5020
 * CPU Speed: 80 MHz
 * RAM: 32 MiB DRAM
 * Storage:
 * Initial: 40/60 GB 1.8″ hard drive
 * Rev A: 30/60 GB 1.8″ hard drive
 * Rev B: 20/60 GB 1.8″ hard drive
 * Connectivity:
 * 3.5mm headphones (stereo)
 * 30-pin Connector - FireWire and USB (charging and data)
 * Interface:
 * 220×176 2″ color display
 * Touch-sensitive click wheel with navigation buttons

Identifiers:
 * Codename: P98
 * Firmware identifiers: 5, 11
 * Gestalt identifiers:
 * iPod Photo:
 * iPod with color display:
 * USB product identifier:

iPod with video (5th generation)
iPod (5th generation), officially branded as "iPod with video", introduced a larger display for video playback. Rev A introduced a brighter display and improved battery life. This revision is frequently referred to as "5.5th generation" or "5th generation enhanced".

General:
 * Release Date:
 * Initial: 2005
 * Rev A: 2006
 * Color:
 * Black/White
 * Harry Potter Special Edition (White)
 * U2 Special Edition (Black/Red), released 2006

Hardware:
 * Battery:
 * 30 GB: 650 mAh Li-ion
 * 60 GB: 850 mAh Li-ion
 * CPU Specs:
 * Processor: PortalPlayer PP5021C
 * CPU Speed: 90 MHz
 * RAM:
 * 30 GB model: 32 MiB DRAM
 * 60/80 GB models: 64 MiB DRAM
 * Storage:
 * Initial: 30/60 GB 1.8″ hard drive
 * Rev A: 30/80 GB 1.8″ hard drive
 * Connectivity:
 * 3.5mm headphones (stereo with composite video output)
 * 30-pin Connector - FireWire (charging only) and USB (charging and data)
 * Interface:
 * 320×240 2.5″ color display
 * Touch-sensitive click wheel with navigation buttons

Identifiers:
 * Codename: M25
 * Firmware identifiers: 13, 20, 25
 * Gestalt identifiers:
 * Initial:
 * Rev A:
 * USB product identifier:

iPod classic (6th generation)
iPod classic (6th generation) changed the front plate design from shiny plastic to aluminium, and was revised three times. Rev C remained on sale until 2014, an unusually long time for Apple. It is speculated that this was to allow the inventory of parts used for iPods to be fully depleted.

Due to the long sale lifespan, and distinct differences between each revision, the revisions have also been colloquially referred to as the following:

Rev C does not seem to have brought major hardware changes. However, it did change the WTF mode identifier.

General:
 * Release Date:
 * Initial: 2007
 * Rev A: 2008
 * Rev B: 2009
 * Rev C: Late 2012
 * Color:
 * Initial: Silver, Black
 * Rev A/Rev B/Rev C: Silver, Gray

Hardware:
 * Battery:
 * Initial 80 GB: 650 mAh
 * Initial 160 GB: 850 mAh
 * Rev A/Rev B/Rev C: 650 mAh
 * CPU Specs:
 * Processor: Samsung S5L8702
 * CPU Speed: ? MHz
 * RAM: 64 MiB DRAM
 * Storage:
 * Initial: 80/160 GB 1.8″ hard drive
 * Rev A: 120 GB 1.8″ hard drive
 * Rev B/Rev C: 160 GB 1.8″ hard drive
 * Connectivity:
 * 3.5mm headphones (stereo - remote control support introduced in Rev A)
 * 30-pin Connector - FireWire (charging only) and USB (charging and data)
 * Interface:
 * 320×240 2.5″ color display
 * Touch-sensitive click wheel with navigation buttons

Identifiers:
 * Codename: N25
 * Firmware identifiers: 24 (Initial), 33 (Rev A), 35 (Rev B), 38 (Rev C)
 * USB product identifiers:
 * Normal mode:
 * DFU mode:
 * WTF mode:  (Initial),   (Rev A),   (Rev B),   (Rev C)