ThinkPad S30 and S31
Japan-only Pentium III model with no CD drive, a 10 inch screen, 256MB Maximum RAM, PCMCIA slot, CF slot, 2 USB 1.1 ports, Firewire port, RJ11 and RJ45, and a keyboard with English and Japanese shared keys. Battery with built-in stand, long life 5 hr run. HDD 20 GB upgradeable to 160 GB tested. some models have built-in Wi-fi. BIOS are interchangeable in S30 and S31 and tested to work. The latest known BIOS is 1.82.
Type 2607, or the Japan-only ThinkPad 235, is an interesting product because it is a progeny of the IBM/Ricoh RIOS project. Also known as Clavius or Chandra2, it contains unusual features like the presence of 3 PCMCIA slots and the use of dual camcorder batteries as a source of power. Features an Intel Pentium MMX 233 MHz CPU, support for up to 160 MB of EDO memory, and a built-in 2.5 inch hard drive with UDMA support. Hitachi markets Chandra2 as the Prius Note 210.
The ultraportable ThinkPad 240 (X, Z) started with an Intel Celeron and went up to the 600 MHz Intel Pentium III. The RAM was expandable to 192 MB max. With a 10.4 inch screen and an 18mm key pitch (A standard key pitch is 19mm). They were also one of the first ThinkPad series to contain a built-in Mini PCI card slot (form factor 3b). The 240s have no optical drives and an external floppy drive. An optional extended battery sticks out the bottom like a bar and props up the back of the notebook. Weighing in at 2.9 pounds (1.3 kg) these were the smallest and lightest ThinkPads ever made.
ThinkPad 300 series
The 300 series (300, 310, 340, 350, 360, 365, 380, 385, 390 (all with various sub-series)) was a long-running value series starting at the 386SL/25 all the way to the Pentium III 450. They were a bit large and slower than the more full-featured models but offered a less expensive ThinkPad.
ThinkPad 500 series
The 500 series (500, 510, 560 (E, X, Z), 570 (E)) were the main line of the ultraportable ThinkPads. Starting with the 486SX2-50 Blue Lightning to the Pentium III 500, these machines had only a hard disk onboard. Any other drives were external (or in the 570's case in the ultrabase). They weighed in at around 4 pounds (1.8 kg) and because of their excellent design are still in use today.
ThinkPad 600 series
The 600 series (600, 600E and 600X) are the direct predecessors of the T series, and are legendary for their portability, comfortable keyboard, and sturdy construction. The 600 series packed a 12.1" SVGA or a 13.3" XGA TFT LCD, Pentium MMX, Pentium II or III processor, full-sized keyboard, and optical bay into a package weighing roughly 2.3 kg (5 lb). IBM was able to create this light, fully featured machine by using lightweight but strong carbon fibre composite plastics. Battery life is said to be bad.
ThinkPad 700 series
The 700 series (700, 701, 730 (tablet), 750, 755, 760, 765, 770 (many with sub-models)) were the cutting-edge Intel-based ThinkPads. They featured the best screens, largest hard drives and fastest processors available at the time. This was the first successful ThinkPad introduced in 1992 (the first ThinkPad was a tablet PC without a keyboard and a mouse).
ThinkPad 800 series
The PowerPC ThinkPad series, (800/820/821/822/823/850/851/860) were unique in that they ran on the PowerPC architecture, and not the x86 architecture. They all used the PowerPC 603e CPU, at speeds of 100 MHz, or 166 MHz in the 860 model. The 800 may have used a 603, and it is unclear if the 800 was experimental or not. All units used SCSI 2 instead of IDE. The units are believed to have all been extremely expensive, as the 850 cost upwards of $12,000 USD. The 800 series can run Windows NT 3.5 (probably 4.0 as well), OS/2, AIX 4.14, Solaris Desktop 2.5.1 PowerPC Edition, and Linux.
The ThinkPad TransNote was a pen-based PC in a notebook. Data could be entered through the keyboard, TrackPoint, paper notepad (with writing sensor below), or the screen via stylus. This ThinkPad expanded on IBM's previous pen based notebooks (360P(E), 730T(E), and 750(P)).
ThinkPad T20 series (T20, T21, T22, T23)
Mobile Pentium III or Mobile Pentium III-M, sub-5 lb (2.3 kg) class machines. Contained processors ranging from 0.18 micrometre Mobile Pentium III 650 MHz to 0.13 micrometre Mobile Pentium III-M 1.20 GHz. Typically had 14.1 inch XGA screens, Ultrabay 2000 optical drives, S3 Savage/IX-MV graphics chip and Cirrus Logic CS 4614/22/24 sound chips; although variations along the line existed. Introduced the ThinkLight, a LED mounted inside the upper screen lip that illuminates the keyboard (activated with Fn-PgUp, the extreme diagonal keys); and titanium-reinforced and rubberized screen lids. Used MiniPCI form factor cards, which could be modem and/or ethernet. With the T23, an internal WiFi antenna became available, so WiFi miniPCI cards could be used. These models did not contain the active hard drive protection or touchpad pointing device which appeared in later models. They were clad in black non-slip rubber with embedded glitter. The case lid had tabs along the edge that interlocked with depressions in the lower case when closed, to reduce case flexing. Comparatively more stylish, functional, and rugged machines; and easy to disassemble for repair or upgrades.
ThinkPad T30 series
Solely includes the T30 model. Features include an Intel Mobile Pentium 4 processor ranging from 1.6 GHz to 2.4 GHz. Any T30 model may accommodate up to a 2.4 GHz processor with the latest BIOS and Embedded Controller upgrades. Graphics are provided by ATI Radeon Mobility 7500 hardware with 16 MB of discrete video memory, which supports external widescreen resolutions. Users have even reported success with output resolutions of 1920x1200 via DVI on the optional Port Replicator II docking station, although IBM claims a limit of 1280x1024 due to a weak TMDS transmitter. The T30 was available with a 14.1 inch screen, with resolutions of 1024 x 768 and 1400 x 1050. DVI video output is available with the optional Port Replicator II docking station, but resolution is officially limited to 1280x1024. Features available include the embedded security subsystem, UltraNav touchpad, 256 MB standard memory (1 GB maximum according to IBM manual, but it has been reported  to accept 2 GB of RAM), a 20, 40 or 60 GB hard disk, Ultrabay Plus drive, wireless, and Bluetooth. The T30 also contains a miniPCI slot usable for a wireless card. The shell is titanium-reinforced composite. The whole package was a bit heavier and thicker than the T4x series.
ThinkPad R40 series
This line of notebooks includes the R40 and the R40e.
An ultraportable IBM X31 with an IBM T43 notebookThinkPad T40 series
Includes the T40, T41, T42, T43, and associated "p" series (for "performance"; e.g., T43p). A typical 14.1 inch T4x weighs 2.2 kg (4.9 lb), slightly less than the 600 series, and features an Intel Pentium M Processor (ranging from the Intel Pentium M at 1.3 GHz to the Intel Pentium M 770 at 2.13 GHz), a 14.1 or 15 inch LCD (XGA, [[SXGA+]]), an integrated GPU (Intel Graphics Media Adapter 900) or a discrete GPU (Radeon x300, 7500, 9000, Fire GL 9000, 9600, Fire GL T2, X300, and Fire GL V3200), and a hard drive ranging in size from 30 to 100 GB with the Active Protection System to protect the hard drive (T41 and later models). "p" (mobile workstation) models are also available with a 14 inch SXGA+ or a 15 inch SXGA+/UXGA FlexView display with wide viewing angle and high density IPS technology. These 15-inch display models weigh slightly more than their lesser brethren, with optical drive and battery, at 2.7 kg (5.9 lb). All T4x models use either 6-cell or 9-cell lithium-ion batteries, as well as an optional 4-cell Ultrabay Slim lithium-polymer battery. Some T42 and T43 models feature a biometric security system with built-in fingerprint reader. Some types of the model also had the option to include Bluetooth support. The T40 was IBM's first ThinkPad to use the Pentium M "Banias" CPU. The T42 employed a Pentium M "Dothan" processor with a 400 MHz frontside bus, while the T43 used a later revision Dothan running a 533 MHz FSB.
ThinkPad R50, R51, R52 series
Based on the T40 series, this line of notebooks includes the R50, R50e, R50p, R51, R51e and R52. The R52 is the first R-series notebook to utilize DDR2-memory and include a SATA-controller, however uses only PATA-harddrives, just like its origin, the ThinkPad T43. This series of notebooks is available with fingerprint-readers and uses many components also found in T40-series models, such as batteries, keyboards and planars (system boards).
ThinkPad T60 series
Includes the T60, T61; and associated "p" series (for "performance"; e.g. T60p); intended as the next generation of the T4x Series ThinkPads; this is the first T Series ThinkPad to include the Intel Core Duo "Yonah" Technology, and later the Intel Core 2 Duo "Merom" Mobile technology; and the first T-series ThinkPads to come in widescreen resolution. This model has a VMX-enabled BIOS (although the lowest end Intel Core CPUs themselves do not support VMX, such as the T5500), meaning that running fully virtualised operating systems via Xen or Vmware is possible. The T61, announced in May 2007, features a widescreen resolution as the default resolution, and incorporates the Intel Santa Rosa platform having a fully 64-bit chipset, and is the first T-series ThinkPad to have an integrated web camera (optional), smart card reader (optional), and media card reader (optional). Furthering innovation founded in the T60, the T61 also sports a top-cover roll cage, aside from the magnesium roll cage inside the main chassis.
ThinkPad X20 series (X20, X21, X22, X23, X24)
Pentium III Mobile, sub-4 lb machines. Contained processors ranging from PIIIM 500 MHz to PIIIM 1.13 GHz. 12.1 inch XGA screens, and ATi Rage Mobility M1 (X20, X21) or Radeon Mobility M6 (X22, X23, X24) graphics chips. Used miniPCI form factor cards, which supports modem and/or ethernet. With the X22 and later machines, provisions for wireless networking support are built into the chassis. Ultrabay 2000 optical drive support can be fitted via the Ultrabase portable docking station option, and extended batteries can give the series a 5-hour running time.
ThinkPad X30 series (X30, X31, X32)
Pentium III Mobile (X30), Pentium M Banias (X31) or Pentium M Dothan (X32), 12.1 inch XGA screens, dedicated Graphic Chip (ATI M6 with 16 MB, which means no shared memory is cut from the RAM), Bluetooth on some models (upgradable), WLAN (b, b/g or even a/b/g), FireWire, Compact Flash card slot. No built-in optical drive. Lots of options like second battery, Mediaslice (for battery and Ultrabay), port replicators, docking stations (some with a PCI slot).
ThinkPad X40 Series
An example of the lightweight X series, weighing in at 1.2 kg (2.7 lb), 25% lighter than its predecessor, the X31. The last variant of the X40 series, the X41 Tablet, was the first ThinkPad tablet PC since the original pen-based ThinkPad. It is the lightest 12" Tablet PC with a keyboard from any manufacturer. It was also the final released ThinkPad designed by IBM before the brand was purchased by Lenovo.
ThinkPad X60 Series
Includes the X60 and X61, with their associated "s" and "Tablet" series. The X60 is first X Series ThinkPad to feature Intel chips using the Intel Core architecture. The Core Duo L2400 (Low Voltage) CPU on the X60s model achieves 7+ hours of battery life on standard benchmarks, and can reach around 10 hours under light use, when using the extended-life battery. Note this model lacks a built-in optical drive, unlike the larger T60. The X61, like the T61, also is the first X-series ThinkPad to use Intel's Santa Rosa platform.
ThinkPad Z60 Series
This is the first ThinkPad to feature a widescreen (16:10 aspect ratio) display. The Z Series is also the first ThinkPad equipped with titanium lid (on some models). Integrated WWAN and/or webcam found on some configurations too. Includes, as of 2006, the Z60 and Z61; the latter of which is the first Z Series ThinkPad with Intel "Yonah" Dual Core Technology. The processor supports Intel VT, it's disabled in the BIOS and can be turned on thanks to a BIOS update. So running fully virtualised operating systems via Xen or Vmware is possible.