Both are based on an 800MHz version of the TM5800 Crusoe processor from Transmeta, have a 10-inch widescreen TFT screen capable of 1,280 by 600 pixel resolution, 256Mbytes of memory, a 20Gbyte hard-disk drive, ATI Technologies' Mobility Radeon M graphics accelerator, an Ethernet port and slot for Toshiba's Secure Digital (SD) memory card.
The major difference is an internal wireless LAN adapter in the L5/080 TNKW model and the fact that it runs the Windows XP Professional operating system. The L5/080 TNKN has no built-in wireless adapter and runs Windows XP Home Edition.
These are also two of the biggest differences between the new L5 series machines and the previous models, which did not include wireless support and ran the Windows 2000 or Windows ME operating systems. The previous model also used a slower 600MHz Crusoe processor.
The new Libretto models have a battery life of 4.5 hours.
Toshiba's launch comes a week after Sony announced its new Vaio C1 and Vaio U1 sub-notebook computers. The Vaio C1 comes closest to the Libretto in terms of looks but runs a slightly faster 867MHz version of the same Crusoe processor and has a smaller 8.9 -inch widescreen LCD that manages the same resolution.
The Vaio U1 is a class smaller, based on the 867MHz processor but fitted out with a 6.4-inch LCD. When Sony launched the computer the company claimed it was the smallest Windows XP machine on the market - something that the new Libretto does not change. While the Sony machine may win on size and weight, road warriors will appreciate the Toshiba's larger keyboard.
The new machines will go on sale in Japan on Friday and the wireless model will sell for around ¥170,000 (£908) while the non-wireless model will cost around ¥140,000 (£748). A day later, Sony will put its Vaio C1 and U1 models on sale at ¥230,000 (£1,229) and ¥150,000 (£801) respectively.
Toshiba has no plans to sell its Libretto range overseas at present.