The A4000T, also known as the Commodore Amiga 4000T, was a tower version of the A4000 computer. This was originally released in 1994 with a 25 MHz Motorola 68040 CPU, and rereleased after Commodore's demise in 1995 by Escom, along with a new version which featured a 50 MHz Motorola 68060 CPU. It was only produced in small numbers.
The A4000T was the only Amiga ever to have both SCSI and IDE interfaces built-in on the motherboard. Having driver software for both interfaces on the ROM meant that some other parts of AmigaOS had to be moved from the ROM, and thus the A4000T is the only machine to have the file "workbench.library" stored on disk. It was also the only Amiga to use a PC form factor for the motherboard, and one of the few to use a Lithium Ion backup battery instead of a NiCd. This backup battery is also one of the most common causes of problems in the aging A4000s: it has a tendency to eventually leak. The released fluids are somewhat corrosive and can eventually damage the motherboard.
This was the final machine to be put out by Commodore International. Only a couple of hundred 4000Ts were produced before the whole company folded. Production of the 4000Ts was restarted after Escom bought the Amiga assets. Apart from the new option of a 68060 CPU, the Escom-manufactured 4000Ts had minor differences with the old one, including the substitution of the high density floppy drive with a double density one. From Wikipedia