contents of the serial EEPROM. Tandy 1000 SL and TL series The Tandy SL and TL series of computers are updates of the SX and TX, respectively. In addition to offering redesigned cases, the machines offer a more integrated motherboard with improved graphics and sound capabilities while dropping composite video output. The graphics controller supports resolution as well as a Hercules Graphics Card-compatible, mode for monochrome monitors. Sound capabilities now include an 8-bit monaural DAC/ADC similar in function to parallel port sound devices (such as the Covox Speech Thing and Disney Sound Source) but extended to support DMA transfers, microphone input capability, and sampling rates up to 48 kHz. The SL/TL allow the on-board floppy controller, parallel port and serial ports to be disabled, which the earlier models do not. The SL and TL were shipped with MS-DOS 3.3 and DeskMate 3 in ROM, and feature a serial EEPROM memory chip to store BIOS settings. The machines can also run generic MS-DOS 3.x, 5.x, and 6.x and Windows 2.x and 3.0 operating systems, although Windows is limited to real-mode operations. In common with many PC clones of the era, MS-DOS 4 is problematic and generally avoided. 1000 SL and SL/2 The Tandy 1000 SL and SL/2 feature an Intel 8086 processor running at 8 MHz. This is socketed, and thus upgradeable with an NEC V30. The SL comes with of RAM preinstalled, whereas the SL/2 offers . Both machines can be expanded to , although the graphics controller reserves a portion of this memory, yielding only to the operating system, even on systems using add-in ISA graphic cards. The SL line has the mic/earphone ports, volume knob, and reset button on a small satellite board. A jumper on the board allows the user to change the microphone input to a line-level output. The SL series offers five 8-bit XT-compatible ISA slots, and does not come with pre-installed real-time clock chips, making them optional upgrades in the form of the plug-in Dallas DS1216E SmartWatch. The SL is the only machine in the line that offers an upper 5.25" bay, and therefore the only model to offer two 5.25" bays, where the other models, including the SL/2 and the entire TL range, feature two upper 3.5" bays and one lower 5.25" bay. As a result, fitting a hard drive to an SL that already has the upper and lower 5.25" bays populated