Designed as an entry level PC compatible computer, the Tandy 1000EX was released in 1987, and primarily marketed against the IBM PCjr. The 1000EX was a compact computer with an integrated keyboard, and a 5.25" 360k floppy drive integrated into the right side of the case. The computer came with 256kB of RAM, MS-DOS/GW-Basic 2.11, and DeskMate. DeskMate was unique for the time, having previously been released for the CoCo under OS-9, and contained useful apps like a text editor, spreadsheet, calculator, notepad, calendar, phone directory and a paint style application. Many of the same apps integrated into modern computers. This system initially sold for $799, and an upgrade to MS-DOS was available for $29.99.
The CPU in the 1000EX was the Intel 8088, with software selectable speeds of 7.16/4.77MHz the PC did boot at 7.16MHz by default. While the computer shipped with 256k of RAM, it was upgradable to 640k via add-on cards. Internally, there was one expansion slot that, when used with the RAM expansion card, would give you two additional expansion slots. Display resolution was switchable between 80 or 40 characters by 25 lines. Green or CGA
Released in 1988 and appearing Tandy computer catalogs in 1988, the Tandy 1000HX was considered the 'bigger brother' of the 1000EX. It was still considered an entry level PC. Much of the internals were the same as the orginal EX, but there were a few differences. For example, MS-DOS 2.11 was contained in ROM (read only memory), which lead to faster boot times. To access the ROM based DOS, one only needed to power up the PC without a bootable disk in the now 3.5" floppy drive, located in the front of the case, instead of the right side. Like the 1000 EX, The 1000HX defaulted to the 7.16MHz in it's identical Intel 8088 CPU, with 4.77MHz being available, selecable by software requirements.
Both the 1000 EX and HX would take the same 640kb Plus card memory upgrade, which also allowed for DMA access. The Plus card was electrically identical to the well established ISA slot standard, but used a Berg style 62 pin connector instead of the ISA style connector. Other PLUS cards could be installed to add serial ports, a 1200 baud modem, a clock/calendar and bus mouse board and a proprietary Tandy network interface.
The Tandy 1000EX and 1000HX are similar to the earlier 1000s except now they are using the NCR8496 chip for audio, which are essientially clones of the TI SN76496, as well as the real TI SN76496s. The TI SN76489 audio chip was used in many different computers and video game consoles of the day, including the Sega Master System and Genesis. While the two chips (NCR & TI) work almost identically, there are differences, mostly requiring slightly different electrical components on the motherboard, and it's really a coin-flip as to which chip you would get when buying one of these machines. If you want a more technical description of the differences, this link to Nerdly Pleasures has a far more indepth analysis than I'm willing to go into.
For video, both models had the same options. There was an RGBI interface for using the standard Tandy CGA graphics with a 9 pin Tandy monitor. Additionally, both the 1000EX and HX came with composite video output, in order to use the PC with a television set. The 1000 HX was the last Tandy computer to be so equiped, ending a feature that started with the first TRS-80 Color Computer.