SNK's Neo Geo CD was released in 1994, four years after its cartridge-based equivalent, in an effort to reduce manufacturing costs. The system was originally priced at US$300 new. The unit's (approximately) 1X CD-ROM drive was slow, making loading times very long with the system loading up to 56 Mbit of data between loads. Neo Geo CD game prices were low at $50, in contrast to Neo Geo AES game cartridges which cost as much as $300. The system could also play Audio CDs. All three versions of the system have no region-lock.

The Neo Geo CD was bundled with a control pad instead of a joystick like the AES version. However, the original AES joystick could be used with all 3 Neo Geo CD models, instead of the included control pads.

Specifications

Main Processor: Motorola 68000 running at 12 MHz
Although the 68000 CPU was designed by Motorola, there were many other clones of this CPU found in the Neo Geo hardware. The most common CPU is the TMP68HC000 manufactured by Toshiba. This is essentially a Motorola 68000 clone.
Co-Processor: Zilog Z80 running at 4 MHz
Colors On Screen: 4,096
Colors Available: 65,536
Resolution: 304 x 224
Max Sprites: 380
Max Sprite Size: 16 x 512
Number of Planes: 3

The system is also capable of reading Redbook standard compact disc audio.

In addition to the multi-AV port (almost same one as used on the Sega Genesis model 1, though they are not interchangeable.) all Neo Geo CD models had composite RCA A/V and S-Video out jacks on the rear of the console.

The CD system's 58 Mbit / 7 MB of RAM was split accordingly:
68000 Program Memory: 2 MB
Fix Layer Memory: 128 KB
Graphics Memory: 4 MB
Sound Sample Memory: 1 MB
Z80 Program Memory: 64 kB
VRAM: 512Kb (For graphics attributes)
SRAM: 2 KB (For high scores / general save data)

Source: Wikipedia, "Neo-Geo CD," available under the CC-BY-SA License.