The Digital UDB computer is also known as a Multia. It's about the size of the current mini-PC boxes known as book computers. Multias have on board video and ethernet, sound, two serial and one parallel, two PCMCIA/PC Card slots and SCSI.
The first Multia and most common, has a 166MHz Alpha processor. They were a marketing disaster, since the target was to use them as office machines. They only ran Windows NT or Digital UNIX and didn't work with x86 binary applications. There was eventually a binary emulation package, but it didn't help much because the CPU was relatively slow even without emulation.
They eventually got around to doing a Pentium 100 version of the Multia. Apparently extremely rare. It's a Socket 7, and you can put a 233MHz Pentium MMX replacement. Decent box if you can find this upgrade. They take basic SIMMs up to 128MB. The on board video is a S3 968, and the sound is a AD1848 "Windows Sound System".
The Pentium versions make good little Linux workstations. The Alphas are slow, but maybe useful if you get one absolutely dirt cheap and don't need to run any binary-only software.