AS/400
From MidrangeWiki
The original name for the ISeries still in use by many programmers and administrators. First sold in 1988, it was the direct successor to the System/38.
The original AS/400 hardware was based on a 48-bit proprietary CISC CPU, but was replaced in 1995 with a 64-bit PowerPC RISC CPU. Even though the hardware platform changed, very few programs needed to be changed or even recompiled.
Silverlake was the codename for the AS/400 project before it was released. It was considered by many to be one of the worst-kept secrets.
Also see the AS/400 write-up in [Wikopedia http://en.wikipedia.org/wiki/AS/400]