Paul Pierce &lt;prp(a)hf.intel.com&gt; wrote: The "classic" HP 3000 is identified by its series. Numbers <= 70, no designation at all, and the letters "CX" alone mean it's the classic stack machine. Numbers >= 900 mean it's a PA-RISC 3000. The first HP 3000s were shipped in November 1972, and were pretty much a disaster -- HP ended up recalling them. But they kept plugging at it and turned it into what I think is one of the finest transaction-processing systems available. I'm not sure when the last classics were introduced, but I think HP continued to sell some of the low-end ones (Micro 3000 GX/LX/RX) into the early 1990s, certainly into the late 1980s. The last of them go out of support life over the next year or so, though. HP 9000 series 500 (520, 540, 550, was there a 530?) are 32-bit stack machines inside, with the potential for multiple CPUs and IOPs on the larger systems. I think HP now has something called a T500 that is PA-RISC based; the old series 500s are pretty much forgotten (but not all gone, I have a 520 in storage that I need to reanimate). HP sold these from the early-to-mid 1980s before they were superseded by fast Motorola 680[23]0s and PA-RISC systems (series 300/400 and 800/700). -Frank McConnell "I want my MPE" (w/apologies to Dire Straits) &lt;fmc(a)reanimators.org&gt;