The Alpha 21264 CPU: NT's Greatest RISC (1998)
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The Alpha 21264 CPU: NT's Greatest RISC (1998)
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Re: The Alpha 21264 CPU: NT's Greatest RISC (1998)
#2It’s so good to re-read Tom Halfhill’s articles. I wonder where he’s been in the past… checks notes… 30 years I haven’t seen his writings.
Re: The Alpha 21264 CPU: NT's Greatest RISC (1998)
#3From back when IA-64 (A.K.A. Itanium) was supposed to take Intel to the promised land.
Re: The Alpha 21264 CPU: NT's Greatest RISC (1998)
#4> David Jessel, the Alpha's senior product manager, claims that Alpha fans have nothing to worry about. "Compaq has been fully supportive of the Alpha and is continuing to invest in it," Jessel said.
That worked out swimmingly for Alpha... >sighI never programmed Alpha assembly, so I don't really have a feel for the architecture. I did deploy some Alpha-based boxes running NT, and they were very nice. They didn't feel pieced-together like x86 servers did.
Re: The Alpha 21264 CPU: NT's Greatest RISC (1998)
#5I seem to remember that Alpha’s were very fast for the time but their maximum optimization level waived IEEE floating point conformance. This, of course, drove us nuts trying to validate ports of numerically intensive code. Less interesting chips with lower optimization and limited market penetration.
Now, HP’s PA-RISC chips…. Those things were fast and easier to work with. Curiously, with SoftPC they could do windows faster than a 486 could. Slaughtered all sorts of mini-supers they did.
Would have been interesting if alpha survived to compete with SGI’s MIPS.
Re: The Alpha 21264 CPU: NT's Greatest RISC (1998)
#6[dead]
Re: The Alpha 21264 CPU: NT's Greatest RISC (1998)
#7I seem to remember that Alpha’s were very fast for the time but their maximum optimization level waived IEEE floating point conformance. This, of course, drove us nuts trying to validate ports of numerically intensive code. Less interesting chips with lower optimization and limited market penetration. Now, HP’s PA-RISC chips…. Those things were fast and easier to work with. Curiously, with SoftPC they could do window…
I worked on the first PA-RISC workstations (“snakes”, 1989-1991). PA-RISC started as a fairly pure RISC design and was consequently very simple and predictable (short pipeline, 1 delay slot, no complex instructions). The philosophy of the design team was to make the system fast with high clock speeds, short pipelines, and big caches, all big fundamental variables in the performance equation.
Alpha was much more sophisticated but also a lot more complex. The Alpha memory model, in particular, was quite complex with lots of cache control and barrier primitives, IIRC. But it could fly when you got the stars to align.
Edit: Alpha also came out later and PA-RISC also got more complex in later generations.
Re: The Alpha 21264 CPU: NT's Greatest RISC (1998)
#8I seem to remember that Alpha’s were very fast for the time but their maximum optimization level waived IEEE floating point conformance. This, of course, drove us nuts trying to validate ports of numerically intensive code. Less interesting chips with lower optimization and limited market penetration. Now, HP’s PA-RISC chips…. Those things were fast and easier to work with. Curiously, with SoftPC they could do window…
what did they not implement from 754? Given the design of the processor i can imagine them being very aggressive with assumptions around exception handling / traps - iirc this is actually the original reason why Tomasulo algorithm exists because the first out-of-order processors didn't actually make any guarantees about the order that you would observe these side effects.
Re: The Alpha 21264 CPU: NT's Greatest RISC (1998)
#9I remember Byte folding, but I’d blanked that it was a full 28 years ago.
Re: The Alpha 21264 CPU: NT's Greatest RISC (1998)
#10A video of an 1994 presentation put together for Hot Chips VI on the 21164: https://youtube.com/watch?v=OHupqMbLj1g
An April 1992 University Video Communications presentation on the Alpha architecture https://youtube.com/watch?v=klg1FtHADso and then from 38m 19s on the 21064 CPU https://youtube.com/watch?v=klg1FtHADso&t=2299s . From about 2m52s https://youtube.com/watch?v=klg1FtHADso&t=172s to 4m 43s Richard L. Sites gives the Alpha team’s predictions from 1992 for the next 12-25 of CPU development, which seem to have been fairly on the nail.
(Sites hasn’t been idle recently either! He’s responsible for the ultra-low-overhead KUTrace: https://news.ycombinator.com/item?id=40972099 )