The Alpha 21264 CPU: NT's Greatest RISC (1998)

91 points74 comments19 hours ago
ggm

My memory is that the Alpha and OSF/1 hit at the same time. OSF/1 had a different model of shared library stuff, and I recall it being something which sometimes demanded a reboot to get a runtime cache rebuilt/linked so things worked as you expected. I may be mis-remembering, I think DEC had coded some pull up smarts to optimise the lib -> indirect -> actual call path into the shortest path possible.

I also recall the syslog being absolutely FLOODED with "unaligned access at..." messages.

It was fast. It was very fast. If you knew how to make the compiler to the precompile, test run, introspect, recompile cycle, it would work out from some sample state the right choices (branch prediction ordering?) and make your fast code even faster.

hinkley

Digital, HP, and IBM had the foresight to supply NCSA with Windows NT machines with their respective not-Intel chips in them to make sure that they had a web browser on their platforms. I got the honor of using the Alpha machine, and so it got the most QA by far. I recall spending an unnecessary amount of time not only staring at the heat sink but occasionally showing it to the new guy so they could confirm my astonishment.

Having the free hardware mostly worked, but there was a long time before all of the data alignment bugs got sorted out. It got to the point where my CS classes had progressed enough that I started looking for them myself. Literally the first development tasks I got paid to do was code reviewing for word alignment bugs on 64 bit code. It was a long goddamned time ago so it's pretty fuzzy but IIRC not all 3 processors had exactly the same restrictions for all data types. So if it worked on Alpha it usually worked on the other 2 but not 100%.

I didn't have to deal with 64 bit software at work again for another 10 years, at which point people looked at me like I was trying to be edgy when I just shrugged. No, really, I was looking at 64 bit code errors 10 years ago.

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MomsAVoxell

In those days, I was using SGI machines to build web sites for folks .. the Indy was very popular for this purpose. One day I was given a DEC Alpha machine to evaluate and see if it was a worthwhile addition to our inventory.

It came with NT, so there was some friction to just adding it to our services. These days were very frustrating - Microsoft was hell-bent on killing Unix, and later Linux also - and there was a lot of back and forth in our engineering team whether we wanted to invest in this hassle.

We didn't. I had that machine under my desk doing basically nothing for a year, before I sent it back.

If there had been a bit more insight into the nature of things, and if it had been running a Unix variant, we would have given it a better chance.

So then it was even more frustrating when SGI did a deal with the devil in later years, and tried to get its customers switch to NT, also. That killed SGI, in my opinion.

Looking back now, it's kind of incredible the resistance to Unix in those days, and how it was all going to be replaced with some "New Technology". Linux won. SGI didn't. And DEC was an early victim they should have learned from, in my opinion.

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leoc

A 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 )

fredoralive

The bit about how the AMD Athlon (K7) uses the same bus, and how they planned to make Slot A Alphas where the only adjustment an Althon motherboard would need is a different BIOS. Imagine what might have been, especially as Alpha Windows 2000 had a built in FX!32. Cheap Alpha systems with a good x86 compatibility story, it could've been a contender.

(Yeah, I know, several stars would've had to align for it to actually work).

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jleyank

I 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.

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loph

It's important in the historical context of the Alpha AXP to also remember the DEC PRISM architecture. Canceled in 1988. One of many architectures killed off by DEC.

https://en.wikipedia.org/wiki/DEC_PRISM

Killing Prism sent David Cutler into the arms of Microsoft.

Another dead architecture was Jupiter: https://en.wikipedia.org/wiki/Jupiter_project

Killing Jupiter sent many of DEC's DECsystem-10 customers to IBM.

Years later, they both seem like bad decisions.

rbanffy

It’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.

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dosinga

> outside of the highly specialized embedded-application market, RISC is in retreat

with hindsight it is funny to realize that RISCs come back would start from inside that highly specialized market in the form of ARM.

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theandrewbailey

From back when IA-64 (A.K.A. Itanium) was supposed to take Intel to the promised land.

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stmw

Fun fact - Linus first trip to the United States was related to Linux-on-Alpha port and sponsored by Digital Equipment Corporation.

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rayiner

Man, I loved reading Tom’s articles in BYTE.

irusensei

I heard about Alpha in that it while being more powerful than x86 it wasn't as alien as the competition. The boards had PCI slots and looked like normal PCs, it had Windows NT and Linux. So if your Exchange server was not handling the load you moved it to Alpha and it was good.

It also seems faith in IA64 was the meteor that killed most of these self developed RISC architectures.

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EvanAnderson

> 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... >sigh<

I 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.

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hinkley

BYTE magazine has been gone for almost 30 years now. Fuck.

Dr Dobbs has been gone for 12, which is still a long time, but when I first read the intro my brain transposed the two and I had a proper freak out before I realized what I'd done.

robin_reala

I remember Byte folding, but I’d blanked that it was a full 28 years ago.

chasil

For everyone who says that the Alpha was a technically-superior CPU design that should have prevailed, I will draw attention to an interesting fact:

"According to Allen Baum, the StrongARM traces its history to attempts to make a low-power version of the DEC Alpha, which DEC's engineers quickly concluded was not possible."

https://en.wikipedia.org/wiki/StrongARM

While AArch64 has been in the top supercomputer, a phone running on Alpha was not.

For this scalability problem, it deserved to die.

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danielktdoranie

Hardly anyone ran NT on these beautiful chips. Tru64 was the OS of choice for these in 1998. Hence the decision by MS to cease support. Running NT on a Dec Alpha would be like running kerosene in your Ferrari’s engine. If you wanted to run Windows NT you could do so a lot cheaper on an x86 PC.

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