A Tribute to Michael Abrash: The ISA

Some people idolize athletes. Others gravitate towards entertainers. While Derek is a hockey fan and a musician who loves watching movies, his real passion lead him in a different direction. And he's also going to devolve into first person singular for a minute to tell you a little more about that.

At the time I was a high school student who needed a good project outside the curriculum to teach to our C++ programming class (this was another one of the excellent projects Jo Adams set her students upon). My good friend Tom Macleod and I had just learned enough calculus and advanced geometry to be dangerous: we decided to write a 3D graphics engine in order to learn and teach graphics programming to the class.

To support this endeavor, I spent a bit of cash (well, my parent's cash anyway) on some graphics and game programming books for the occasion, and the one that really stood out (the one that set the course of my life) was Michael Abrash's Graphics Programming Black Book Special Edition. This giant tome contained quite a bit of collected wisdom regarding the art and science of code optimization and graphics programming as well as some great details about the development of Quake.

Not only was his book an incredible source of information and inspiration for me personally, but if there was ever an x86 assembly guru and graphics programming god that could help take the design of an instruction set architecture for Larrabee to a whole other dimension, it is Michael Abrash. And our information indicates that he has done just that.

This isn't to say that others on the Larrabee team don't deserve a spotlight; it's just exciting to see the guy who got me hooked on computer graphics programming (which lead to my interest in hardware) show up on such an impressive graphics hardware design team.

For those who haven't idolized Abrash, his Wikipedia entry helps explain his luminary status in the game industry:

"Michael Abrash is a highly regarded technical writer, and one of the top optimization and 80x86 assembly language programmers, a reputation cemented by his 1990 book Zen of Assembly Language Volume 1: Knowledge. Before getting into technical writing, Abrash was a game programmer, having written his first commercial game in 1982. After working at Microsoft on graphics and assembly code for Windows NT 3.1, he returned to the game industry in the mid-1990s to work on Quake for id Software. Some of the technology behind Quake is documented in Abrash's Graphics Programming Black Book. After Quake was released, Abrash returned to Microsoft to work on natural language research, then moved to the Xbox team, until 2001. In 2002, Abrash went to work for RAD Game Tools, where he co-wrote the advanced Pixomatic software renderer, which emulates the functionality of a DirectX 7-level graphics card and is used as the software renderer in such games as Unreal Tournament 2004."

Intel brought Abrash on as a consultant to help define the Larrabee instruction set. For the longest time, extensions to x86 (e.g. SSE4) were done by Intel engineers at the request of the software community. With every iteration of SSE the game industry was always happier but never truly satisfied with the extensions to x86 that Intel introduced. When Intel set out to define the extensions to x86 that would be used in Larrabee, it sought out visionaries within the game industry to help define that spec rather than creating hardware and defining the ISA internally. One thing we've consistently heard from game developers about Larrabee is that the ISA makes more sense than any other approach they have seen from ATI or NVIDIA. Larrabee's ISA was designed in part by the game industry, for that very industry.

Interestingly enough, while reluctant to go into details about the Larrabee ISA itself, Intel did tell us that fewer than 5% of the instructions are graphics specific. What they found is that creating overly specialized instructions doesn't always do that much good as they can be hard for compilers to use effectively and difficult to hand optimize with as well. Rather, having a good selection of generally applicable and powerful instructions is a better way to go.

One of the advantages of developing the compiler in parallel with the ISA itself is that they can easily test and adapt both as needed to understand how best to balance the ISA. As the vast majority of developers will rely on compilers to generate highly performant code, making sure the ISA is a good fit for compilers is essential. At the same time, because of the renewed interest in software graphics engines Larrabee is stirring up in the Old Guard of real-time 3D computer graphics, having icons like Michael Abrash on the team will help make sure that the ISA is not only compiler friendly but will also be attractive to those who wish to achieve Zen through assembly optimization.

Which brings us to an interesting point.

Programming for Larrabee The Awesome Potential of Fully Programmable Graphics
Comments Locked

101 Comments

View All Comments

  • ocyl - Monday, August 4, 2008 - link

    Larrabee will be shipped when Diablo III is, and it will mark the beginning of the end for DirectX.

    Calling it first here at AnandTech.

    Thanks go to Anand and Derek for the very well written article. You are the ones who keep tech journalism alive.
  • erikespo - Monday, August 4, 2008 - link

    "At 143 mm^2, Intel could fit 10 Larrabee-like cores so let's double that. Now we're at 286mm^2 (still smaller than GT200 and about the size of AMD's RV770) and 20-cores. Double that once more and we've got 40-cores and have a 572mm^2 die, virtually the same size as NVIDIA's GT200 but on a 65nm process. "

    this math is way off

    143 mm^2 is 20449mm.. if they fit 10 there that is 2044.9 per core
    286mm^2 is 81796mm.. that is 4X the space so 40 cores in 286^2
    and 572mm^2 is 327184mm is 160 cores..

    double length will double area.. doubling length and width will quadruple area.
  • bauerbrazil - Monday, August 4, 2008 - link

    Hahahaha, YOUR math is way off!!!

    Jesus.
  • erikespo - Monday, August 4, 2008 - link

    I see where the article and you got your math..
    you both did 143mm^2 / 10 and got 14.3 then divided 286^2 by 14.3 and got 20.. this math is only acting on the one number..

    I know this because the area of 14.3 is 204.49 mm. 10 of those would be 2044.9mm. but the area of 143mm^2 is 20449mm.
  • WeaselITB - Monday, August 4, 2008 - link

    Wow ... No.
    143mm^2 is NOT equivalent to 143^2 mm ... Your analysis is flawed.

    If we use your example, 2mm^2 is NOT 2mm x 2mm ... it's actually root(2)mm x root(2)mm ... 4mm^2 is 2mm x 2mm, not 4mm x 4mm (that'd be 16mm).

    Maybe you should examine in depth that Wikipedia article you linked earlier ...

    Thanks,
    -Weasel
  • MamiyaOtaru - Monday, August 4, 2008 - link

    143mm^2 is NOT equivalent to 143^2 mm

    ^^THIS

    That's it in a nutshell. mm² doesn't mean you square 143, it refers to Square Millimeters, a unit of area (unlike Millimeters, a unit of distance).

    Revised mspaint illustration: http://img379.imageshack.us/my.php?image=squaremmh...">http://img379.imageshack.us/my.php?image=squaremmh...
  • erikespo - Monday, August 4, 2008 - link

    Anandtech Comment Section.. Forever record of my retardedness
  • erikespo - Monday, August 4, 2008 - link

    Dang.. Many apologies..
    got my square area and squared numbers confused..
  • WeaselITB - Monday, August 4, 2008 - link

    [quote]4mm^2 is 2mm x 2mm, not 4mm x 4mm (that'd be 16mm).[/quote]

    Dang, that was supposed to read "(that'd be 16mm^2)."

    Thanks,
    -Weasel
  • erikespo - Monday, August 4, 2008 - link

    another way to look as it is how man 143mm^2 squares does it take to make up 286mm^2?

    only 2 would only be 143mm x 286mm

    since 10 cores fit into 143 x 143, 20 will fit into 143 x 286mm
    286 x 286 (which is double that of 143 x 286mm) the 286mm^2 would fit 40

Log in

Don't have an account? Sign up now