AMD Releases R700 Instruction Set

Last Thursday, AMD released a 392-page PDF (v1.0 dated March 2009) outlining the Instruction Set Architecture (ISA) native to the R700 family, and display a difference between the Radeon HD 4870 and the Radeon HD 4890.

Along with outlining the R700 ISA, AMD's loaded document also defines the instructions and formats accessible to the programmers and compilers, covering the RV710 (Radeon 4350/4550) on through to the upcoming RV790 (Radeon 4890). However, it isn't for the typical consumer looking to see what the R700 family has to offer, but rather is geared towards the programmer writing application and system software including device drivers, operating systems, system utilities and more. The document actually serves to help these programmers and compiler writers maximize processor performance. Still, it's a good way--especially for those who really enjoy the technical side of GPUs--to see what's under the hood, and the differences between a few of the GPU variants.

According to Chapter 7 in the PDF, the RV790 supports burst memory reads while the RV770 does not. "Burst memory reads are not supported by the RV770; however, the 710, 730, 740, and 790 do support it. Chips after R770 support burst reads in memory-read instructions. This allows up to 16 consecutive locations to be read into up to 16 consecutive General Purpose Registers (GPRs). This adds a new field BURST_CNT to MEM_RD_DWORD0," the document states. "For each iteration of the burst, the DST_GPR is incremented by 1 and the ARRAY_BASE is incremented by 1. The SRC_GPR is not affected." So because the RV770 series (Radeon 4870/4850/4830) does not support the burst memory read function, it's safe to assume that the RV790 (Radeon HD 4890) will work more efficiently.

As defined by AMD, burst mode read is a synchronous operation that is tied in to the rising edge of a clock; the microprocessor/microcontroller supplies only the initial address to the device. Using an architectural approach such as bust mode enables faster access times, as higher density and lower voltage tend to reduce performance in a standard random access memory architecture. With that said, devices using the burst mode architecture offer improvements in system speed and performance by reducing sequential read access times. Additionally, AMD burst mode devices have two different read modes: random read and burst mode read.

There's definitely quite a lot to read within the 392-page document, spanning ten chapters can covering topics such as control flow programs, memory read clauses, data share clauses, and microcode formats. To read more about the R700 family architecture details, download the PDF for AMD right here. Although the document contains 392 pages, the file weighs a mere 1.9 MB.

  • deltatux
    It's quite the interesting read but what is written in the article is correct, for the average gamer or consumers, this document either makes no sense to them or they just don't have interest in it.

  • jkeelsnc
    Well, finally after umpteen years of secrecy and BS ATI finally documents their hardware so someone in the Linux community can really write some great OPEN SOURCE (not proprietary) drivers for the hardware. More companies need to do this instead of locking the doors and hiding things. How can you trust a company your doing business with if it is all sneaky, hidden, hide everything, and cover up (kind of like the republicans for the last 8 years and Micros&*& for that matter). Companies stop hiding and give us the information so that we don't have to rely on Microsoft forever.
  • SAL-e
    deltatux... or they just don't have interest in it.deltatuxThey would had interest if it was clear that is key document needed to provide open source driver for Linux and other OSes that support OpenGL and full 3D hardware acceleration. So in the next one to two years we could start seeing very good games for other platforms like Linux, FreeBSD, etc.
  • megamanx00
    I suppose they are preparing developers to begin maximizing games for the 790. Probably would have been better if they released it a little earlier though ^_^. It's interesting that the RV730 (4670/4650) supports that burst read instruction. It will certainly help with the open source driver effort. I'd like to think it would help Linux programmers, but seeing as the main API available to them is Open GL 3, I'm not too sure. Open GL is just falling behind due to politics and some stubborn CAD developers in comparison to DirectX. Sad but true.
  • Soul_keeper
    Linux is for much more than "die hard microsoft haters"
    sorry pal but you are missinformed
  • Soul_keeper
    Really how do you figure ?
    My guess is you're a payed MS employee.
  • Soul_keeper
    LOL, you're a complete noob.
    I game in linux every day and havn't had a need for your MS junk for years.
    your 2% number is a complete joke(based off obscure numbers with a giant MS advertisement leading to it) as it don't account for the fact that the vast majority of webservers and mailservers are linux . Not to mention the enormous server/workstation base that MS don't tell you about in that FUD magazine that's rotted your brain.

    The simple fact of the matter is Linux gains market share every year, while MS loses market share every year.

    Judging from your complete ignorance with these things I doubt you could build your way out of a lego box let alone a pc.

    Have fun with your ignorance.
  • norbs
    hakestermanNorbs if you represent the few mindless linux supporters thani feel nothing but pitty for you. If Linux was anything in thisworld it would of bared some fruit by now. Instead it has shrunkto lower levels and will continue until nothing is left. You canfantasy all you want but it won't save Linux from its certain Death.
    Actually if you knew how many things out there ran linux in the background and that would not exist without linux u would probably not be talking so much.

    I use windows xp for my gaming machine, windows vista ultimate for my media center, and mac OSx (somewhat based on Unix) for my laptop hackintosh (it works thanks to it's linux based bootloader). I also work also for a hospital where 99% of our computers and servers are windows based. Sure MS has a huge share of computer, but maybe i;m a bit more well rounded and understand the benefits of every OS.

    My router is running DD-wrt (with VPN =] )which is linux based and it has some great features. Some Nas drives use linux. It's time to get your head out of your ass and stop hating things because you don't understand them. All OS's have their place... Go be a die hard fan of one thing it works out well for the company i really don't care...

    Maybe when you can afford more then your one computer that your play video games on and use for fighting on the internet you'll understand. In the mean time go sport your MS stuff. MS FOR LYFE!1!1!!!
  • fudgeboy
    lol well done to soul_keeper - i use Linux for my media center because windows was just too much of a resource whore!
    however for normal gaming etc i still look to windows.

    hakesterman - dogs have been in space. +1 to Soul_Keeper.
  • norbs
    fudgeboylol well done to soul_keeper - i use Linux for my media center because windows was just too much of a resource whore!however for normal gaming etc i still look to windows.hakesterman - dogs have been in space. +1 to Soul_Keeper.
    Hey fudge what distro do you use for your linux media center? I tried a couple and they were not impressive but it's been a while. I still want the eye candy that vista has with the menu transition.