Will the next Powerbook G4 have true DDR implementation?

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  • Reply 21 of 28
    Quote:

    Originally posted by Barto

    That's correct, and also COMPLETELY irrelevent to Apple's various G4 architectures.







    Believe me, that's totally obvious reading your post



    No CPU other than those with onboard memory controllers (eg POWERs, Athlon64s) ever sends and recieves directly to and from memory. In between the CPU and the memory is a northbridge (or system controller, or system intergrated circuit). The CPU makes requests to the northbridge for data from the memory, and the northbridge fetches the data from memory and sends it to the CPU.



    It IS true that less data can be sent to the G4 alone than can be fetched from memory, but it is NOT half. System busses aren't that simple, you can't just look at the MHz and make a judgment. The G4's bus is very efficient for it's speed, and DDR is highly inefficient.



    Now guess what. The Athlon is the same. The majority of Athlon computers in the world have a CPU bus slower than the memory bus. Guess what, PC user's don't call them "hacks" or "false". Do you know why? Because there's nothing wrong with asyncronous busses.



    But wait, there's more.



    In modern architectures, more and more devices have DMA. That's Direct Memory Access, the ability to ask for data from the memory, without going through the CPU. On the PowerBook, DMA devices include gigabit ethernet, the hard drive and most importantly the graphics chip. Using Quartz Extreme, the Radeon 9600 in the PowerBook G4 transfers buttloads of data from meory. So it's not JUST the CPU that consumes the memory bus, it's the networking, drives and graphics chip too.



    Barto




    Thanks for the post. A lot of consumers don't realize the RAM subsystem services more than the processor.



    As far as FSB goes, while it would be nice to have a faster FSB, you have to ask yourself why? What will it really do for me? On the 7455 Processors, for almost all Office Productivity tasks, the FSB speed is invisible. The instructions and size of the data being worked on is within the performance envelop of the FSB. The question is where does a higher FSB make sense. Well Video editing, complex graphics work, SIMD operations on huge data sets. You get the point. For most of us what is there is more than enough, though it would be nice to start at 400MHz FSB to future proof for Digital Lifestyle apps.



    But, one of the biggest problems with most computers is that they don't use what they got now. Software isn't developed very efficiently either. With simple techniques where Load operations are executed in parallel with Integer, FPU and SIMD instructions, a significant performance increase can be appreciated. Too, Apple continuing to optimize the GCC compiler, we are seeing significant performance increases with memory transfers as borne out by xBench with Panther compared to Jaguar.



    Using Quartz Extreme many of the Aqua operations no longer use the FSB for display operations, but do DMA from the GPU. So a lot of the OS work that can clog up the FSB has been offloaded to the GPU subsystem, like shading, moving, resizing, window drawing, transparencies, etc. Panther uses even more of the GPU for many of its operations than Jaguar.



    So what you have with Apples design is a better balanced system, were all the components are contributing to consistently good performance. The FSB will not be as bottleneck if less cars are driving down its road.



    There are other advantages to the Apple implementation of the FSB. It is a fully duplexed FSB, which means that a Load and a Store operation can be performed simultaneously. So 167 MHz in either direction which would consume the entire DDR bandwidth.
  • Reply 22 of 28
    Basically, my point is that it is not as grim as some make it out to be. The current FSB is more than enough and well balanced with the system it is on, especially when you include such other enhancements such as QE. Can it be better? Yes, it can always be better. It would be better in the Windows World as well if they had QE and a faster per clock CPU like the G4 as well as an orthogonal SIMD unit like Mac users have.



    If the G4 is not enough for you, Apple has the G5 which addresses all the FSB issues you can shake a stick at.
  • Reply 23 of 28
    Quote:

    Originally posted by KANE

    The difference between DDR RAM and SDR RAM can be read in the name: DDR = Double Data Rate (two instructions per Hz) / SDR = Single Data Rate (one instruction per Hz)



    Sorry to be nitpicky, but it's called "DDR SDRAM". as opposed to just plain "SDRAM", with the "SD" standing for "Synchronous Dynamic", not "Single Data".
  • Reply 24 of 28
    I thought benchmarks of the DDR PowerMac G4s showed it wasn't a real win over SDR. The primary advantage DDR has for Apple is that SDR is basically obsolete and will soon cost more (if it doesn't already).



    Also, Apple obviously thinks a fast system bus is important because the G5s have a incredibly fast bus.
  • Reply 25 of 28
    Quote:

    Originally posted by IntlHarvester

    I Also, Apple obviously thinks a fast system bus is important because the G5s have a incredibly fast bus.



    Of course a fast fsb is important in a workstation, that and it's "a good thing TM" for marketing.
  • Reply 26 of 28
    amorphamorph Posts: 7,112member
    Our front page just chimed in with the news that IBM is making the 750VX (the long-rumored "G3+Altivec") especially for Apple, and that it's in the final stages of development now.



    This is a likely candidate, because the 7457 is the end of the line for the Motorola G4. The 7457-RM got canned, and Motorola has only made noises about a "high-performance PowerPC" next year, which could be anything. Dual core offerings are an outside shot; RapidIO busses to memory controllers are a near lock, as is 90nm. The question, as always, is will Motorola be able to produce these things in any quantity, and in a timely fashion? If their experience with 90nm is anything like their experience with 130nm (and keep in mind, this time it's not their fab they're using, and they have help from Philips and STM) we won't see it for a good long time.



    So the IBM CPU is a good candidate for a replacement. Since the general description (G3 with longer pipelines and AltiVec) matches the current G4 closely, Apple's claims that the G4 has a roadmap with Apple can survive the jump across vendors and models.
  • Reply 27 of 28
    wizard69wizard69 Posts: 13,377member
    Well maybe it sounds grim because it is. Not so much from the perspective of todays machines, but form the perspective of stagnation in the laptop lines. Much as the MAC community has gone through this issue with the desktops in the past, the fear is that no growth is due for the laptop lines.



    On ething you did miss that can be an issue with bus bandwidth is all the fast serial ports now attached to a MAC. USB, Firewire, and gigabit ethernet can soak up a bit of that bandwidth. So while you are correct that Apple has attempted to balance system performance as best they can, and has done very well I might add, there can be problems with the current designs. Like all things it is question of how you use it, for many the systems are fine, but better performance does open up new opportunities.



    If there is a peception that the line has stagnated and those performance increase aren't to be seen then Apple will have a bit of a problem.



    Dave





    Quote:

    Originally posted by stingerman

    Basically, my point is that it is not as grim as some make it out to be. The current FSB is more than enough and well balanced with the system it is on, especially when you include such other enhancements such as QE. Can it be better? Yes, it can always be better. It would be better in the Windows World as well if they had QE and a faster per clock CPU like the G4 as well as an orthogonal SIMD unit like Mac users have.



    If the G4 is not enough for you, Apple has the G5 which addresses all the FSB issues you can shake a stick at.




  • Reply 28 of 28
    bartobarto Posts: 2,246member
    There's a Media Access Controller community? Huh?



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