E-Commerce Times Talkback
See Full Story
This week, Steve Jobs presented Apple's latest high-end computer systems, driven by the IBM PowerPC 970 processor and branded by Apple as the G5. The hardware adds up to what Apple claims is the fastest desktop computer, leading Jobs to quip, "Pretty cool, huh?" But there is a little bit missing -- 32 bits, actually. Jobs made much of the fact that the G5 Power Macs will be the first 64-bit desktop systems. Of course, that capability requires support from the operating system -- and there was no mention of when OS X will offer full 64-bit support.
The author seems to be confused about the difference between a "process" and a "processor."
I interpret the quotation below to mean that even a single-processor G5 system can use 8GB of RAM, it just can't allocate more that 4GB to a single process. So no 5GB databases in RAM (unless one does something tricky with inter-process communication) but saying "it's not the same as having each processor access 8 GB" is either misleading or flat-out wrong, depending on your point of view.
-------- below this line is a quotation --------
But it also says just below that, "Mac OS X takes full advantage of the 8 GB memory capacity of the Power Mac G5: It can now allocate up to 4 GB of memory per process to easily fit memory-intensive applications into RAM."
Now, using two separate processors to access that 8 GB of memory is impressive, but it's not the same as having each processor access 8 GB.
try to use a mac every day and be sure you'll switch.
in french : article sans fondement; pure jalousie.
J'espère que bill tremble et se mord les doigts d'être à la
tête d'une entreprise aussi peut innovante; ne misant que sur la standardisation............
vive la france, vive APPLE.
[quote]What's unusual is the 128-bit double data rate synchronous DRAM (SDRAM) connection to that memory, allowing a total of 6.4 GB of memory streaming to the processor(s) per second. That is comparable to what Intel puts into its high-end 875p chipset, but Intel does it with two 64-bit chips, called "dual channel," so the Apple configuration appears a bit unusual.[/quote]
Actually, there is nothing unusual with the way Apple made its memory controller chip. The Intel chip-set is composed of the Intel 82875P which can either communicate with one channel (64bits) or dual channel (128bits). Same as the Apple chipset. In fact, both have AGP 8x in the memory controller chip, as well as the processor interface. In Apple's case, there are two independent processor interfaces; one for each processor, instead of one shared processor interface in Intel's case (2 or more processors would need to share the one processor interface).
The other half of the 875P chipset is the 82801EB ICH5 chip. There is a corresponding chip for the new PowerMac G5 as well. That's the chip marked #7 on the diagram in Apple's web page at http://www.apple.com/powermac/architecture.html. What you lose with the Intel chipset is a way to do PCI-X.
As far as 64 bits and your claim of missing 32 bits, true, a process might be limited to accessing only 4GB (2^32) locations in memory, but addressing is only part of it. The other part, the more substantial, is how the new processor internally manipulates the data. It represents it in 64bit pieces (with software), and can potentially do twice as much as a 32bit processor. Also, on a single processor system with 8GB of memory, it could be running two processes, each of which is accessing its own 4GB of memory, with virtual memory, you are not limited to 2 processes.
I think that you need to do a little bit more research prior to submitting your article. With the advent of the internet, people can check and hopefully help in corrections for articles.
There's actually a difference in the way the dual-channel DDR is supported in the Apple memory controller versus the way it's done in the Intel 82875. I agree with you that "unusual" is perhaps too strong a word. I appreciate your comments about the strengths of 64-bit registers in the G5, though what is "substantial" in any product will depend on what you're trying to do. If you want >4 GB memory support for each processor, then the lack of such in the shipping G5 system will be a "substantial" lack. Regardless, the point is that a computer in which any one processor is not enabled to address more than 4 GB of memory is not a 64-bit computer by general definition.
Actually, I'd like for you to elaborate on what is "unusual"? .
I've gone through the Intel 875P data sheet, and Intel's part has a drawback that the Apple chip doesn't. Intel's chip only supports 2 DIMMs per channel. For a dual channel system, that's 4 DIMMs. The Apple system has provisions for 8 DIMMs on the dual processor configuration. An Intel 875P on any system is limited to 4 DIMMs.
I contend that there is nothing unusual with the 128bit DDR SDRAM connection used by Apple. It's similar to the way Intel implemented their design as well, with ONE chip doing the memory controller aspect of the chipset. The second chip mentioned, the IO controller does not have any memory controller functions. I do not see the 'unusualness'. The difference between Intel and Apple is that Intel allows you to use one channel or two channels, whereas we only know that Apple uses the full 128bits. We do not know if Apple implemented their chip as one channel/two channel, or if it's just one large 128bit wide channel.
As far as the >4 GB memory support, its SMoF, or Simple Matter of Software. I'm sure that this is just a temporary limitation of the OS, that is probably being fixed as we speak (figuratively). What is important is that the hardware is not hampered at being less than 4GB for ALL TIME, since that is the part that is immutable. Software can be revised and reinstalled after the fact. Hardware cannot, without difficulty.
Would you contend that when the first 80386 32-bit chips started shipping in computers, and Windows was still in version 3.x (16-bit) and not Windows 98, that these computers were 16 bit computers?