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View Full Version : A shift to Serial.


manitoubalck
Sep 25, 2003, 09:51 AM
We are now seeing Serial ATA replacing the old IDE/Parallel ATA and the dawn of Serial PCI Express for graphics cards to replace the Parallel AGP standard. Serial Attached SCSI (SAS) is in the works and is looking to be released within the next 2-3 years, with transfer rates as high as 600MB/s, marketed at high-end servers etc.

USB 2.0, Firewire, Ethernet, V-Link, MuTIOL, HyperTransportģ, RapidIO are all serial-based, so it is safe to say that the computing industry is moving away from Parallel data transfer methods.
Why then are we still using DDR memory (current max clock on single channel 533MHz) when a Serial alternative has been around for 4 or so years? RDRAM or RAMBUS, was initially developed for use with the P4 and Xenon processors. It has single channel clock frequencies of 1600MHz, more than double that of the current fastest DDRRAM modules.

RAM makes computers work faster, and the faster the RAM and the more you have the more effectively it can use the Chipís FSB, hence the faster the computer can operate. Why not then have 8GB of RDRAM operating @ 1600MHz, rather than 4GB per channel operating @ 800MHz. I know RDRAM has suffered at the hands of a lack of consumer support due to itís high cost, but with widespread adoption as has occurred with DDR thereís no reason that this superior Serial product should fall by the wayside. Even the Specs of DDRII from JEDEC donít live up to those of RAMBUS.

The Shift is to Serial, so why should RAM be left behind when it is so critical to system performance.

stoid
Sep 25, 2003, 10:06 AM
BETA and VHS

MAC and PC

now

RDRAM and DDR


the first option is a bit more expensive (even though the quality is much greater) and so the general populous chooses the second. 'Tis the way of things.

tomf87
Sep 25, 2003, 10:34 AM
Most of the articles I've read show that DDR SDRAM gives you the same or greater performance versus RDRAM. Since RDRAM is much more expensive, why use it?

Intel learned this lesson, hence the reason they use DDR on their newer boards. Plus, since hard drives and PCI busses seem to be the bottleneck now, increasing RAM speed won't help that much. Now that PCI-X is external now, it's time that they modify on-board components to use these technologies.

Does anyone know of any documentation that states that onboard NIC's, audio, and ports on the faster G5's are actually on the PCI-X bus? Or are they going through a PCI bus and across a PCI-to-PCI-X bridge?

bousozoku
Sep 25, 2003, 12:10 PM
Originally posted by tomf87
Most of the articles I've read show that DDR SDRAM gives you the same or greater performance versus RDRAM. Since RDRAM is much more expensive, why use it?

Intel learned this lesson, hence the reason they use DDR on their newer boards. Plus, since hard drives and PCI busses seem to be the bottleneck now, increasing RAM speed won't help that much. Now that PCI-X is external now, it's time that they modify on-board components to use these technologies.

Does anyone know of any documentation that states that onboard NIC's, audio, and ports on the faster G5's are actually on the PCI-X bus? Or are they going through a PCI bus and across a PCI-to-PCI-X bridge?

You might want to check the technical notes at http://www.apple.com/developer for the G5.

Le Big Mac
Sep 25, 2003, 12:22 PM
Originally posted by manitoubalck

Why then are we still using DDR memory (current max clock on single channel 533MHz) when a Serial alternative has been around for 4 or so years? RDRAM or RAMBUS, was initially developed for use with the P4 and Xenon processors. It has single channel clock frequencies of 1600MHz, more than double that of the current fastest DDRRAM modules.



You might also look at the DRAM industry's regard for Rambus. Most of them aren't too pleased with Rambus's participation in JEDEC, the industry standard-setting organization. Or its subsequent efforts to strong-arm them on license agreements.

pellucidity
Sep 25, 2003, 03:50 PM
Unlike most of the other standards you mentioned, where the serial challenger replaced a wider-but-slower system, RD-RAM's latency and lower width mean that it's not easy for it to even compete with comparably priced DDR solutions. Then you consider that Rambus is not loved, and you have an answer. It's one thing for Apple to use a technology reserved for more expensive machines (SCSI), another for them to use a technology that has totally exited the mainstream... for a reason.

iPC
Sep 25, 2003, 03:53 PM
http://www.internetnews.com/bus-news/article.php/1369401

Yesterday, the FTC filed a case against Los Altos, Calif.-based Rambus, accusing it of deceiving the Joint Electron Device Engineering Council (JEDEC), a standards body, by not revealing its work on several pending patents that would allow it to effectively control standards JEDEC put in place. The FTC voted 5-0 to bring the charges, saying Rambus stood to gain $1 billion from the technology over its lifetime.Among other things. Not to mention that the price increase was not comensurate with performance increase.