Extract From Byte Magazine - April 30

[Steve Bildermann]

As BYTE is now a subscription service I thought some people might enjoy reading some extracts.

By Andy Patrizio

April 28, 2003

For the longest time, Intel was focused almost exclusively on the CPU and let other elements of the computer slide. The end result was modern CPUs with antiquated internals, creating the equivalent of a one lane highway with no speed limit. Sure, data could go fast, but there was no room to move.

Finally, Intel began to realize its mistake and set about working on the front-side bus, memory controller and channel and disk I/O. The CPU bus began to move up in speed, as did memory. Hard drives maxed out at 10,000 RPM and 7,200 not only became usable but a standard. Just a few years ago, a 7,200 RPM drive would be enough to turn your computer into a hotplate. Now they are cooler and more stable.

Thankfully, Intel held off until it had several innovations and put them all into one package, the 875P chipset, commonly called Canterwood. As Jerry has been raving in his column, it is indeed fast and a major improvement over previous chipsets.

The 875P is the replacement for the 850 chipset, which have been on the market for three years now, ancient in computer terms. The 865 chipset, called Springdale, will be the eventual 845 replacement. Springdale is a lower-end chipset for more affordable systems, while 875 is for performance/high end systems. More details on Springdale will come out in May, when it's officially released.

The 875P sports several notable features:

An 800 MHz system bus
Performance Acceleration Technology (PAT)
Dual channel DDR400 memory, together
Performance AGP 8X graphics interface
Gigabit Ethernet (GbE)
Dual independent Serial ATA ports and Hi-Speed USB 2.0 connectivity
The 800 MHz front-side bus is a major jump from the 533 MHz bus. The board is backwards-compatible with all 478-pin P4 chips.

The Performance Acceleration Technology, or PAT, is used to differentiate the 875P from the 865, another chipset that Intel is releasing, which is designed for low- to mid-range machines. PAT improves performance by optimizing memory access between the processor and system memory. It's only on the 875P, however; the 865 won't have it.

Dual channel memory means you can access two memory banks at once, effectively doubling the bandwidth for memory. The memory of choice is Dual Data Rate (DDR) SDRAM, consigning RDRAM to the ashcan. There wasn't a problem with RDRAM, it's just that there are so many more SDRAM vendors; the memory is cheaper. With 400 MHz memory (sold as PC3200 memory) and the 800 MHz front-side bus, you get a maximum of 6.4 GB/s of bandwidth between the processor, memory and system controllers: twice what it used to be in older P4 systems.

However, memory management in the 875P system is a bit trickier, and you have to be careful.

The motherboard comes with four DIMM sockets, and DIMMs must be installed in pairs.
Each DIMM in a pair must be the same size. You can't put a 128MB DIMM in one socket and a 256MB in another.
Both DIMMs must use the same density memory chips.
Each DIMM use the same DRAM bus width (8x or 16x)
Each DIMM must be either single-sided or dual-sided, you cannot mix a single and a dual sided DIMM in a pair.
If you violate these rules, the motherboard defaults to single-channel mode, or it may lock up, depending on how the motherboard manufacturer wants to enforce this. In Intel's case, it falls back to slower performance.

Also onboard is Gigabit Ethernet, a big upgrade for the old network controller, at least in some environments. For those of us at home with DSL/cable modems, you won't notice the least bit of difference due to limitations on the DSL/cable modem. But if you have a high-speed LAN or Internet connection at work, then it will make a difference. Like Jerry, I had nothing but trouble with the onboard controller and drivers, and ended up using an old 100 Mbit controller card.

Finally, there's Serial ATA. If there's a more detested PC component than the wide, 80-pin ATA ribbon cable, I don't know what it is. They are a major pain to work with, like trying to snake around in the computer and get into place. Not just that, but ATA is over a decade old and performance was really starting to lag. So Intel and its hardware partners set out fixing the problem.

The solution was Serial ATA. The transfer rate starts out at 150 MB/sec, only slightly faster than the 133 MB/sec maximum speed of parallel ATA, although it's safe to say those old hard drives and controllers rarely if ever came close to that 133 MB transfer rate. More importantly, SATA will scale up to 300 MB/sec with the next generation and to 600 MB/sec after that.

The big benefit to SATA aside from performance is its cable. The cable connecting the drive to the motherboard can best be compared to the cable that connects a CD-ROM drive to an audio controller so you can listen to music, although it's a little thicker. It bends easily to tuck away in the case. Laptop makers will rejoice when they get to use this.

Intel sent me a pair of Seagate Barracuda 120 GB SATA drives, and the Intel 875PBZ motherboard supports RAID0 (more in a minute). Hooking up the drives was simplicity, because there's only one way to hook up the cable. It's not like regular ATA where you can hook up the cable upside down.

In fact, there is a slight problem with SATA that caught my eye immediately: The cable can come out just by blowing on it. As much of a pain that legacy ATA could be, once you plugged it in, it stayed in. These SATA cables fall out way too easily. How could they allow this to happen?

The motherboard also came with regular ATA controllers for the CD-ROM drives as well as a floppy controller, so the legacy equipment is preserved. Eventually all ATAPI drives will support SATA and parallel ATA can go by way of the ISA slot, but that will be a while. For the next few years, motherboards will come with both controllers.

RAID0 allows you to merge several drives into a single image. So with RAID0 enabled, my two 120 GB drives have become one massive 240 GB drive. This sounds nice, but remember one thing: You double your chances at losing everything. If one of the drives goes bad, the whole system is lost since it's seen as a single image, so two drives means twice the chance of failure.

With the new 3.06 GHz 875P system built, it was time for a head-to-head battle with my existing 3.06 GHz system, which ran RDRAM and the 850 chipset. Here are the vitals:

Old system
Pentium 4 3.06 GHz
Intel D850EMV2 motherboard
512MB PC1066 RDRAM (533MHz)
80GB 7,200 RPM ATA drive
GeForce 3 video

New system
Pentium 4 3.06 GHz
Intel D875PBZ motherboard
512MB PC3200 SDRAM
240GB 7,200 RPM Serial ATA drives (RAID0)
GeForce 4 video

The video cards were irrelevant because I wasn't looking at the video performance, plus, the AGP video in the 850 motherboard is 4x while the 875 has 8x AGP, so it would not be a fair comparison. Both systems run Windows XP Home Edition.

Serial ATA Legacy ATA SATA Difference
Boot time (seconds) 15 29 51.7%
SANDRA disk (kb/sec) 41,161 17,109 240.6%
SANDRA memory (MB/sec) 4,712 3,321 141.9%
DiskSpeed 32 (kb/sec) 65,532 21,831 300.2%
PCMark 03 CPU 7,738 7,405 104.5%
PCMark 03 memory 8,861 6,108 145.1%
PCMark 03 disk 1,190 625 190.4%


The numbers don't lie, and neither do I. In all three areas of performance—CPU, memory and disk—the 875 clobbers the 850 when using the same speed CPU. The improved controller technology makes the CPU slightly faster, there's the dual channel memory and increased speed, and nothing more needs to be said about serial ATA. The boot time is from POST until the Windows XP music chimes and you have access to the desktop.

The price tag is a bit steep. Intel estimates the motherboard will sell for $170 to $180, a bit more than the usual price, but that's because of the RAID and Gigabit Ethernet. Third-party motherboard vendors may skip both features and sell them for a lot less, like around $120 or so.

Also, the Barracuda drive is around $179, which is up there. Fortunately, the memory is cheap. PC3200 memory is around $49 for a 256 MB DIMM, and several vendors (Kingston, Corsair) already have certified memory DIMMs ready to go for the 875.

In all things, the 875P is a major improvement over its predecessors and worth the upgrade. It will cost you a little more, but not all that much. As third-party boards from Asus, Abit and others come on the market without the bells and whistles like RAID, then the price will come down, as will SATA drives.