Chipset features compared
Here you can compare most of the major features of the most common Pentium 4 chipsets on the market. Our goal in compiling this table: to make your head explode. Please read intently.

Intel 845PE Intel 845GE Intel 850E Intel E7205 Intel 865PE Intel 865G Intel 875P SiS 648 SiS 648FX SiS 655 SiS R658 VIA P4X400 VIA PT800
Max. bus speed 533MHz 533MHz 533MHz 533MHz 800MHz 800MHz 800MHz 533MHz 800MHz 533MHz 533MHz 533MHz 800MHz
Memory type DDR DDR RDRAM DDR DDR DDR DDR DDR DDR DDR RDRAM DDR DDR
Max. effective memory clock speed 333MHz 333MHz 1066MHz 266MHz 400MHz 400MHz 400MHz 333MHz
(400MHz unofficial)		 400MHz 333MHz
(400MHz unofficial)		 1066MHz 333MHz
(400MHz unofficial)		 400MHz
Memory bus width 64 bits 64 bits 2 x 16 bits 2 x 64 bits 2 x 64 bits 2 x 64 bits 2 x 64 bits 64 bits 64 bits 2 x 64 bits 2 x 16 bits 64 bits 64 bits
Peak theoretical memory bandwidth 2.7GB/s 2.7GB/s 4.2GB/s 4.2GB/s 6.4GB/s 6.4GB/s 6.4GB/s 2.7GB/s
(3.2GB/s)		 3.2GB/s 5.4GB/s
(6.4GB/s)		 4.2GB/s 2.7GB/s
(3.2GB/s)		 3.2GB/s
Maximum addressable RAM 2GB 2GB 2GB 4GB 4GB 4GB 4GB 3GB 3GB 4GB 4GB 3GB 3GB
Max. AGP mode 4X 4X 4X 8X 8X 8X 8X 8X 8X 8X 8X 8X 8X
North/south bridge interconnect Accelerated Hub Accelerated Hub Accelerated Hub Accelerated Hub Accelerated Hub Accelerated Hub Accelerated Hub MuTIOL MuTIOL MuTIOL MuTIOL V-Link V-Link
Interconnect clock speed 266MHz 266MHz 266MHz 266MHz 266MHz 266MHz 266MHz 533MHz 533MHz 533MHz 533MHz 533MHz 533MHz
Interconnect bus width 8 bits 8 bits 8 bits 8 bits 8 bits 8 bits 8 bits 16 bits 16 bits 16 bits 16 bits 8 bits 16 bits
Peak theoretical interconnect bandwidth 266MB/s 266MB/s 266MB/s 266MB/s 266MB/s 266MB/s 266MB/s 1.06GB/s 1.06GB/s 1.06GB/s 1.06GB/s 533MB/s 1.06GB/s
Disk interface support up to... ATA/100 ATA/100 ATA/100 ATA/100, Serial ATA 150 ATA/100, Serial ATA 150 ATA/100, Serial ATA 150 ATA/100, Serial ATA 150 ATA/133 ATA/133 ATA/133 ATA/133 ATA/133 ATA/133, Serial ATA 150
USB mode support 2.0 2.0 1.1 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0
USB controllers/ports 3/6 3/6 2/4 4/8 4/8 4/8 4/8 3/6 3/6 3/6 3/6 3/6 4/8
IEEE 1394 controllers/ports 0/0 0/0 0/0 0/0 0/0 0/0 0/0 2/6 2/6 2/6 2/6 0/0 0/0
AC97 audio channels 6 6 6 6 6 6 6 6 6 6 6 6 6
Network interfaces 10/100Mbps Ethernet 10/100Mbps Ethernet 10/100Mbps Ethernet 10/100Mbps Ethernet CSA CSA CSA 10/100Mbps Ethernet
1/10Mbps HPNA		 10/100Mbps Ethernet
1/10Mbps HPNA		 10/100Mbps Ethernet
1/10Mbps HPNA		 10/100Mbps Ethernet
1/10Mbps HPNA		 10/100Mbps Ethernet 10/100Mbps Ethernet

Feature-wise, the 648FX and PT800 are largely on par with Intel's 865/875 chipsets. Yes, the 648FX lacks true Serial ATA, and both of these chipsets have single-channel memory controllers, but that's about it.

I should, however, point out one significant design difference between the Intel chipsets and those from VIA and SiS. The Intel north and south bridges are connected by only a 266MB/s link, while the PT800 and 648FX both have 1GB/s of chip-to-chip bandwidth. That's a major difference, and as you might imagine, the Intel chipsets have a real liability there. Intel has attempted to alleviate some of the strain on this interconnect by incorporating its "CSA" interface for Gigabit Ethernet chips right on the north bridge. That move will help, but it's not entirely sufficient. VIA and SiS have the advantage in I/O bandwidth.