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The Extended Industry Standard Architecture (EISA) is designed to support 32-bit expansion boards. With the speed of processors increasing almost overnight, the desire to take full advantage of this power has fed demand for 32-bit expansion boards in high-end network file servers. This comparison looks at five 32-bit Ethernet network interface cards for EISA machines running NetWare. We used a Compaq SystemPro LT as our test platform.
Three of the five cards employ bus-mastering techniques, in which a card's on-board controller relieves the server CPU of some data processing tasks. Eagle Technology's NE 3200 and BusTek Corp.'s BT-760A use on-board processors (Intel 80186 running at 10 MHz for Novell and at 16 MHz for BusTek). Standard Microsystems Corp.'s EtherCard Plus Elite 32T board offers bus mastering without an on-board processor. Instead, it contains two intelligent Ethernet controllers, letting you run two segments from one card. Of the two nonbus-mastering cards, Mylex Corp.'s LNE390 uses a shared memory architecture, and Racal-Datacom Inc.'s ES3210 can use either direct memory access (DMA) "slave" or shared memory architectures.
All five boards in this comparison ship with server drivers for the Novell NetWare 386, Version 3.11 operating system and related EISA configuration files. Most vendors either offer or are working on additional drivers for Unix and NDIS.
ALTERNATIVE APPROACHES TO 32-BIT EISA CARDS. The cards in this companson are designed for the high-end file server with multiple Ethernet segments attached. The Ethernet controller handles data transfer between the host system and the physical layer, which has a fixed maximum data rate of 10 megabits per second (802.3 specification). The host interface has three main approaches for Ethernet controllers: shared memory, DMA slave, and bus mastering. Each approach has advantages and disadvantages that are important to consider for optimum system performance.
The shared memory architecture uses dual-ported RAM as a buffer between the system bus and the LAN controller. This dual port allows the system bus to access system memory through one port, while the Ethernet controller accesses memory through the other port--thus the term "shared memory." Through this design all of the network traffic is localized on a dedicated bus with little effect on the system bus.
The main advantage to this approach is a low-cost, simple design that...