Ok, this is what I've learned so far about EIDE: Many manufactures are selling IDE controllers labeled "Enhanced IDE". When in fact.. they're not! More like souped up standard IDE controllers. EIDE is a Western Digital trademark and must be licensed from WD to both comply with the standard and to have the EIDE logo. This logo roughly looks like a quarter of a circle with Enhanced written vertically and IDE written on the bottom. Originally, IDE was developed to replace the, then standard, ST-506 interface. Heres the history: ATA: The original IDE command set. Used in Mode 0-3. ATA2: Introduced in Mode 2. Its an extended command set used to communicate with IDE tape drives and CD-Roms. Mode 0: The original IDE that is now mostly gone. [ 16-bit ] MODE 1: A higher clocked IDE capable of BIOS compatibilty with larger HDs [ 16-bit ] Mode 2 Single Word: The common IDE controller today. Allows faster transfer rates on the AT Bus ( ISA ). For every software interupt, the drive would return ONE sector. [16-bit] Mode 2 Multi-Word: IDE that for every software HD interupt, the drive can return multiple sectors. This technology is enabled either in the motherboard's BIOS or a TSR given with the controller. The number of words returned is dependant on the hard drive. [16-bit] Mode 3: This is _true_ Enhanced IDE. This uses a feature called PIO. Programmable Input/Output allows the IDE data lines to be muliplexed to offer an effective 32-bit wide IDE bus. EIDE is defined to have a burst transfer rate of 13.3Mb/s with typical sustained transfer rates of 5 to 6 Mb/s. This is also Multi-word. [32-bit] Mode 4: Under construction but is to support 20Mb/s. The Western Digital Caviar line supports full multi-word, Mode 3, EIDE that supports up to 16 words per interupt. Another thing to note: MicroSoft Windows v3.1 and v3.11 has a serious flaw with Multi-word HDs. Drives such as Maxtor's, Quantums, SeaGates, etc fail to work correctly with Windows's 32-bit Disk access. However, Western Digital has written a driver for their Caviar line that makes ONLY caviar drives work in Multi-word mode with 32-bit disk access. Very important. Major selling point too! With a mode 3 controller.. your looking at SCSI-2 performance for a single user platform. The Sis-based motherboard has Multi-word support built into the BIOS. I also have a Multi-word controller that came with drivers for enabing the multi-word support. I didn't noticed any increase performace of using the drivers compared to the Sis BIOS supported multi-word support except the drivers took 40k of base memory!!! With the SIS motherboard, any cheap-o controller will give you Multi-word performace. Vesa-LocalBus controllers will give you a slight performace increase but not very much. Unless you need 16550 serial ports and all the wizz-bang features, getting a VLBus controller won't help you much. With a Vl-Bus IDE controller and a Mode 2 Multi-word motherboard, with a Western Digital 540MB drive, I'm getting about 2.2Mb/s sustained rates using Quantum's benchmark called Qbench ( recommened! ). EIDE controllers are now just starting to emerge on the market. For the limited research I've conducted, the going rate is about $60-$70. Typically these controllers support 2-16550 serial ports and a Enhanced Parallel port (EPP). Some controllers support 4 IDE drives where most support 2. Some controllers, such as the GSI 4C-VL, support ATA2, 4 hard drives, accelerated Floppy-based tape drive support, dual 16550 serial ports, an EPP parallel port for $169. Just a short list of manufactures are: CMD, GSI, Arco Elecctronics, Adaptec ( to be released ), Promise Technology, DTC, Boca, and Acculogic just to name a few. Experience: I bought a CMD controller and was VERY unhappy with it. The controller's drivers would always crash and the primary channel will only support upto 528MB drives. The second IDE channel does support large disks but the 2nd channel is a conciderably slower BUS. Also, the two serial ports are only 16250's and its manual sucks. So, to say the least, I don't recommend CMD. My $.02 worth.. +----------------------------------------------------------------------------+ | David A. Ranch [Computer Engineer] dranch@ecst.csuchico.edu | +---- ----+ +------- Linux 1.1.x Administrator ---- dranch@rocko.lab.csuchico.edu -------+