Date: Thu, 23 Jan 1997 12:03:20 -0500 From: John Duncan <jddst19+@pitt.edu> To: Nadav Eiron <nadav@barcode.co.il> Cc: Jen and Luke <isis@servtech.com>, "questions@FreeBSD.ORG" <questions@FreeBSD.ORG> Subject: RE: EIDE drives Message-ID: <01BC0927.31C06C40@ehdup-i-2.rmt.net.pitt.edu>
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---------- From: Doug White[SMTP:dwhite@gdi.uoregon.edu] Sent: Wednesday, January 22, 1997 10:56 AM To: Nadav Eiron Cc: Jen and Luke; questions@FreeBSD.ORG Subject: Re: EIDE drives Here I go trying to understand the difference between EIDE and IDE and screw it up massively. :-) Will someone please fill me in? I don't consider a difference between the two. ---- What I gather on the subject: First and foremost, the ide/eide/ata/ata-2 specifications only truly became specified with ata, and nobody felt the need to follow the specification exactly. Before the ata-2 standard came out, there were vlb card manufacturers and drive makers who wanted to provide a 32-bit bus and a couple of higher clock rates to the drives, so they could write "32-bit" on their boxes, and people would buy them. FreeBSD supports some of these features, such as 32-bit pio multi-block transfers, and the ability to select in the kernel-config whether we want to use these features, and how much we want to transfer. What we don't seem to provide is the selectable clock-rates for the drives. My promise bios starts drives automatically at speed 2, and then the win95 driver steps this speed up to the reccommended setting (or user-defined setting) for the drive. The driver claims, although my drives are old enough to not support it, that the speed can be selected from 0 to 8 (I don't know the relations off-hand) and that the speed can also be selected per the ATA spec. (This, sadly, I also cannot test.) There is actually only a small set of "EIDE" enhanced st506 drivers out for us, so if we just collected the data for them (the air force has a good listing), we should be able to write a config option that loads the correct bits. -John
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