Date: Sat, 26 Jun 1999 11:35:02 +0100 From: Karl Pielorz <kpielorz@tdx.co.uk> To: Eric Jacoboni <jaco@titine.fr.eu.org> Cc: freebsd-questions@FreeBSD.ORG Subject: Re: IDE DMA and 'multi-block' Message-ID: <3774ACD6.3D02F00D@tdx.co.uk> References: <19990625221342.815A615669@titine.fr.eu.org>
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Eric Jacoboni wrote: > I've noticed something i don't explain about my 2 IDE disks : > wdc0: unit 0 (wd0): <QUANTUM FIREBALL1280A>, DMA, 32-bit, multi-block-8 > wdc0: unit 1 (wd1): <QUANTUM FIREBALL_TM2550A>, DMA, 32-bit, multi-block-16 > > Ok, both disks are in DMA 32 bit mode, but why the first one is said > 'multi-block-8' and the second 'multi-block-16' ? > > As i've understood the docs, the flags '0xa0ffa0ff' mean : > > - 0xa0ff for wd0 : probe 32 bit transfers + probe PCI IDE DMA + max > transfer size > - 0xa0ff for wd1 : same thing... > > Both drives are Quantum FireBall IDE disks, the first one is a 1.2 Go, > while the second one is a 2.5 Go : is it this size difference that > explains the 'multi-block' difference ? The number of multi-blocks supported will vary between drives depending on their age, spec, vendor - and even firmware that their running... The smaller/cheaper drives tend to do less, though it's quite common these days for even the cheapest/smallest to do high multi-block transfers... > BTW : what is the real meaning of this 'multi-block' value and what > are its implications ? AFAIK It's the number of blocks that can be transferred in one i/o operation, generally - the more the merrier... -Kp To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-questions" in the body of the message
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