Re: Adaptec scsi driver OBSD 3.3 question

["J.D. Bronson" <jeff@xpec.com>]

At 11:53 AM 05/03/2003, Marco Peereboom wrote:
>2-5 seconds? Let's think about that.
>
>Let's say our hypothetical SCSI card has a single drive attached to it.
>
>According to the spec a Selection Time Out (STO) asserts busy for at
>least 250ms. An STO happens when the initiator asserts BUSY, SELECT and
>ATTENTION with an unused target id. This happens for example when the OS
>issues an INQUIRY command to ALL target ID's during boot. So in our
>little example we have 1 drive and thus 14 STO's. That makes it roughly
>3.5 seconds.
>An INQUIRY is an "expensive" command because the drive needs to collect
>a whole bunch of data. In normal circumstances the drive will disconnect
>from the bus; collect the data; reconnect to the initiator and return
>the data. Depending on the drive this can take up to a few hundred mili
>seconds (the newer U320 models can really take a while). This also
>assumes that everything actually is functioning as it should. So just
>executing the scan takes lets say 4 seconds. With your numbers you only
>have a 1 second window of opportunity for something to get corrected.
>That is not a whole lot in SCSI land where smart devices go off and "do
>something". This assumes also no LUN support and does not mention all
>the OS administrative commands it issues during boot(READ CAPICITY,
>READ(10) etc).
>
>Attached is a SCSI trace of me powering on a box with a drive attached
>to a SCSI card.
>You'll see several INQUIRY's (0x12) but only the last one in the
>sequence is relevant for this discussion. (ok, so I powered up the box
>and went into the BIOS; regular POST causes all kinds of crap on the
>bus). This is also a very old drive (I believe 95-ish) that does not
>take as long on an INQUIRY as newer ones. It is interesting to note that
>a STO takes quite a bit longer than 250ms because of setup time and bus
>free time.

WOW! that was more info than I ever expected :)
Ok...so I leave that value alone....but what about
AHC_ALLOW_MEMIO ?

Just for a test, I added that into myconfig file for kernel
build as:

option    AHC_ALLOW_MEMIO

...the kernel built and I did see it going by during the build process.
So am I to assume it is now active?

The machine booted just fine.

is there a command I can do to see if it is using MEM IO now? (presuming I 
did this right in the first place)








-- 
J.D. Bronson
Aurora Health Care
Information Services
Milwaukee, Wisconsin USA
Main Office: 414.978.3000