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Date:      Wed, 18 Nov 1998 18:54:04 +0000
From:      "Luis Guerra e Silva" <lgs@vinci.inesc.pt>
To:        Carlos Frazao <frazao@itqb.unl.pt>
Cc:        aic7xxx@FreeBSD.ORG
Subject:   Re: Problem with AIC-7895
Message-ID:  <9811181854.ZM26647@kepler.inesc.pt>
In-Reply-To: Carlos Frazao <frazao@itqb.unl.pt> "Re: Problem with AIC-7895" (Nov 18,  4:43pm)
References:  <199811181643.AA09544@brutus.itqb.unl.pt>

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Since there's many people having some problems with the Tyan
Thunder II board, here is a tip.

I had some problems with my Tyan Thunder 2 motherboard, and
I contacted the technical support. From what they told me, I can
deduce that there is a version of this motherboard that has the
IRQs of both channels hardwired (read technical support answer, below).
This means that you can only put channel B to work if it uses the same
IRQ as channel A. In Linux it might work with the 7895_irq_hack, but in
Windoze 95 it doesn't work at all, because the Adaptec drivers don't
support using the same IRQ for both channels. However, in Linux if you
don't use the 7895_irq_hack it will hang during the boot, when
scanning for devices in channel B.

Good, luck !
-Luis

Here goes my e-mail to the technical support and the answer.

My E-Mail
----------------------------------------------------------------------

Hello !

A year ago (in the Christmas) I bought a Tyan Thunder II board (1696DLUAN).
I'm using SCSI disks with its onboard aic7895-based SCSI controlller.
Until today I was only using channel A, but I bought a new disk and
I've tried to use channel B in Windows 95, but it doesn't work.
I think I known the cause of this problem, but I don't know the
solution (I hope you do ;-).

After buying the board I tried to install Linux, but since there was
no Linux driver for the aic7895 at that time, I e-mailed the Linux
aic7xxx driver developer (Doug Ledford) and asked him about the
availability of this driver. Later, he sent me some beta versions for
testing and during the test procedure we discovered that channel B wasn't
responding correctly (the boot sequence was hanging when scanning for
channel B). After this we discovered that the IRQs of both channels where
somehow "hardwired", and that the only way to put channel B to work was using
the interrupt of channel A (currently the Linux aic7xxx driver has a
switch called 7895_irq_hack specific for the Tyan Thunder II "buggy" board).
He also told me that the SCSI controlled didn't had a SEEPROM (?).

Until today I was living happy with my "buggy" motherboard, because
I was only using channel A. But now I need to use both channels and
the things are getting complicated. In Linux I can use both channels
due to the hack I described (though I'm not very happy knowing that
both channels are using the same IRQ, since it reduces the I/O
performance). But in Windows 95, I'm stuck because when I try to
boot with each channel using a different IRQ it hangs, and when I
try to manually configure the same IRQ for both channels it also
hangs (the Windows driver documentation says that for multi-channel
adapters it doesn't support the same IRQ assigned to both channels).
For Windows 95 to boot properly I must disable channel B.

So my question is quite simple: How can I put each channel of the
SCSI controller to work with a different IRQ, both in Linux and
Windows 95 ?

(You are going to tell me that you don't support Linux, but since I
think this is a motherboard hardware/bios problem, once it is solved
for Windows 95 it will also probably be solved for Linux.)

Thank you for your time. I'm waiting for an answer ASAP.


Tyan's Technical Support answer
------------------------------------------------

> Luis,
>         A couple things.  One is that sharing the same IRQ between SCSI
> channels A and B works fine in our tests.  And second, boards shipped
> last year when you got yours did have Channels A and B using separate
> IRQs so your board should still be fine.  So maybe there is something
> else going on here.  Anyway if you feel your board may be defective,
> you may want to send it to us and we can take a look at it.
>
> Don


-- 
*** Linux: The Choice of a GNU Generation. ***

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