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Date:      Mon, 10 Jan 2000 00:24:57 -0500
From:      "Allen Pulsifer" <pulsifer@mediaone.net>
To:        "Gustavo V G C Rios" <grios@ddsecurity.com.br>
Cc:        "freebsd-questions@FreeBSD. ORG" <freebsd-questions@FreeBSD.ORG>
Subject:   RE: hardware
Message-ID:  <NBBBJNDFEKPEHPFCLNLHEEFAFCAA.pulsifer@mediaone.net>
In-Reply-To: <387960EC.F001C568@ddsecurity.com.br>

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According to the PCI spec, a PCI slot can be any of the following:

a) 32 bits / 33 MHz     c) 64 bits / 33 MHz
b) 32 bits / 66 MHz     d) 64 bits / 66 MHz

Any card can be plugged into any slot (subject to the
voltage and power requirements, discussed below), but:

- A 64 bit card plugged into a 32 slot only does 32 bit transfers.
- A 66 MHz card plugged into a 33 MHz slot operates at 33 MHz.
- A 32 bit card always does 32 bit transfers, even in a 64 bit slot.
- A 33 MHz card plugged into a 66 MHz slot slows the entire bus down
  to 33 MHz, and all cards plugged into that bus operate at 33 MHz.

There two issues with voltage requirements:

1) A PCI bus can have a 3.3 V or a 5.0 V signalling environment.
The card must support the signalling environment used by the bus.

2) A PCI bus can provide 3.3 V power, or 5.0 V power, or both.
A PCI card may be able to run off either voltage, or it may
require a specific voltage.

The ultimate high end PCI card will support 64 bits, 64 MHz,
either 3.3 V or 5.0 V signalling, and work with either
3.3 V or 5.0 V power.  It can be plugged into any PCI slot
and will make the best possible use of the slot.  I believe
the network and SCSI cards you are looking at fit this description.

64 bits at 66 MHz provides the highest bandwidth, but you may have
enough bandwidth even if you can only operate the card at
32 bits 66 MHz.

I believe Intel has motherboards that support 66 MHz,
but it does not make any motherboards that support 64 bits.
They use a bridge chip that converts the AGP port into
a 66 MHz PCI bus.

Intel makes one chipset that supports 64 bits, called the
450NX, and you may find third party Pentium motherboards
that use this chipset.

Micron also makes their own chipset.  I don't remember its
capabilities, but check out their web site.

No one else (VIA, SIS, etc.), as far as I know, makes a PC chipset
that supports either 64 bits or 66 MHz.

However, Compaq/Digital supports 64 bits/66 MHz in their Alpha servers.

Finally, if you can afford to wait, Intel's new chipset, the
840, is very flexible and you may soon see it in motherboards
that support both 64 bits and 66 MHz.

Allen


> -----Original Message-----
> From: owner-freebsd-questions@FreeBSD.ORG
> [mailto:owner-freebsd-questions@FreeBSD.ORG]On Behalf Of Gustavo V G C
> Rios
> Sent: Sunday, January 09, 2000 11:33 PM
> To: rene@tp98.catv.szabinet.hu; questions@FreeBSD.ORG
> Subject: Re: hardware
> 
> 
> Rene Scott wrote:
> > 
> > On Jan 9 Gustavo V G C Rios wrote:
> > 
> > > I am seeking a motherboard with 64 bit PCI slot, but i see no asus with
> > > such a configuration, can anyone here suggest me some another?
> > >
> > Yes, but not with FreeBSD...
> > http://www.sun.com/servers/workgroup/2/spec.html
> > 
> > I don't know of any i386 board w/64bit PCI slots.
> > Check out the Intel L440GX+ at
> > http://developer.intel.com/design/servers/l440gx/prodspec.htm
> > This is a really good MB.
> > 
> > Later,
> >         Rene
> 
> 
> Now, i really got confused, AHA-3950U2 requires 64-bit PCI slot
> See: http://www.adaptec.com/products/overview/scsi3950u2.html
> 
> Another: ANA 62044 Four-Port, 64-Bit PCI Network Interface Card for
> Fast Ethernet Environments 
> 
> See: http://www.adaptec.com/products/overview/quartet64.html
> 
> 
> -- 
> The reasonable man adapts himself to the world; the unreasonable one
> persists in trying to adapt the world to himself.  Therefore all
> progress depends on the unreasonable man.
>                 -- George Bernard Shaw
> 
> 
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