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Re: Some questions
- To: Mailing List Recipients <pci-sig-request@znyx.com>
- Subject: Re: Some questions
- From: "John R Pierce" <pierce@hogranch.com>
- Date: Wed, 4 Dec 1996 18:10:39 -0800
- Resent-Date: Wed, 4 Dec 1996 18:10:39 -0800
- Resent-From: pci-sig-request@znyx.com
- Resent-Message-Id: <"iXeTa.0.ph2.kzYfo"@dart>
- Resent-Sender: pci-sig-request@znyx.com
> I'm want to make several PCI cards for one project, but I have some doubts
yet:
>
> Why the amount of PCI slots are typically suggest as four ?
The spec allows for 10 bus loads, including bridges. Each connector counts as
2 loads due to the capacitance of the connector itself. Typical PCI system has
the host->PCI bridge, 4 slots, and the PCI->ISA bridge for a total of 10 loads.
> Can I put in the PCI bus eight cards ? this question is because I'll
> build the PCI bus on my project.
Not without violating these specs. You could have 8 onboard PCI devices (9 if
you don't need the PCI->ISA bridge). Or you could use a PCI->PCI bridge to add
more slots.
> Is possible to perform burst upon 1500 bytes in the PCI bus ? if it
> is possible then Can I do it in a ordinary PC ?
Um. Lets see, 1500 bytes is about 375 32-bit cycles. A bus master might be
able to. Most all PC (ie. pentium systems) won't generate burst reads, only
burst writes. There's no guarantee that you won't get a target retry abort
somewhere in the middle of that burst.
-jrp
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