Re: C3600, sata controller

[John David Anglin <dave.anglin@bell.net>]

On 2019-05-13 7:47 p.m., Carlo Pisani wrote:
> So levels should be compatible, but so what is the difference between
> 64-bit PCI slot and PCI-X slot?
There is no difference in the slots except PCI-X slots are always 3.3V and a 5V card won't work in them.
The difference is in the bus protocol and timing.

This is what I see in wikipedia:

"In PCI, a transaction that cannot be completed immediately is postponed by either the target or the initiator issuing retry-cycles, during
which no other agents can use the PCI bus. Since PCI lacks a split-response mechanism to permit the target to return data at a later time, the
bus remains occupied by the target issuing retry-cycles until the read data is ready. In PCI-X, after the master issues the request, it
disconnects from the PCI bus, allowing other agents to use the bus. The split-response containing the requested data is generated only when the
target is ready to return all of the requested data. Split-responses increase bus efficiency by eliminating retry-cycles, during which no data
can be transferred across the bus.

PCI also suffered from the relative scarcity of unique interrupt lines. With only 4 interrupt lines (INTA/B/C/D), systems with many PCI devices
require multiple functions to share an interrupt line, complicating host-side interrupt-handling. PCI-X added Message Signaled Interrupts
<https://en.wikipedia.org/wiki/Message_Signaled_Interrupts>, an interrupt system using writes to host-memory. In MSI-mode, the function's
interrupt is not signaled by asserting an INTx line. Instead, the function performs a memory-write to a system-configured region in host-memory.
Since the content and address are configured on a per-function basis, MSI-mode interrupts are dedicated instead of shared. A PCI-X system allows
both MSI-mode interrupts and legacy INTx interrupts to be used simultaneously (though not by the same function.)

The lack of registered I/Os limited PCI to a maximum frequency of 66 MHz. PCI-X I/Os are registered to the PCI clock, usually through means of a
PLL to actively control I/O delay the bus pins. The improvement in setup time allows an increase in frequency to 133 MHz."

Nominally, one would think a PCI-X card would fall back to PCI mode but maybe this needs firmware
support.

I still think the 3.3V signalling of a PCI-X card likely is incompatible with 5V signalling in c3600.  A 5V
card won't work in a PCI-X slot.  Only slot SL2 is 3.3V.

Wiki also says:

"Many 64-bit PCI-X cards are designed to work in 32-bit mode if inserted in shorter 32-bit connectors, with some loss of speed.[19][20] An
example of this is the Adaptec 29160 64-bit SCSI interface card.[21] However some 64-bit PCI-X cards do not work in standard 32-bit PCI slots.[22]"

So, I think you can only use 5V or universal conventional PCI cards in c3600 (except for slot SL2).

Here are some Adaptec 64-bit cards that I found.
https://storage.microsemi.com/en-us/support/raid/sata/aar-2410sa/
https://storage.microsemi.com/en-us/support/raid/sata/aar-21610sa/

Dave
-- 

John David Anglin  dave.anglin@bell.net