Help - questions on PCI-X and PCI Express

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L

L

Hi,

I have a couple of questions on the PCI-X and PCI Express, and would
appreciate it if some one could help.

Most 1U servers let people install up to 2 PCI cards. For some reason, we
need to install 3 PCI cards in a 1U server, which normaly is very hard.
Since we just need 1 HDD, so we have some space in front side of the server
to hole the 3rd PCI card. My question is if the PCI-X signals are still
pretty stable if we route them from the motherboard on the back side of the
server to the front side? I don't know what is the length limit of PCI-X
standard.

Another question is on PIC Express, the new PCI protocol. Since PCI Express
is a serial bus, so we may use a longer bus, right? Do you think we can
route its signals from the back side of the server to the front side for the
same reason?

Thanks,


T.
 
Hi,

I have a couple of questions on the PCI-X and PCI Express, and would
appreciate it if some one could help.

Most 1U servers let people install up to 2 PCI cards. For some reason, we
need to install 3 PCI cards in a 1U server, which normaly is very hard.
Click to expand...

The universe is expanding, soon you will find room for a 2U.
Since we just need 1 HDD, so we have some space in front side of the server
to hole the 3rd PCI card. My question is if the PCI-X signals are still
pretty stable if we route them from the motherboard on the back side of the
server to the front side? I don't know what is the length limit of PCI-X
standard.
Click to expand...

Google search it.
Another question is on PIC Express, the new PCI protocol. Since PCI Express
is a serial bus, so we may use a longer bus, right? Do you think we can
route its signals from the back side of the server to the front side for the
same reason?

Thanks,
Click to expand...


Having never tried or tested it I can only assume that, no, you can't do
that. The signals are precisely timed and that will be an inescapable
limit in addition to the noise. At most if you had a pre-constructed
extender you could get maybe a couple inches.
With a custom (very expensive) made solution you might have a bridge
inbetween so effectively neither bus is that long. I have no idea if such
a product exists.
 
In comp.sys.hp.hardware L said:
I have a couple of questions on the PCI-X and PCI Express, and would
appreciate it if some one could help.
Click to expand...
Most 1U servers let people install up to 2 PCI cards. For some
reason, we need to install 3 PCI cards in a 1U server, which normaly
is very hard. Since we just need 1 HDD, so we have some space in
front side of the server to hole the 3rd PCI card. My question is
if the PCI-X signals are still pretty stable if we route them from
the motherboard on the back side of the server to the front side? I
don't know what is the length limit of PCI-X standard.
Click to expand...

Are you trying to do this as a motherboard designer, or as an end-user?

Can you elaborate as to why you need three I/O cards in a 1U server?
Perhaps there is a way to break that assumption.

rick jones
 
3 PCI cards in a 1U server? How about a 2U server instead. Don't mess with bus
extenders or anything else. A server is supposed to be reliable. Why have a
kludged up server? ... Ben Myers
 
Rick Jones said:
Are you trying to do this as a motherboard designer, or as an end-user?

Can you elaborate as to why you need three I/O cards in a 1U server?
Perhaps there is a way to break that assumption.
Click to expand...

Since the external space is limited, 1U unit is preffered, not 2U.

3 different PCI cards are required because different interfaces, such as FC
ports, are required.

Are there any servers with a couple of built-in FC ports?

Thanks,


T.
 
3 PCI cards in a 1U server? How about a 2U server instead. Don't mess with bus
extenders or anything else. A server is supposed to be reliable. Why have a
kludged up server? ... Ben Myers
Click to expand...

Can't use 2U server since the space is limited.

I heard that servers with PCI Express might use both on-board slots and
cable connections. If this is right, then the future servers may provide
cable extender. Can any one confirm/correct this?

Thanks,


T.
 
Since the external space is limited, 1U unit is preffered, not 2U.
Click to expand...
3 different PCI cards are required because different interfaces,
such as FC ports, are required.
Click to expand...
Are there any servers with a couple of built-in FC ports?
Click to expand...

Not that I'm aware of, but there are I believe dual-port FC
cards. Soo, unless you need 6 FC ports, a pair of I/O slots should
suffice (modulo bandwidth requirements). Although I'm not sure if a 1U
system would have the CPU oomph to drive that many FC's to their
limits and if FC connectivity is required, FC switches might seem to
be indicated. (Although that increases the U count...)

rick jones
 
Rick Jones said:
Not that I'm aware of, but there are I believe dual-port FC
cards. Soo, unless you need 6 FC ports, a pair of I/O slots should
suffice (modulo bandwidth requirements). Although I'm not sure if a 1U
system would have the CPU oomph to drive that many FC's to their
limits and if FC connectivity is required, FC switches might seem to
be indicated. (Although that increases the U count...)
Click to expand...

Thanks for the info.

We need to install 1 FC card with 2 ports, and another 2 PCI cards. It
seems the CPU bandwidth is enough to drive all of them, and the PCI-X
bandwidth should be okay too if we use 2 isolated PCI-X buses, correct?

Thanks,


T.
 
In comp.sys.hp.hardware L said:
Thanks for the info.
Click to expand...

BTW, you never did (or I missed) answer the end-user vs board designer
question...
We need to install 1 FC card with 2 ports, and another 2 PCI cards. It
seems the CPU bandwidth is enough to drive all of them, and the PCI-X
bandwidth should be okay too if we use 2 isolated PCI-X buses, correct?
Click to expand...

I've no idea what your bandwidth requirements are :) Nor what
frequency of PCI-X bus you are contemplating... Nor what CPUs would be
in this 1U system...

What are the other two PCI cards to have on them?

rick jones
 
BTW, you never did (or I missed) answer the end-user vs board designer
question...


I've no idea what your bandwidth requirements are :) Nor what
frequency of PCI-X bus you are contemplating... Nor what CPUs would be
in this 1U system...

What are the other two PCI cards to have on them?
Click to expand...

We just use the board so we are an end-user, not board desiner.

The other 2 PCI cards are similar with the FC card and consume similar
bandwidth of the PCI bus. That is why I think 2 isolated PCI-X buses should
be enough to support them. I don't CPU bandwidth is a problem since we can
use 2-3 GHz one or we can even use dual CPUs.

Thanks,


T.
 
I think you are searching for an impossible solution. I have no idea now to
install 3 PCI cards in a 2-slot chassis. A PCI bus extender, if one can be
found, would need to be on the outside of the system chassis. I suggest that
you reconsider a 2U chassis, and determine how to fit it in the space.

.... Ben Myers
 
In comp.sys.hp.hardware L said:
The other 2 PCI cards are similar with the FC card and consume
similar bandwidth of the PCI bus. That is why I think 2 isolated
PCI-X buses should be enough to support them. I don't CPU bandwidth
is a problem since we can use 2-3 GHz one or we can even use dual
CPUs.
Click to expand...

Well, an FC these days is 2 Gbit/s, which should be well-within the
limits of a PCI-X 133 MHx bus, or even 100 MHz.

I take it these mystery cards aren't GbE, if they were, I believe
there are also GbE+FC combo cards on the market.

I imagine that if the things on those other two cards are reasonably
well defined, if you were truely in a jam, you could probably hire
some outfit to take those chips, and some FC chips and slap them
behind a bridge onto the same card(s).

rick jones
 
Well, an FC these days is 2 Gbit/s, which should be well-within the
limits of a PCI-X 133 MHx bus, or even 100 MHz.

I take it these mystery cards aren't GbE, if they were, I believe
there are also GbE+FC combo cards on the market.

I imagine that if the things on those other two cards are reasonably
well defined, if you were truely in a jam, you could probably hire
some outfit to take those chips, and some FC chips and slap them
behind a bridge onto the same card(s).
Click to expand...

Thanks for the info and suggestions, Rick.

It's very helpful.


T.
 
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