32bit slots and riser cards

Bogdan Costescu bogdan.costescu at iwr.uni-heidelberg.de
Thu Aug 28 18:44:24 EDT 2003

On Thu, 28 Aug 2003, Greg Lindahl wrote:

> Doesn't that mean that the Myrinet card is 5 volts, and you only have
> 3.3 volt PCI slots ?

Bingo. This is exactly what most people that wrote to me off-list probably 
missed, although I did mention that it doesn't fit because of a different 
keying - I should have probably mentioned this explicitly. All the 32bit 
slots that I've seen on these mainboards allow inserting such cards, which 
makes me believe that they support both 5V and 3.3V cards; but the 64bit 
slots are 3.3V only.

I don't have much experience with rackmounted systems, which it's probably 
evident, so I didn't know what to expect from a riser. Thanks to Alvin 
Oga's mention of Adexelec site, I was able to find out that the risers 
exist in many different variations. For example, I was wondering if such a 
riser exist that would allow mounting of the card from the edge toward the 
middle of the mainboard, while most common way is the other way around - 
I still need to find out if the case allows fixing of the card the other 
way around, but this is an easier problem to solve.

One other thing that turned me off was that in a system composed of only
Intel components (SE7501WV2 mainboard and SR2300 case) the 64bit PCI slots
on the mainboard allow inserting of the Myrinet card (but didn't try to
see if it works), while the riser cards that came with the case do not,
allowing only 3.3V ones - so the riser imposes additional limitations...

Bogdan Costescu

IWR - Interdisziplinaeres Zentrum fuer Wissenschaftliches Rechnen
Universitaet Heidelberg, INF 368, D-69120 Heidelberg, GERMANY
Telephone: +49 6221 54 8869, Telefax: +49 6221 54 8868
E-mail: Bogdan.Costescu at IWR.Uni-Heidelberg.De

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