Hi,

I have heard that on some PCI slot on some motherboard, there isn't
#GNT and #REG connected , that mean the slot don't support master
PCI on it , is this true?
And how can i know which slot on the motherboard are 33MHZ slot and
which are 66 MHZ slot ? after i have plugged my PCI card and start the
machine, how can i know which frequency it is running at ?


Regards,
TOM

Hi Tom, it's correct, some older boards do have some PCI slots which are not busmaster capable. It's because older chipsets do not provide enough #REQ/#GNT pairs for all slots. As far as i know, this problem occours only on boards from the beginning of PCI (about 1995). Newer chipsets should have all slots busmaster capable. To check this, you can for example take a look into the chipset specification or ask your vendor. A 66 MHz slot can't be detected only by watching. To be sure it's better to take a look into your manual. An circumstantial evidence is the voltage of the slot. 66MHz slots only run on 3.3V, not on 5V. A 3.3V slot differs from a 5V slot in the direction of the slot itself. It is turned by 180 degrees. front __________________________________________ | | | 5V slot -------------------------------------------------------- __________________________________________ | | | 3.3V slot -------------------------------------------------------- Take a look at http://hsi.web.cern.ch/HSI/s-link/devices/s32pci64/slottypes.html You can detect it by one signal (name: 66enable or something like this) which was redefined from ground (on 33MHz platforms) to pulled up (on 66MHz platforms). If a 33 MHz card is plugged into a 66MHz segment, this card pulls this line to ground, the bridge detects a 33MHz device and switches the whole bussegment to 33 MHz. A 66 MHz card leaves this signal floating. If you want to know if your bussegment is running on 66MHz, find out if your bridge supports this, find the signal and take a measurement. If the level is high when the cards are inserted, the segment is running on 66MHz, if it is low, it's not. But keep in mind: This signal is bussed, this means one 33 MHz device plugged in will slow down the whole bussegment. I don't know if there is a softwaresolution to get this information. Maybe there is something in the datasheet of your bridge. Bye, Adalbert tomko81@hotmail.com wrote: