Twinax/ethernet cards and freezing conflicts; was x

[Jerome Draper <jdraper@xxxxxxx>]

At 09:30 AM 8/25/98 -0700, you wrote:
>At 07:01 PM 8/24/98 -0600, you wrote:
>>No, it's not guaranteed to cause locks/hangs, but it HAS occured at 3 of
>>our customers in the last 6 months !

This could be of interest to those facing PC conflicts and mysterious
freezeups:

As we all know, there are now PC's beyond the ole 8bit ISA style that have
16bit and 32bit (PCI) busses.  

8bit ISA cards are limited to 8bit data paths and yet decode 10bit i/o
addresses.  16bit cards decode 16 address bits and 32bit cards decode 32
address bits.  All addresses are visible on the buss of the PC to all cards
no matter whether they are 8bit, 16bit, or 32bit.  Each card decodes what
it needs or is allowed to decode.

There is an address overlay possibility of that can happen because some
cards can only decode part of the total address.

For example, an address of 0B03 decoded by a 32bit PCI card would conflict
with address 0303 decoded by an 8bit ISA card.  If you decode the first 10
bits of either address you come up with 303 (the 12th address bit is not
checked by the 8bit cards).

B03 as binary would be 0000 1011 0000 0011
303 as binary would be        11 0000 0011

If an 8bit card sees the 303 it reponds to that address no matter whether
it's B03 or 303.  

Conslusion:

There are cases where changing the I/O address may solve the freezing
problem even when there is no aparent conflict.

Regards,


Jerry



Jerry Draper, Trilobyte Software Systems, since 1976
Specializing in connecting PC's, Windows, MAC's, and LAN's to the AS/400
Representing Synapse, Apple, IBM, UDS, Nlynx, MI, DCI, Netsoft, etc.
(415) 457-3431; (415) 258-1658fax; jdraper@wco.com
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