[9fans] DPT PM2041W observations

[G. David Butler gdb@dbSystems.com]

>Cool.  Patch?

For DPO?  Change wren.c to encode DPO in cmd[1].
cmd[1] = 0x10;  For command queueing?  It won't help the current
DPT driver since it only sends one command to the card at a
time, just like the 154x driver that came with the system.
If you want to try, set msg[1] to 0x20 and msg[2] to 0.
To use command queueing you need to be able to send multiple
commands to each *target*!

>> So why does this 4th generation card with tag queueing support
>> run slower than the 1st generation design that is over 10 years
>> old?
>
>Perhaps the driver for the 1540 is better optimized as it's been
>around longer, and it's had more work put into it.  There might

Remember, I have written both drivers from scratch and each
is optimized for the controller it is talking to.

>be something in the DPT documentation that one can do with the 
>card that one can't do with a 1540 ( bus on/off? ).  1540 is a

Yes I know.  For the comparison I turned the 154x back to 12us
on and 2us off, to match the DPT.  I usally run the 154x at
13us on 1us off.

David Butler
gdb@dbSystems.com