[geeks] weird slowness??

[Phil Stracchino]

Jon Gilbert wrote:
> So I have this computer. It's a PC with XP Embedded (photo kiosk).
> 
> If the IDE ATA HD is hooked up by itself, it runs fast, and no issues.
> 
> If the IDE ATA HD is chained with the DVD-R drive then it runs  
> sloowwwww as hell. The drive read speeds seem to plummet, but it all  
> works fine. Just slow!! (I tried different DVD drives, and different  
> IDE cables to no benefit. The HD is in Master, the DVD in slave; the  
> HD is on the end of the cable then, there is a long stretch of cable,  
> then the DVD drive, then a short stretch of cable, then the  
> motherboard. That's the only way it will fit due to the weird case.)
> 
> Any ideas how I can solve this? It's driving me NUTS! Thanks!

The short version:  Don't chain two PATA devices on the same channel.
PATA has been broken in this regard since its inception.  Any time you
have two devices on the same channel, (1) the channel drops back to the
speed of the slowest device on the bus, and (2) you lose up to 60% of
*that* due to bus contention because PATA devices don't play nicely
together on the same channel and never have since day 1.


-- 
  Phil Stracchino, CDK#2     DoD#299792458     ICBM: 43.5607, -71.355
  alaric at caerllewys.net   alaric at metrocast.net   phil at co.ordinate.org
         Renaissance Man, Unix ronin, Perl hacker, Free Stater
                 It's not the years, it's the mileage.