rallee2{at}comcast.net wrote:

>Hello All
>  Thanks to Robert and David for the clarification which I found
surprising.  It has been many years since I had an all scsi box and even
then it was built from used (affordable to me) parts which were old enough
to barely feel the scsi advantage compared to my much more modern ATA box. 
I ended up back around Warp3 days using a 150Meg SCSI drive as a dedicated
swap file in an otherwise IDE box and that was pretty darn nice but
obviously kept me ignorant of multiple scsi devices on one bus.  I'm not
sure now where I got the idea of individual drive autonomy on a scsi bus
but apparently that was unwarranted and incorrect.  It is possible that I
jumped to a conclusion based on OS/2 and scsi's ability to read and write
to multiple devices simoultaneously.  In any case sorry for the negative
comment on LSI's tech support quality since it was I that was wrong.  I now
wonder if this will still be true in serial scsi.  This is idle curiosity
since the division between performance to cost rat

io has only tipped more in favor of IDE of late but it would be interesting to know.
>Thanks
>Jimmy
>
>  
>
LVD and standard SCSI devices will NOT operate on the same SCSI buss. So 
what was said earlier was true. Mixing LVD and standard SCSI on the same 
buss is likely to result in a non-functioning system

It is true that the buss speed is limited to the slowest device on the 
chain, usually CD-ROMs and Tape drives. Think of an older HDD like the 
150MB above. It ran at 10MBs. Many of the CD-ROMS at the time were only 
5MBS devices, so the buss would only run at 5MBS of both devices were on 
the same buss.

Neither SCSI, NOR SATA, NOR IDE, Nothing available on the PC can issue 
multiple commands to multiple devices at the SAME time!!

SCSI devices have a UNIQUE feature in that they can accept a command, go 
offline to complete the command, then come back online to complete the 
request. This way the controller can issue rapid fire serial commands to 
multiple devices, then as each device responds, accept the data from them.

IDE on the other hand locks the buss until the transaction completes. 
That is why you want to have your CDs on one IDE channel while your HDD 
is on the other channel.

With SCSI, you COULD (if your S/W permitted such), stream data from one 
CD and simultaneously write that data to another CD. The READ CD would 
have to run a bit faster than the WRITER so that the write buffer would 
always remain in a near full state, else have a large write buffer than 
is common.

Nearly all CD-Writer S/W out there assumes that you either have only one 
device to read/write, or that you are on IDE. So they read the source 
FIRST, then write to the destination.

The fastest buss speeds for SCSI CDs these days is 40MBS. most SCSI HDDs 
sold today are either U160 or U320. You still can't mix these on the 
same buss

-- 
Robert Gammon   42310
Houston, TX

It is AMAZING to see what our bodies can do to heal 
themselves when we give them the nutrients that they crave.
Vibe! is wonderful.  Thanks to Eniva for making this
product available to us.

See www.enivaexpress.com for more details.  10% off on your
order when you use the following discount code   EE42310




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