Confused about my Adaptec LVD/SE card's bus independence
Jeff T.
LVD and SE device.
There is an Ultra2-LVD onboard connector (special LVD cable to LVD
HDD) and a SE-68 pin onboard connector (to a Plextor UltraPlexWIDE -
SE SCSI CDROM).
Configured this way, the performance I measured from the CDROM was
only 6x but when I removed the LVD HDD and dedicated the CDROM to
*just* the SE connection, performance jumped to over 32x.
My understanding was that with this card, I in effect, had two
separate buses (LVD and SE) and that there wouldn't be a performance
hit for either SCSI device. Note: these devices are not on the same
SCSI cable. Th LVD device has it's own LVD cable and the CDROM has
it's own SE cable.
Am I mistaken? Am I also robbing performance of my LVD hard drive by
using the SE device on the same card as the LVD device?
Please help clarify the bandwidth implications of using this card with
multiple devices on separte ports (i.e. not on same SCSI chain).
thank you,
Jeff
Arno Wagner
> I'm confused about co-habitating this SCSI card (2940U2W) with both a
> LVD and SE device.
> My understanding was that with this card, I in effect, had two
> separate buses (LVD and SE) and that there wouldn't be a performance
> hit for either SCSI device. Note: these devices are not on the same
> SCSI cable. Th LVD device has it's own LVD cable and the CDROM has
> it's own SE cable.
>
> Am I mistaken? Am I also robbing performance of my LVD hard drive by
> using the SE device on the same card as the LVD device?
out there: Those with one channel, meaning the SE connector is just
that: An SE connector to the LDV bus, slowing the LDV when something
is connected to it. Saves an expensive adapter. Those with two
channels, sometimes both LDV sometimes one LDV and one SE. No
cross-slowing here. These cards are much more expensive. I think
I remember even one card with two LDV channels and an SE bridge.
The bus with the SE bridge (that is not just a physical connection
but a SCSI-to-SCSI converter with processor, storage, etc.) on
it would not be slowed down when something is connected to the
SE bus.
So yes, unlsee you have a dual channel controler or one with an
SE-to-LDV SCSI bridge connectiong anything to the SE connector
witt turn the wohle bus into SE, as the SE devices cannot deal
with the LDV electrical signals.
Arno
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Folkert Rienstra
"Arno Wagner" <sp...@komsys-pc-aw.ethz.ch> wrote in message news:abtl2l$ks8od$1...@ID-2964.news.dfncis.de...
: In comp.sys.ibm.pc.hardware.storage Jeff T. <sax...@mindspring.com> wrote:
: > I'm confused about co-habitating this SCSI card (2940U2W) with both a
: > LVD and SE device.
: [...]
: > My understanding was that with this card, I in effect, had two
: > separate buses (LVD and SE) and that there wouldn't be a performance
: > hit for either SCSI device. Note: these devices are not on the same
: > SCSI cable. Th LVD device has it's own LVD cable and the CDROM has
: > it's own SE cable.
: >
: > Am I mistaken? Am I also robbing performance of my LVD hard drive
: > by using the SE device on the same card as the LVD device?
:
: I don't know about your card, but there are different types of LDV cards
: out there: Those with one channel, meaning the SE connector is just that:
That is contradictive to what you say at the bottom
: An SE connector to the LDV bus,
It can't be one if it is connected to the LVD segment, in which
case it is just another connector. There are no LVD and SE con-
nectors at an LVD bus without LVD-SE bridges. You can't say
that a narrow connector automatically must be a SE connector.
: slowing the LDV when something is connected to it.
If a connector is labeled SE then it is connected to a SE segment.
: Saves an expensive adapter. Those with two
: channels, sometimes both LDV sometimes one LDV and one SE. No
: cross-slowing here. These cards are much more expensive. I think
: I remember even one card with two LDV channels and an SE bridge.
: The bus with the SE bridge (that is not just a physical connection
: but a SCSI-to-SCSI converter with processor, storage, etc.) on
You made that up, didn't you?
: it would not be slowed down when something is connected to the SE bus.
:
:
Folkert Rienstra
"Jeff T." <sax...@mindspring.com> wrote in message news:sfp3eu80c9s1de67m...@4ax.com...
: I'm confused about co-habitating this SCSI card (2940U2W) with both
:
: There is an Ultra2-LVD onboard connector (special LVD cable to LVD
: HDD) and a SE-68 pin onboard connector (to a Plextor UltraPlexWIDE -
: SE SCSI CDROM).
:
: Configured this way, the performance I measured from the CDROM was
: only 6x but when I removed the LVD HDD and dedicated the CDROM to
: *just* the SE connection, performance jumped to over 32x.
Are you using XP?
:
: My understanding was that with this card, I in effect, had two
: separate buses (LVD and SE)
Segments actually.
: and that there wouldn't be a performance
: hit for either SCSI device. Note: these devices are not on the same
: SCSI cable. The LVD device has it's own LVD cable and the CDROM has
: it's own SE cable.
:
: Am I mistaken?
No, not really.
: Am I also robbing performance of my LVD hard drive by
: using the SE device on the same card as the LVD device?
No. Not in the sense of the bus shifting to SE all the way.
And even if it did, that would not lead to what you are seeing.
:
: Please help clarify the bandwidth implications of using this card with
: multiple devices on separte ports (i.e. not on same SCSI chain).
chain = channel = bus. They are all on the same bus so any transfers that
are executed at lower rates than the maximum possible, eat away from the
max. usable bandwidth that the host may provide when all devices transfer
at the maximum bus rate.
:
: thank you,
: Jeff
:
Mr Garfield
isolates the SE connection(s) from the LVD bus when the SE
device is not selected. However, when selected, the SE
device still takes the entire SCSI bus down to SE speed.
There are several different connectorizations of a 2940U2W,
Q: What connectors does yours have ?
Mine has an external HD50 (SE), and internal 50 (SE), and a internal
68 (LVD)
If the card does not have a LVD to SE converter in it then
the controller must use SE to talk to all the devices so that all
the devices (including the SE device) can decode the bus cycles.
A dual channel controller like a 3960D is another story -:)
Now for your case: you say that when you take off the LVD device
your SE device goes much faster...
Couple of questions:
1) What are you doing when you measure the CD speed ?
2) The follow up question you have to ask is: "Are any of the other
devices on the SCSI channel being accessed ?" ... like for a swap
file, temp file etc
3) What are your CTRL-A settings ?
Post that and I will compare those settings against mine.
Garfield
On Wed, 15 May 2002 04:37:26 GMT, Jeff T. <sax...@mindspring.com>
wrote:
Folkert Rienstra
"Mr Garfield" <garfi...@hotmail.com> wrote in message news:uoa6euomh0hmttqm6...@4ax.com...
: Your 2940U2W should have a (mine does) SE to LVD converter on it that
: isolates the SE connection(s) from the LVD bus when the SE
: device is not selected. However, when selected, the SE
: device still takes the entire SCSI bus down to SE speed.
Ofcourse, as will every other device, LVD or SE, that has
negotiated a speed that is lower than the maximum one.
:
: There are several different connectorizations of a 2940U2W,
: Q: What connectors does yours have ?
The same as your 2940U2W ofcourse, that is, if you have one.
: Mine has an external HD50 (SE), and internal 50 (SE), and a internal
: 68 (LVD)
Then obviously you don't have a 2940U2W.
Sounds like a 2930U2 or a 19160/29160N to me.
The 2940U2, like the 2940U2W, also has 4 connectors. The 2940U2B
only has wide internal and external connectors as it doesn't have the
SpeedFlex chip.
:
: If the card does not have a LVD to SE converter in it then
: the controller must use SE to talk to all the devices so that all
: the devices (including the SE device) can decode the bus cycles.
:
: A dual channel controller like a 3960D is another story -:)
Yeah, like U160 vs U80.
:
: Now for your case: you say that when you take off the LVD device
: