Fast SCSI 2
By Hart - usenet poster
I need to add another HD to a Compaq ProSignia 500 (P90) with integrated
Fast SCSI-2 controller. Called Northamber and they asked whether the
cable was 50 or 68 pin.
I am not often found with my head stuck inside a server nowadays, but I
thought that Fast SCSI-2 was always 50 pin.
Help, please.
Ernest
--
ernest at Noel Systems, Folkestone (UK)
(if replying by email, use postmaster)
Solution #1
posted on Aug 02, 2007
Joey2 - usenet poster
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Yes. One of the fortunate things about SCSI, is the way the devices
work. All the initial communications (even on the latest fastest
drives), is done at the old SCSI-1 rates. The controller then asks
each device what extensions it supports. It will then switch up to the
highest common 'extension' supported both by itself and the device. So
a 'ultra' drive, will run happily on a Fast SCSI-2 interface, just
running at the 10Mhz rate. This is why drive manufacturers felt safe
dropping the older interface, since the newer standards are all
reverse compatible :-)
Best Wishes
work. All the initial communications (even on the latest fastest
drives), is done at the old SCSI-1 rates. The controller then asks
each device what extensions it supports. It will then switch up to the
highest common 'extension' supported both by itself and the device. So
a 'ultra' drive, will run happily on a Fast SCSI-2 interface, just
running at the 10Mhz rate. This is why drive manufacturers felt safe
dropping the older interface, since the newer standards are all
reverse compatible :-)
Best Wishes
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Solution #2
posted on Aug 02, 2007
Jimmy NY - usenet poster
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The string 'Fast SCSI-2' is the exact terminology used in the Compaq
manual for this server. The controller is integrated on the motherboard.
I can get the details from the existing hd as supplied with the server
but I'm now sure it's 50 pin.
Will any standard (eg seagate, etc) modern scsi hd with 50 pin work in
conjunction with existing old hd?
But I'm not looking for a cable. :)
Ernest
--
ernest at Noel Systems, Folkestone (UK)
(if replying by email, use postmaster)
manual for this server. The controller is integrated on the motherboard.
I can get the details from the existing hd as supplied with the server
but I'm now sure it's 50 pin.
Will any standard (eg seagate, etc) modern scsi hd with 50 pin work in
conjunction with existing old hd?
But I'm not looking for a cable. :)
Ernest
--
ernest at Noel Systems, Folkestone (UK)
(if replying by email, use postmaster)
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Solution #3
posted on Aug 02, 2007
Kim1 - usenet poster
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[SNIP erudite discussion]
My take on these various versions is that most speakers don't
understand them in detail, so when someone talks to me about such
things I am usualy wondering 'What do they mean by SCSI 2?'
I usualy find it easier to say 'a cable for a Seagate ST<whatever to an Adaptec 2940U'!
Regards,
Harry.
My take on these various versions is that most speakers don't
understand them in detail, so when someone talks to me about such
things I am usualy wondering 'What do they mean by SCSI 2?'
I usualy find it easier to say 'a cable for a Seagate ST<whatever to an Adaptec 2940U'!
Regards,
Harry.
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Solution #4
posted on Aug 02, 2007
Jimmy NY - usenet poster
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Not inherently. This is where the 'fast' bit comes in. SCSI-2, added
some extra protocols to SCSI, and it is possible to have a 'SCSI-2'
device that is only 5MB/sec. 'Fast SCSI-2' implies the use of the
10MB/sec rates. However the industry really went straight to the
faster rates, so 99% of 'SCSI-2' devices are automatically 'Fast
SCSI-2', and support the use of sync signalling at the 10MHz rate.
There is a problem here, in that the 'wide' format of SCSI-2, used two
seperate cables, and was never really implemented. The 'wide' variant
that all the manufacturers used, was never part of the SCSI-2
'standard', but only exists in the SCSI-3 proposals. Fun Huh...
This is where the problems with SCSI exist. With each 'switch' to a
faster protocol, manufacturers will bring out their own 'versions'
ahead of the actual protocol being standardised. The same has
happended with the next changes 'ultra' etc., and so drives were
launched with these faster data rates, long before the standards were
ratified - at present most devices are actually SCSI-2, with the
faster signalling rates from the SCSI-3 proposals, or the (now
ratified) use of the 68pin 'wide' connector. (these faster rates have
now been ratified as a standard).
And of course now Ultra160 - 68 pins, LVD signalling, 160MB/sec.
No. Fast SCSI-2, is the full term for the use of the 10MB/sec
signalling standard of SCSI-2. 'Ultra', was originally proposed as
being called 'Fast20', but the manufacturers used ultra, and this
eventually became adopted. The full SCSI-3 proposals have still not
all been ratified.
You are closer than many who claim to understand SCSI!. The problem is
that you are dealing with a moving target, and also a lot of 'grey
areas' when the new proposals go for ratification, before becoming and
ANSI standard.
It is very fun.
Best Wishes
some extra protocols to SCSI, and it is possible to have a 'SCSI-2'
device that is only 5MB/sec. 'Fast SCSI-2' implies the use of the
10MB/sec rates. However the industry really went straight to the
faster rates, so 99% of 'SCSI-2' devices are automatically 'Fast
SCSI-2', and support the use of sync signalling at the 10MHz rate.
There is a problem here, in that the 'wide' format of SCSI-2, used two
seperate cables, and was never really implemented. The 'wide' variant
that all the manufacturers used, was never part of the SCSI-2
'standard', but only exists in the SCSI-3 proposals. Fun Huh...
This is where the problems with SCSI exist. With each 'switch' to a
faster protocol, manufacturers will bring out their own 'versions'
ahead of the actual protocol being standardised. The same has
happended with the next changes 'ultra' etc., and so drives were
launched with these faster data rates, long before the standards were
ratified - at present most devices are actually SCSI-2, with the
faster signalling rates from the SCSI-3 proposals, or the (now
ratified) use of the 68pin 'wide' connector. (these faster rates have
now been ratified as a standard).
And of course now Ultra160 - 68 pins, LVD signalling, 160MB/sec.
No. Fast SCSI-2, is the full term for the use of the 10MB/sec
signalling standard of SCSI-2. 'Ultra', was originally proposed as
being called 'Fast20', but the manufacturers used ultra, and this
eventually became adopted. The full SCSI-3 proposals have still not
all been ratified.
You are closer than many who claim to understand SCSI!. The problem is
that you are dealing with a moving target, and also a lot of 'grey
areas' when the new proposals go for ratification, before becoming and
ANSI standard.
It is very fun.
Best Wishes
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