* Original question ************************************************************
>
>Subject: Q: Fast vs Wide SCSI, advantages and compatibility
>
>Hello, I have a DEC 3000/500 and I want to buy another HD for it.
>I am looking at a 4gig Seagate Barracuda drive, or maybe a Quantum 4G.
>
>Considering the variety of SCSI standards out there, does anyone know
>whether or not the DEC 3000/500 supports Wide SCSI II. For some reason
>I am under the impression that it uses more than 50 pins in which case
>it obviously won't since the DEC has the standard 50 pin cable.
>
>Basically my question is: Can I stick a Wide SCSI II drive on a
>standard SCSI II bus? How about Fast SCSI II, and Fast Wide SCSI II drive?
>
* SUMMARY **********************************************************************
the DEC 3000/500 has a vanilla SCSI II interface. One thing is for
certain, you CANNOT connect any Wide type device to the standard
SCSI II, since wide uses 68pins instead of 50. As for FAST SCSI II on
a SCSI II bus, I have gotten conflicting information. The first message below
clearly states that it is NOT possible, yet people say they have done it.
Can anyone shed some more light on this.....
********************************************************************************
********************************************************************************
*************************************************************** Response 1-7 ***
>From mstover_at_icarus.lis.pitt.edu Mon Jul 17 19:08:47 1995
This recently appeared on the hpux admin list, thought
it might be helpful....
mark (mstover_at_lis.pitt.edu
---------- Forwarded message ----------
Date: Wed, 12 Jul 1995 13:38:40 -0400
From:whaynes.office/G=William/S=Haynes/DD=whaynes.office_at_mhs-tva.attmail.com
To: hpux-admin_at_cv.ruu.nl
Subject: [HPADM] Summary - SCSI II vs FAST and Wide SCSI
This is a reposting since several had problems with the encoded table.
I've had to re-arrange. But the essential information is the same.
Thanks again to all who responded.
...Bill
COMPARISION OF FEATURES: SCSI II .vs. Differential SCSI .vs. Fast & Wide SCSI
Characteristic Single-Ended SCSI
Other Names and Aliases 'Standard SCSI',
'SCSI',
'SCSI II', 'SE-SCSI',
'SCSI-II'
Compatible with other SCSI bus types Not compatible with
Differential or Fast/Wide
SCSI
Bus Transfer Rate 5 Mbytes/s
Data Bus Width 8 bits
# Connector Pins 50 pins
Max. Cable Length (including internal cables) 6 meters
Maximum Number of Devices 7 peripherals
Peripheral Devices Disks, CD-ROM, DAT,
Rewritable Optical
Minitowers, Tapes,
Arrays
Characteristic Differential SCSI
Other Names and Aliases 'Fast', 'Fast/Narrow',
'Diff-SCSI'
Compatible with other SCSI bus types Not Compatible with
Single-Ended or Fast/Wide
SCSI.
Bus Transfer Rate 10 Mbytes/s
Data Bus Width 8 bits
# Connector Pins 50 pins
Max. Cable Length (including internal cables) 25 meters
Maximum Number of Devices 7 peripherals
Peripheral Devices Disks, Arrays(1350SX)(1350SA)
Characteristic Fast/Wide SCSI
Other Names and Aliases 'Differential-Wide',
'F/W-SCSI', 'Fast and Wide'
Compatible with other SCSI bus types Not Compatible with
Single-Ended or Differential
SCSI.
Bus Transfer Rate 20 Mbytes/s
Data Bus Width 16 bits
# Connector Pins 68 pins
Max. Cable Length (including internal cables) 25 meters
Maximum Number of Devices 15 peripherals
Peripheral Devices Minitowers, Arrays
(C303x Products) HP 9000
Models 735 and 755 only.
*************************************************************** Response 2-7 ***
>From alan_at_nabeth.cxo.dec.com Mon Jul 17 19:23:54 1995
It is most accurate to say that there is one SCSI-2 spec
with lots of options. Wait till you see SCSI-3...
The built-in SCSI adapter of the DEC 3000 Model 500 (and
400) is a single-ended, narrow, 5 Mhz SCSI. It won't
do fast and won't do wide. If you can connect a wide
drive to a narrow bus, the best that will happen is
that the drive will realized that it has nothing useful
connected to the extra wires used by wide and will use
narrow transfers. At worst half the data will get lost
since it doesn't have a path back to the host. I don't
know what SCSI-2 is supposed to do in this case.
The PMAZC (add-on TURBOchannel adapter) supports Fast
SCSI, if you can keep the cables short enough; 3 meters.
It is a dual channel adapter and basically the fast version
of the Model 500 built-in adapter. The KZTSA adapter
supports Fast and Wide devices. It also uses differential
cabling, so you may need a converter between drives and
the adapter.
Unfortunately, Digital UNIX doesn't currently support
wide addressing. Apparently one of the other benefits of
Wide SCSI, in addition to 16 bit transfers, is another
device address bit. This allows 15 devices instead of the
7 allowed by narrow SCSI. Digital UNIX does support wide
transfers, but not wide addresses. This will be fixed in
a future release.
*************************************************************** Response 3-7 ***
>From gadbois_at_mcc.com Mon Jul 17 20:01:13 1995
The 50 wire cabling is used for non-wide SCSI. There are at least two
kinds of external 50-pin connectors in use in the SCSI world: The large
Centronics-style connector with the wire clip things and the
"mini-micro" plug. My 3000/500 has the Centronics-style connector, but
it may be a strange one (it was an early demo box.) Most of the Fast
SCSI II external drive cases use the mini-micro connectors, so I have to
use a converter cable to hook to my first external device.
Basically my question is: Can I stick a Wide SCSI II drive on a
standard SCSI II bus?
No, the wide cabling is different -- more pins. And the host interface
has to support Wide SCSI II, which the controllers I have don't.
How about Fast SCSI II,
Yes, this will work. I have hooked up a Seagate Elite 9 to my 3000/500.
and Fast Wide SCSI II drive?
No, not enough pins.
*************************************************************** Response 4-7 ***
>From bgk1142_at_bggfu2.nho.hydro.com Tue Jul 18 02:57:08 1995
Hi !
As far as I know there are only scsi II, fast scsi II and fast&wide scsi
II. I've never heard of wide scsi II only.
As for your questions:
1. No , you cannot put a fast&wide disk on a regular scsi II controller.
2. Yes, you can put a fast scsi II disk on a regular scsi II controller
3. Yes, you can put a scsi II disk on a fast scsi II controller.
In both cases 2&3 the performance will be of scsi II, NOT fast scsi II,
because the performance will be equal to the lowest performance in the
chain.
*************************************************************** Response 5-7 ***
>From olle_at_cb.uu.se Tue Jul 18 03:46:34 1995
3000/500 models do not support wide SCSI as standard. There are optional
turbochannel cards that support wide SCSI however. Fast SCSI II it not
supported either at least not in early 500 models, also optional.
*************************************************************** Response 6-7 ***
>From morten.hanshaugen_at_usit.uio.no Tue Jul 18 04:31:10 1995
> Basically my question is: Can I stick a Wide SCSI II drive on a
> standard SCSI II bus? How about Fast SCSI II, and Fast Wide SCSI II drive?
SCSI, SCSI II, FSCSI II on the one hand and Wide SCSI are two totally
different standards. So there is no way you can use a Wide SCSI disk
on a Narrow SCSI-controller, and what good would it come from it? The
slowest disk sets the pace ...
Morten
*************************************************************** Response 7-7 ***
>From NMH1_at_axprl1.rl.ac.uk Tue Jul 18 05:18:13 1995
DEC 3000/500 has two Fast SCSI II channels, one internal, one external. You
can set either slow or fast mode on these busses via the console. If you want
to use wide devices then you need another SCSI card. The KZTSA gives you a
Fast Wide Differential SCSI via a Turbochannel slot. You are correct about
the pins, FWD uses a 68pin connect. You cannot as far as I know stick a wide
drive on a non wide SCSI bus.
********************************************************************************
Responses From:
mstover_at_icarus.lis.pitt.edu
alan_at_nabeth.cxo.dec.com
gadbois_at_mcc.com
bgk1142_at_bggfu2.nho.hydro.com
olle_at_cb.uu.se
morten.hanshaugen_at_usit.uio.no
NMH1_at_axprl1.rl.ac.uk
--
All things are connected.
Received on Tue Jul 18 1995 - 15:03:35 NZST