On 14 Jul 1999, Marc SCHAEFER wrote:
[ ... ]
> - the 390U2W is a plain standard SYM53c896, thus supported by the standard
> ncr53c8xx Linux driver, as all SYM53c896 implementations. There is also
> a version with electrical isolators so to be able to run U2LVD and U SE
> simultaneously. I have that version working with IBM DDRS U2LVD drives
> and SE tape drive. (Ultra II LVD, 80 Mbyte/s). Open Source Linux driver.
Not may guess from the description on this board by Tekram.
My understanding is that both the 390U2B and 390U2W are based on the
SYM53C895 chip.
The 390U2W uses a SCSI-to-SCSI converter (SYM53C141 or something like
that) that allows to use both LVD and SE devices at the same time, but:
- It only _is_ 1 SCSI BUS in term of SCSI resource.
- It is about the same price as a (390F + 390U2B) pair that allows same
configurations but offers actually 2 separate SCSI BUSes.
My opinion:
-----------
Since LVD signaling is very sensitive to release glitches I donnot want
old SCSI devices to interfere on a SCSI BUS with LVD devices with control
signals, even in a situation of some magic chip doing kind of isolation
and signal/timing rewamping between the LVD and SE BUS branch.
The '2 controllers' solution or the real 53C896 solution looks to me a
more safe approach for the support of both LVD and SE on a system, and
allows for sure better performances.
[ ... ]
G�rard.
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