[SunRescue] Re: LVD drive on SCSI-2
james at foonly.com
Wed May 24 11:47:05 CDT 2000
On Wed, 24 May 2000, Chris Powell wrote:
> The LVD standard is far funkier than just being differential. Proper
> LVD drives should sense if the bus is SE or differential, 8-bit or
> 16-bit and work accordingly. Really rather impressive!
In most cases LVD can fall back to SE mode. It cannot fall back to HVD
(high voltage differential or just "differential"). The reason for
developing LVD in the first place was that HVD line drivers couldn't be
efficiently packaged into a controller ASIC and this made HVD cards more
expensive. LVD uses TTL signalling levels, this gives it less range than
HVD but makes it cheaper.
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