еще данные из pdf
хорошее описание SCSI на примере винтов Seagate
http://www.seagate.com/support/disc/man ... 95486a.pdf
9.6.3 SCSI interface cable requirements
The characteristics of cables used to connect parallel interface drives are discussed in the ANSI standards referenced
in this section.
9.6.3.1 Cable requirements
The characteristics of cables used to connect Ultra320 SCSI parallel interface devices are discussed in detail
in Section 6 of ANSI Standard T10/1365D Rev. 3. The cable characteristics that must be considered when
interconnecting the drives described in this manual in a Ultra320 SCSI parallel, daisy-chain interconnected
system are:
? characteristic impedance (see T10/1365D Sections 6.3.3 and 6.3.4)
? propagation delay (see T10/1365D Sections 6.3.6 and 6.3.7)
? stub length (see T10/1365D Section 6.9)
? device spacing (see T10/1365D Section 6.9)
To minimize discontinuances and signal reflections, cables of different impedances should not be used in the
same bus. Implementations may require trade-offs in shielding effectiveness, cable length, number of loads
and spacing, transfer rates, and cost to achieve satisfactory system operation. If shielded and unshielded
cables are mixed within the same SCSI bus, the effect of impedance mismatch must be carefully considered.
Proper impedance matching is especially important in order to maintain adequate margin at FAST-20, FAST-
40, FAST-80, and FAST-160 SCSI transfer rates.
Note. For LVD operation, twisted pair cables are recommended. For LVD Fast-40 operation, twisted pair
cables are strongly recommended. For Fast-80 and Fast-160 operation, twisted pair cables are
required.
также
9.6.2 SCSI interface physical description
Cheetah 10K.6 SCSI drives support the physical interface requirements of the Ultra320 SCSI Parallel Interface-
4 (SPI-4), and operate compatibly at the interface with devices that support earlier SCSI-2 and SCSI-3
standards. It should be noted that this is only true if the systems engineering has been correctly done, and if
earlier SCSI-2 and SCSI-3 devices respond in an acceptable manner (per applicable SCSI Standards) to reject
newer Ultra320 protocol extensions that they don?t support.
The drives documented in this manual support single-ended and low voltage differential physical interconnects
(hereafter referred to as SE and LVD, respectively) as described in the corresponding ANSI SPI document referenced
in the preceeding paragraph. These drives implement driver and receiver circuits that can operate
either SE or LVD. However, they cannot switch dynamically between SE and LVD operation.
The drives typically operate on a daisy-chain interface in which other SCSI devices are also operating. Devices
on the daisy chain must all operate in the same mode, either SE or LVD, but not a mixture of these. On the
interface daisy chain, all signals are common between all devices on the chain, or bus, as it is also called. This
daisy chain of SCSI devices must be terminated at both ends with the proper impedance in order to operate
correctly. Do not terminate intermediate SCSI devices. In some cases, the SCSI devices at each end have
onboard termination circuits that can be enabled by installation of a jumper plug (TE) on the device. These termination
circuits receive power from either a source internal to the device, or from a line in the interface cable
specifically powered for that purpose. LC and LW model drives do not have onboard termination circuits. Some
type of external termination circuits must be provided for these drives by the end user or designers of the
equipment into which the drives will be integrated. See the ANSI T10 Standard referenced above for the maximum
number of devices that can successfully operate at various interface transfer rates on SE and LVD daisy
chains.
LC model drives plug into PCBA or bulkhead connectors in the host. They may be connected in a daisy chain
by the host backplane wiring or PCBA circuit runs that have adequate DC current carrying capacity to support
the number of drives plugged into the PCBA or bulkhead connectors. A single 80-pin I/O connector cable cannot
support the DC current needs of several drives, so no daisy chain cables beyond the bulkhead connectors
should be used. A single drive connected via a cable to a host 80-pin I/O connector is not recommended.
далее приводится табличка со скоростями для различных интерфейсов из которой следует что в режиме SE возможны режыми только до Ultra Fast-20. В режиме LVD до Fast-160 соотв.
из другой таблицы следует что макс скорость в этом режиме как раз и будет 40 Мб/c для режима wide (16 бит) что реально будет 20Мб/c при 8 битах что очнь похоже на мою ситуацию....
Осталось выяснить что является причиной сего косяка.
Думаю осилим. Винты я пробовал запускать как все в месте так и по одному.
Уехал за переходником 68 на 80...
(((( Ой как разочарован, первый опыт и тут на тебе...
результаты тестов и чем меряли ?
