HP Vectra XU 6/XXX HP Vectra XU 6/xxx and VT 6/xxx PCs - Technical Reference M - Page 20

Other Pci Accessory Devices

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Transfer Rates Versus Modes of Operation The controller supports 32-bit Windows and DOS I/O transfers (many IDE controllers use Windows integral IDE driver which only supports 16-bit I/O transfers). It has PCI master capability, and supports programmed I/O (PIO) modes up to mode 4 and direct memory access (DMA) modes up to mode 2 (giving a cycle time of 120 ns, and a transfer rate of 16.7 MB per second, in both cases). The five PIO modes allow the following transfer rates: Mode 0 1 2 3 4 Cycle time (ns) 600 383 240 180 120 Transfer rate (MBytes/s) 3.33 5.22 8.33 11.1 16.7 The three DMA modes allow the following transfer rates: Mode 0 Cycle time (ns) 480 Transfer rate (MBytes/s) 4.2 1 2 150 120 13.3 16.7 Operated in SLAVE mode, the IDE controller saturates the PCI bus with transfers, thus limiting the actual achieved transfer rate to 4 or 5 MBytes per second. Operated in MASTER mode, though, the IDE controller is allowed to work autonomously of the CPU, and the full 16.7 MBytes per second transfer rate can be achieved, with less than 33% occupancy of the PCI bus (so allowing the CPU to get on with other work for more than 67% of the cycle times, whilst the IDE transfers are going on in parallel). Disk Capacity Versus Modes of Addressing The amount of addressable space on a hard disk drive is limited by three factors: the physical size of the hard disk, the addressing limit of the IDE hardware, and the addressing limit of the BIOS. The Extended-CHS addressing scheme allows larger disk capacities to be addressed than under CHS, by performing a translation (for example regrouping the sectors so that there are twice as many logical tracks as is possible under the CHS addressing scheme). If the Setup field has been set to automatic, the logical block addressing (LBA) mode will be selected for each device that supports it. CHS ECHS LBA Cylinders per Device 64 64 - Heads per Cylinder 16 256 - Sectors per Track 1024 1024 256 M (=228) Bytes per Sector 512 512 512 Bytes per Device 528 M 8.4 G 137 G OTHER PCI ACCESSORY DEVICES PCI accessory boards are for high-speed peripheral accessories. There are four slots on the PCI bus for accessory boards. One of these is already occupied by the video controller board, and a second (on the HP Vectra XU 6/ xxx PC) by the LAN board; these are described in the next chapter. The fourth slot is a combination slot with the ISA bus.

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Transfer Rates Versus Modes of Operation
The controller supports 32-bit Windows and DOS I/O transfers (many IDE controllers use Windows
integral IDE driver which only supports 16-bit I/O transfers). It has PCI master capability, and
supports programmed I/O (PIO) modes up to mode 4 and direct memory access (DMA) modes up
to mode 2 (giving a cycle time of 120 ns, and a transfer rate of 16.7 MB per second, in both
cases). The five PIO modes allow the following transfer rates:
Mode
0
1
2
3
4
Cycle time (ns)
600
383
240
180
120
Transfer rate (MBytes/s)
3.33
5.22
8.33
11.1
16.7
The three DMA modes allow the following transfer rates:
Mode
0
1
2
Cycle time (ns)
480
150
120
Transfer rate (MBytes/s)
4.2
13.3
16.7
Operated in SLAVE mode, the IDE controller saturates the PCI bus with transfers, thus limiting the
actual achieved transfer rate to 4 or 5 MBytes per second. Operated in MASTER mode, though,
the IDE controller is allowed to work autonomously of the CPU, and the full 16.7 MBytes per
second transfer rate can be achieved, with less than 33% occupancy of the PCI bus (so allowing
the CPU to get on with other work for more than 67% of the cycle times, whilst the IDE transfers
are going on in parallel).
Disk Capacity Versus Modes of Addressing
The amount of addressable space on a hard disk drive is limited by three factors: the physical size
of the hard disk, the addressing limit of the IDE hardware, and the addressing limit of the BIOS.
The Extended-CHS addressing scheme allows larger disk capacities to be addressed than under
CHS, by performing a translation (for example regrouping the sectors so that there are twice as
many logical tracks as is possible under the CHS addressing scheme). If the
Setup
field has been
set to
automatic
, the logical block addressing (LBA) mode will be selected for each device that
supports it.
Cylinders
per Device
Heads per
Cylinder
Sectors
per Track
Bytes per
Sector
Bytes per
Device
CHS
64
16
1024
512
528 M
ECHS
64
256
1024
512
8.4 G
LBA
-
-
256 M
(=228)
512
137 G
OTHER PCI ACCESSORY DEVICES
PCI accessory boards are for high-speed peripheral accessories. There are four slots on the PCI
bus for accessory boards. One of these is already occupied by the video controller board, and a
second (on the
HP Vectra XU 6/ xxx PC
) by the LAN board; these are described in the next
chapter. The fourth slot is a combination slot with the ISA bus.