HP Vectra 500 Series - Manual (Page 51)

51
2 System Board - (SiS Chipset) (Part Number: D4051-63001)
Devices on the PCI Bus
The three DMA modes allow the following transfer rates:
Operated in slave mode, the IDE controller saturates the PCI bus with
transfers, thus limiting the actual achieved transfer rate to less than
10 MBytes per second.
Operated in master mode, though, the IDE controller is allowed to work
autonomously of the processor, and the full 16.7 MBytes per second transfer
rate can be achieved with less than 33% occupancy of the PCI bus (thus
allowing the processor to do other work for more than 67% of the cycle
times, while the IDE transfers take place in parallel).
Disk Capacity Versus Modes of Addressing
The amount of addressable space on the hard disk is limited by three
factors:
• Physical size of the hard disk.
• Addressing limit of the IDE hardware.
• Addressing limit of the BIOS.
The Extended-CHS (Cylinder Header Sector) 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.
Mode 0 1 2
Cycle time (ns) 480 150 120
Transfer rate (MBytes/s) 4.2 13.3 16.7
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 (=2
28
) 512 137 G