BCM Advanced Research
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The IN440EX motherboard support ISA and PCI expansion buses to implement up to
two (2) ISA and two (2) PCI slots. The IN440EX will support one (1) ISA, one (1)
PCI and one (1) shared ISA/PCI NLX slot.
ISA Bus Speed
Dividing the PCI clock by 4 generates the ISA system clock. The divide by 4 setting is
used for 30MHz and 33MHz PCI bus speed. The frequencies supported are 7.5MHz
and 8.33MHz.
AT Bus Refresh
The IN440EX system board supports
hidden
refresh cycles which allows the CPU to
continue to execute unless an AT bus cycle is attempted coincident with the AT bus
refresh cycle (ISA Bus refresh cycles are completely decoupled from DRAM Refresh).
Transactions driven by PCI masters that target ISA or IDE resources while refresh is
active are held off with wait states until the refresh is complete.
Storage Subsystem
IDE Hard Disk Drive Interface
The IN440EX provides two (2) independent high performance bus-mastering PCI IDE
interfaces capable of supporting PIO Mode 3, Mode 4 and ‘Ultra33’ Synchronous
DMA mode devices. The integrated IDE interface can control up to four IDE devices
allowing for both CD-ROM and Hard Disk drives. IDE PRI & IDE SEC are the
primary and secondary IDE connectors respectively. Both IDE controllers can be
disabled through BIOS to allow for external disk drive controllers.
Floppy Disk Drive Interface
The IN440EX has an integrated 765B compatible floppy disk controller using the
Winbond’s W83977TF component. The FDC sub-section can control one (720KB, 1.2,
1.44 or 2.88MB) floppy disks or compatible tape drives. The floppy I/O address can be
relocated to 480 different locations. 13 IRQ and 3 DMA channel options are available
as well. Includes multiple power down modes for reduced power use.
The floppy disk interface contains 48mA drivers and Schmitt trigger inputs on the drive
interface.
