TYAN Transport TN27 B4987, Service Manual

Page: 111 / 135

Feature Option Description
NorthBridge Chipset Configuration
CAS Latency (Tcl) Read only
This controls the timing delay (in clock
cycles) before SDRAM starts a read
command after receiving it.
RAS/CAS Delay (Trcd) Read only
When DRAM is refreshed, both rows
and columns are addressed
separately. This setup item allows you
to determine the timing of the transition
from RAS (row address strobe) to CAS
(column address strobe). The less the
clock cycles, the faster the DRAM
performance.
Min Active RAS (Tras) Read only
This setting allows you to select the
number of clock cycles allotted for the
RAS pulse width, according to DRAM
specifications. The less the clock
cycles, the faster the DRAM
performance.
Row Precharge Time
(Trp) Read only
This item controls the number of cycles
for Row Address Strobe (RAS) to be
allowed to precharge. If insufficient
time is allowed for the RAS to
accumulate its chage before DRAM
refresh, refresh may be incomplete and
DRAM may fail to retain data. This
item applies only when synchronous
DRAM is installed in the system.
RAS/RAS Delay (Trrd)
Read only
Auto uses hardware compensation
values. Other values add to or subtract
from hardware generated value.
Recommended setting is Auto.
Row Cycle (Trc) Read only
Bits 7-4. RAS#-active to RAS#-active
or auto refresh of the same bank.
DRAM timing
Configuration
Read only
Bits 3-0. This filed should be loaded
with a 4-bit value equal to the
maximum asynchronous latency in the
DRAM read round-trip loop.
Chapter 4: BIOS Setup 102