VT8601 Via, VT8601 Datasheet - Page 49

• Manufacturer Part Number: VT8601
• Description: Slot-1 / Socket-370 PCI North Bridge
• Manufacturer: Via

Device 0 Offset 6C - SDRAM Control ............................. RW
Revision 1.3 September 8, 1999
Rx6B[0] Rx64-66[1-0] Rx68[7-6] Remark
7-5
2-0
4
3
0
1
1
1
1
7HFKQRORJLHV ,QF
Reserved
CKE Configuration
Fast AGP TLB lookup
SDRAM Operation Mode Select
:H &
:H &R R QQHFW
000 Normal SDRAM Mode ..........................default
001 NOP Command Enable
010 All-Banks-Precharge Command Enable
011 MSR Enable
100 CBR Cycle Enable (if this code is selected,
101 Reserved
11x Reserved
0
x
1
0
1
01 or 10
01 or 10
01 or 10
QQHFW
00
00
Rx6B[4]=0
Rx6B[4]=1
Rx6B[4]=0
Disable ...................................................default
Reduce the lookup time from 4T to 2T
(CPU-to-DRAM cycles are converted
to All-Banks-Precharge commands).
CPU-to-DRAM cycles are converted to
commands and the commands are driven on
MA[13:0]. The BIOS selects an appropriate
host address for each row of memory such that
the
MA[13:0].
CAS-before-RAS refresh is used; if it is not
selected, RAS-Only refresh is used)
right
........................................ always reads 0
00
00
00
01
11
commands
RASA = CSA, RASB = CSB,
CKE0=CKE0, CKE1 = CKE1
RASA = CSA, RASB = Float,
CASB = Float, MAB = Float,
CKE0 = CKE0, CKE1 = CKE0
RASA = CSA, RASB = CSB,
CKE3-2 = CSA7-6
CKE5-4 = CSB7-6
CKE1 = GCKE (Global CKE)
CKE0 = FENA (FET Enable)
Only allow sub-bank of a SDRAM
Allow mutliple sub-banks across
Non-page mode, every access starts
from precharge-active cmd
Only one page active at a time
(recommended setting)
bank active at a time, # of subbank
depends on Rx64-66<1:0>
different SDRAM banks active, but
if EDO is accessed, all SDRAM
pages will be closed
Allow maximum 8 pages of
SDRAM, EDO opened
are
generated
on
-43-
Device 0 Offset 6D - DRAM Drive Strength................... RW
6-5
7
4
3
2
1
0
Reserved
Delay DRAM Read Latch
MD Drive
SDRAM Command Drive Strength
(SRAS#, SCAS#, SWE#)
MA[2:13] / WE# Drive Strength
CAS# Drive Strength
RAS# Drive Strength
00 Disable................................................... default
01 0.5 ns
10 1.0 ns
11 1.5 ns
0
1
0
1
0
1
0
1
0
1
6 mA .................................................... default
8 mA
16mA .................................................... default
24mA
16mA .................................................... default
24mA
8 mA .................................................... default
12 mA
16mA .................................................... default
24mA
........................................always reads 0
Device 0 Bus 0 Host Bridge Registers
VT8601 Apollo ProMedia