Abit AT7 User Manual page 46

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Without SPD, the BIOS (or user) must make assumptions about the DIMM's parameters. Many users
have found that their system will not boot if they are using non-SPD SDRAM DIMMs. As SDRAM
and DDR SDRAM DIMM's is running at very fast clock speed and there is less room for error. An
incorrect BIOS assumption about an SDRAM and DDR SDRAM DIMM's parameters can have
serious consequences (e.g. failure to boot or fatal exception errors).
DRAM Timing:
Two options are available: By SPD or Manual. The default setting is Manual. When set to "By SPD", the
BIOS will read the DRAM module SPD data and automatically set to the values stored in it. If you set to
"Manual", the following five items will be available to let you make adjustments.
DRAM CAS Latency:
Two options are available: 2.5 and 2. The default setting is 2.5. You can select SDRAM CAS (Column
Address Strobe) latency time according your SDRAM specification.
Bank Interleave:
Three options are available: Disabled ( 2 Bank ( 4 Bank. The default setting is Disabled. Depending
on your SDRAM module structure, the 4-Way setting can offer the best performance. If you choose the
wrong setting, the computer system will not run in a stable manner. For detailed information on your
SDRAM module, please ask your SDRAM module manufacturer.
Precharge to Active (Trp):
Two options are available: 2T or 3T. The default setting is 3T.
Trp timing value (Precharge time – time from precharge command to when back can be activated).
Active to Precharge (Tras):
Two options are available: 5T or 6T. The default setting is 6T.
Tras timing value = Minimum bank active time from activate to precharge of same bank.
Active to CMD (Trcd):
Two options are available: 2T or 3T. The default setting is 3T.
Trcd timing value = RAS to CAS latency + rd/wr command delay
DDR DQS Input Delay:
Two options are available: Auto or Manual. The default setting is Auto. If you set to "Manual", then the
next item will be available.
" Input Delay Value:
This item allows you to adjust the data input strobe delay time of memory. You can key in the HEX
number into this section. The minimum number is 0000, and maximum number is 03FF.
DDR DQS Output Delay:
Two options are available: Auto or Manual. The default setting is Auto. If you set to "Manual", then the
next item will be available.
AT7
Chapter 3