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3.085 bytes |
Service Hints & Tips |
Document ID: PFAN-3NRVK9 |
TP 770 - Memory configurations with 64 MB DIMMs
Applicable to: World-Wide
Problem:
Full extended memory may not be available in 770 ThinkPads.
Configuration:
64 MB EDO DIMM in Slot 2 of extended memory card.
Note: This Hint does not apply to the ThinkPad 770E and ED as these systems only use SDRAM memory
Symptom:
The memory count in POST will be lower than it should be by half of the amount of the DIMM in slot 2.
Detail:
The limitation arises from the fact that Thinkpad 770 supports up to four banks of memory. One bank is for system board memory, two banks for Slot 1 (as referred to on page 3-4 of the User's Guide), and one bank for Slot 2 of the extended memory card. DIMM memory expansion cards may be arranged as a 1 bank or 2 bank design. Therefore, any two bank DIMM that is placed in slot 2 will have only half (1 bank) of its memory recognized and useable. Currently, this limitation only affects some 64 MB RAMs (those that have a 2 bank memory arrangement). However, this may be the case with some 128 MB RAMs (when available).
Solution:
Place the 2 bank Memory Option (64 MB DIMM) in slot 1 since this slot will support a two bank DIMM. If the customer wants to install two 2-bank DIMMs, the system will only use half the memory on the DIMM in slot 2. The 770 product announcement mentions that current memory options allow memory expansion up to 160 MB by adding 2 64MB SDRAM DIMMs. The IBM SDRAM DIMM options are arranged as single bank chips, so this does indeed work. If the customer is not sure of the bank arrangement of their memory, they should contact the memory vendor.
Additional Information:
IBM Thinkpad Options
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SO DIMM |
Part Number |
Number of Banks |
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64 MB EDO |
76H0268 |
2 |
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64 MB SDRAM |
76H0295 |
1 |
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Search Keywords |
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Hint Category |
Memory | |
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Date Created |
13-11-97 | |
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Last Updated |
06-05-98 | |
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Revision Date |
30-04-99 | |
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Brand |
IBM ThinkPad | |
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Product Family |
ThinkPad 770 | |
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Machine Type |
9548, 9549 | |
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Model |
Various | |
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TypeModel |
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Retain Tip (if applicable) |
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Reverse Doclinks |