AMD AMD-K6-2/500AFX Data Sheet - Page 211
Cache Organization, AMD-K6, 2 Processor Data Sheet, Write to a Sector, Between 15-16 Mbytes
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21850J/0-February 2000 Preliminary Information AMD-K6®-2 Processor Data Sheet 6. Write to a Sector-A write allocate is performed if the address of a pending write cycle matches the tag address of a valid cache sector but the addressed cache line within the sector is invalid. See "Write to a Sector" on page 187 for a detailed description of this condition. 7. Less Than Limit (WAELIM)-The write allocate limit mechanism determines if the memory area being addressed is less than the limit set in the WAELIM field of WHCR. If the address is less than the limit, write allocate for that memory address is performed as long as conditions 8 through 10 do not prevent write allocate (even if conditions 8 and 10 attempt to prevent write allocate, condition 5 or 6 allows write allocate to occur). 8. Between 640 Kbytes and 1 Mbyte -Write allocate is not performed in the memory area between 640 Kbytes and 1 Mbyte. It is not considered safe to perform write allocations between 640 Kbytes and 1 Mbyte (000A_0000h to 000F_FFFFh) because this area of memory is considered a noncacheable region of memory (even if condition 8 attempts to prevent write allocate, condition 5 or 6 allows write allocate to occur). 9. Between 15-16 Mbytes-If the address of a pending write cycle is in the 1 Mbyte of memory between 15 Mbytes and 16 Mbytes, and the WAE15M bit is set to 1, write allocate for this cycle is enabled. 10. Write Allocate Enable 15-16 Mbytes (WAE15M)-This condition is associated with the Write Allocate Limit mechanism and affects write allocate only if the limit specified by the WAELIM field is greater than or equal to 16 Mbytes. If the memory address is between 15 Mbytes and 16 Mbytes, and the WAE15M bit in the WHCR is set to 0, write allocate for this cycle is disabled (even if condition 10 attempts to prevent write allocate, condition 5 or 6 allows write allocate to occur). Chapter 7 Cache Organization 191