High performance dynamic ram interface
First Claim
1. A DRAM memory subsystem capable of minimum wait state accessing by a high performance device accessing outputting a series of row and column addresses for data to be accessed comprising:
- (a) a DRAM comprised of rows and columns and operable in a static column mode in response to address requests asserted at RAS and CAS inputs thereof; and
,(b) access optimization logic means operably connected for receiving a first row and column address as output by the device, for asserting said first row and column address at said RAS and CAS inputs, for receiving a second row and column address as output by the device, for changing the column address being asserted at said CAS input to correspond to said second column address, for checking said second row address against said first row address, and for reasserting said second row and column address at said RAS and CAS inputs if said second row address is not the same as said first row address.
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Accused Products
Abstract
A method and associated apparatus for accessing a plurality of DRAMs in the static column mode by a high performance instruction processor to provide minimum wait state accessing thereby. The method comprises the steps of, having the instruction processor emit each instruction address as an address containing a bank number field, a row address field, and column address field; providing a table for storing a set of open pages being the current row address for each bank where a bank is associated with a respective one of the plurality DRAMs; for each instruction address emitted from the instruction processor, determining whether there is a match between the row address stored in the table and the row address emitted from the instruction processor employing the bank number as an index into the table of open pages; if the two addresses match, continuing the memory access to the indicated bank in a continuing static column mode; and, if the two addresses do not match, overwriting the old address for the indicated bank in the table with the new row address and continuing the memory access by beginning a new static column mode access to the indicated bank. In the preferred embodiment, the method includes, as necessary, aborting the access in progress if the two addresses do not match prior to beginning the new static column mode access to the indicated bank and advising the instruction processor that the access in progress is being aborted and being begun again.
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Citations
13 Claims
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1. A DRAM memory subsystem capable of minimum wait state accessing by a high performance device accessing outputting a series of row and column addresses for data to be accessed comprising:
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(a) a DRAM comprised of rows and columns and operable in a static column mode in response to address requests asserted at RAS and CAS inputs thereof; and
,(b) access optimization logic means operably connected for receiving a first row and column address as output by the device, for asserting said first row and column address at said RAS and CAS inputs, for receiving a second row and column address as output by the device, for changing the column address being asserted at said CAS input to correspond to said second column address, for checking said second row address against said first row address, and for reasserting said second row and column address at said RAS and CAS inputs if said second row address is not the same as said first row address. - View Dependent Claims (2, 3)
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4. The method of operating a DRAM memory subsystem having a DRAM comprised of rows and columns and operable in a static column mode in response to address requests asserted at RAS and CAS inputs thereof to provide minimum wait state accessing by a high performance memory accessing device outputting a series of row and column addresses for data to be accessed comprising the steps of:
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(a) receiving a first row and column address as output by the device; (b) asserting the first row and column address at the RAS and CAS inputs; (c) receiving a second row and column address as output by the device; (d) changing the column address being asserted at the CAS input to correspond to the second column address; (e) checking the second row address against the first row address; and
,(f) reasserting the second row and column address at the RAS and CAS inputs if the second row address is not the same as the first row address. - View Dependent Claims (5, 6)
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7. The method of accessing a plurality of DRAMs in the static column mode by an instruction processor to provide minimum wait state accessing thereby comprising the steps of:
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(a) having the instruction processor emit each instruction address as an address containing a bank number field, a row address field, and column address field; (b) providing a table for storing a set of open pages being the current row address for each bank where a bank is associated with a respective one of the plurality of DRAMs; (c) for each instruction address emitted from the instruction processor to effect a memory access in a static column mode, determining whether there is a match between the row address stored in the table and the row address emitted from the instruction processor employing the bank number as an index into the table of open pages; (d) if the two addresses match, continuing the memory acess to an indicated bank in a continuing static column mode using the row and column addresses as presently asserted from the instruction address emitted from the instruction processor; and
,(e) if the two addresses do not match, overwriting the old address for the indicated bank in the table with the new row address and continuing the memory acess by beginning a new static column mode access to the indicated bank by reasserting the row and column addresses from the instruction address emitted from the instruction processor. - View Dependent Claims (8, 9)
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10. In a DRAM memory subsystem having a DRAM comprised of rows and columns and operable in a static column mode in response to address requests from a high performance memory accessing device outputting a series of row and column addresses for data to be accessed, the method of operation to provide minimum wait state accessing comprising the steps of:
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(a) beginning each new access request from the device in a continuing static column mode access by only changing the column address; (b) checking the row address being employed in the continuing static column mode access against the row address of the new access request; (c) continuing with the current continuing static column mode access if the row addresses are the same; and
,(d) terminating the current continuing static column mode access and beginning a new static column mode access with the row and column addresses of the new access request if the row addresses are not the same. - View Dependent Claims (11, 12, 13)
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Specification