AMD gx1memtim maxperf free download

File name gx1memtim_maxperf.pdf

AMD GeodeTM GX1 Processor Memory Timings for Maximum Performance 1.0 Scope There are many variables and trade-offs that the system 2.2 SDRAM Clock Considerations designer must consider to achieve maximum memory per- The SDRAM clocks generated by the GX1 processor are formance in a design. This document provides memory not perfectly periodic; some clock periods can be slightly timings and the factors affecting them for systems based longer and others slightly shorter. The memory settings on the AMD GeodeTM GX1 processor. must account for these shorter periods. This jitter is the In addition to this document, the system designer should reason for requiring PC133 memory devices for speeds of also refer to the application note AMD GeodeTM GX1 Pro- 90 MHz and higher. cessor PC133 Layout Recommendations for recom- mended layout methodologies and guidelines. Following 2.2.1 Loading Restrictions Between 78 and those guidelines is of utmost importance for designs sup- 100 MHz porting processor core and memory speeds of 300/100 To support speeds between 78 and 100 MHz, loading must MHz and 333/111 MHz. Designers who do not follow those be restricted to a maximum of 16 devices. There are four recommendations are at high risk of producing an unstable SDRAM clocks generated by the GX1, each of which must motherboard, with the only corrective action being a rede- be restricted to a maximum of four loads each, to support sign. speeds over 78 MHz. These 16 loads can take the form of Note: This is revision 4.0 of this document. The change one DIMM, two SODIMMs, or discrete memory. Total mem- made from revision 3.0 (dated September 2000) is ory achieved by 16 devices is a function of the SDRAM the additional timings and data to support a GX1 technology used. 333 MHz based system with a memory speed of 111 MHz. 2.2.2 Loading Restrictions at 111 MHz To support the 111 MHz speed, loading must be further restricted to a maximum of eight devices. These eight 2.0 Discussion loads can take the form of one SODIMM, or discrete mem- ory. Total memory achieved by eight devices is a function of The GX1 processor has a very flexible memory architec- the SDRAM technology used. The four SDRAM clocks ture in that it can be configured to support many different generated b