The DM6446 DDR2 controller has: 162 MHz max speed max 2 transfer per clock cycle 4 bytes per transfer
so the max (teorical) bandwidth is 162 x 2 x 4 = 1296 Mbytes/sec All that is true in the ideal world! Real estimates from TI tell 1240 MBytes/sec, so there is a scaling factor 0.957. The DM355 DDR2 controller has 270 MHz max speed max 2 transfer per clock cycle 2 bytes per transfer resulting in a max (teorical) bandwidth of 270 x 2 x 2 = 1080 Mbytes/sec Now, If we assume a similar scaling factor we obtain 1034 Mbytes/sec As regards the problem of simultaneous playing and recording of media files one should take into account also the SD interface (hardware transfer bandwidth), media format (mainly time resolution and space resolution) and the additive load represented by concurrent tasks. Gabriele Da: Panchy Rivas [mailto:[EMAIL PROTECTED] Inviato: giovedì 30 ottobre 2008 15.15 A: Gabriele Filosofi Oggetto: RE: Custom DM355 PCB Thanks for the help Gabriele. So that is a major difference between the DM355 and the DM6446. Do you know what the bandwidth is on the DM355 and DM 46446. Will the DM355 have enough bandwidth to record to SD card and play a different file at the same time. Thanks Panchy Rivas From: Gabriele Filosofi [mailto:[EMAIL PROTECTED] Sent: Thursday, October 30, 2008 10:04 AM To: Panchy Rivas Subject: R: Custom DM355 PCB Gabriele Da: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] Per conto di Panchy Rivas Inviato: giovedì 30 ottobre 2008 14.51 A: [email protected] Oggetto: Custom DM355 PCB I plan on making a custom DM355 board and have a few questions. 1) When we first populate the PCB how do we get Uboot, kernel, software on it? 2) What exactly does the GEL file do (do we need it) and do you need CCS to load it? 3) Side question - is the DDR2 memory on the DM6446 faster because of 32bit width compared to DM355? Both transfer rate and bus width affect the transfer bandwidth: Total bandwidth = transfer rate x bus width. Doubling bus width doesn't affect the transfer rate, but it doubles the transfer bandwidth. 4) I heard there was a drop-in gerber file for the DDR2 memory PCB layout? I already read the DDR2 layout docs but wanted the actual layout. Thanks Panchy Rivas
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