I have used RCM5700 with R5000 to output data at the maximum possible rate. I am using DMA to the AUX I/O (port A = data, B = addr, E = control strobe). After optimisation (DMA prio = high, no CPU cycles in between, CPU clock doubler on, DMA length = 64 bytes) I measured the following rate: There are always two bytes (due to 16 bit access?) in a 100ns interval (10 MHz). The next packets (within the same DMA transfer) come with a period of 800ns after the first one, i.e. every 800ns I can get a data transfer of 2 bytes, effectively yielding 400ns = 2.5MHz max.
- Is this all I can get? I need approx. 6 to 8 MHz.
- What is the interval for? fetching new data from memory? Wait states?
- Can I get any faster, or is this the limit?
BTW, the amount of data is 80kBytes in total. I measured the DMA only, so no CPU overhead expected.
HCC