The datasheet for the AT91RM9200 states the maximum frequency is slightly higher than 200MHz and the 200MIPS reference is for 180MHz.

Is this chip completely stable at 200MHz with an 80MHz interface to SDRAM (which I think I read was possible)? Thanks.


Michael

Hi,

180MHz is teh maximum frequency in worst case (85°C). In typical condition (25MHz), you can run the device at 200MHz. Regarding, the SDRAM, 60MHz is the maximum in worst cae again, 80MHz in typical condition...

Rgds
JP

Thank you for the response. I have a couple more questions, if you don't mind too much. I'm trying to determine if this processor has the data throughput capability and instruction speed for my application.

- Using 32-bit SDRAM at 60MHz, is there an easy way to determine how long it takes to read one 32-bit instruction (ignoring I-caching)? Of course it depends on individual chips for RAS/CAS but there are common settings(I have some 100MHz chips on hand that I will use).
- On average, what kind of instruction rate can be expected using the caches? Just ballpark, its not possible to know exactly.
- Can the 16KB Fast SRAM be used to execute code out of? I imagine it is 0WS memory which may come in handy for my application.


Thanks again for the help. Maybe you have some experience with the results I am looking for but I don't expect actual calculations, maybe you have some written specs already? Thank you!


Michael

Hi MWeston

Yes you can use the 16k SRAM for code. I place all my "fast" code in here (as well as stack and heap) and it does make a difference.

I'm sure you can work out how many cylces it takes to read SDRAM, I have seen a post in here that details it. Search under I/O performance (I think).

However please use I-cache and D-cache. They make a huge difference to SDRAM performance (in fact whole chip performance). You have 16k of cache and the read write time of the SDRAM sort of becomes less important. Locking variables into cache also improve performance.

I know that makes it very difficult to benchmark the chip. I do realtime video manipulation on mine, that might be a guide.

Simon.

Thanks for the tips Simon. I have searched this site for the SDRAM stuff, but didn't find anything that could help me specifically.

I did read some of your other posts about video processing and 10MB/s would be more than I need so this chip should do the trick for me. I need a guaranteed 1.1MB/s times two (read from one source and write to another) with a bit of data manipulation in between.


Michael