From: Erik M. <J.A...@it...> - 2002-01-29 16:56:17
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On Tue, Jan 29, 2002 at 04:47:54PM +0200, Abraham vd Merwe wrote: > 1. This is actually a general ARM question I guess, but this is probably the > best list to ask. If you calculate the DRAM settings using the Intel > configuration thingy (http://appzone.intel.com/hcd/sa1110/memory/index.asp) > you get values for MDCNFG, SMCNFG, MDREFR, MDCAS00, MDCAS01, MDCAS02, and > MSC0, but blob also needs MSC1 and MECR. From the SA-1110 datasheet it seems > these are using for expansion memory, etc. which is optional. Can I just set > this to anything in blob? (I set it to zero and it seems to work, but I'm > not sure if this is wise) If you don't use it, you can set it to anything. > 2. Also what should I expect to go wrong when my settings don't match the > processor speed. I worked out above settings for 206.4MHz, but it seems to > work fine for any clock speed (I tried 59.0MHz and 221.2MHz). Is this safe > or not? It's safe as long as the caches are disabled. You'll see strange lockups when the kernel starts and enables the full MMU tricks cause in that case you'll get burst access to the RAM which are much more critical to good timings. > 3. It seems that if the CPU runs at > 200MHz then the memory is accessed at > 1/4 of the core cpu speed (for 100MHz SDRAM), but if the CPU runs < 200Mhz > it is 1/2 the core cpu speed, so at 206.4MHz you get 51.6Mhz, but at > 191.7MHz you get 95.9MHz ram (almost twice as fast). Isn't it better to run > the CPU at a bit slower speed then or does the 20 odd Mhz make such a big > difference (in which case you should be running at 221.2MHz I guess). Depends on the application. We have a nice paper about that on the "Clock scaling" page on the LART website. Erik -- J.A.K. (Erik) Mouw, Information and Communication Theory Group, Faculty of Information Technology and Systems, Delft University of Technology, PO BOX 5031, 2600 GA Delft, The Netherlands Phone: +31-15-2783635 Fax: +31-15-2781843 Email: J.A...@it... WWW: http://www-ict.its.tudelft.nl/~erik/ |