Could you summarize the thread as to why they are not all 30MHz? Parts shortage? I can't imagine anyone wanting a 25MHz if a 30MHz version was available.
It's not hard you know to just read the thread... Anywayz...
Jens said:ACA630 is also available with 30MHz and 64M ram.
We're keeping the temperature low by under-clocking a 33MHz CPU (with full MMU) to 30MHz. The memory controller was kept at the same pace with a 2-1-1-1 burst, so the speedup over the 25MHz version is really linear. Sysinfo shows 7.24 MIPS / 6936 Dhrystones.
...the SD-Ram controller is clocked twice as fast as the CPU, that's why we need a 50MHz crystal on the board. I'm serious about not overclocking, as the 50MHz give precisely the timing that the memory chips can handle: 20ns from row-open to column access, and also 20ns from precharge to row-open. The CPU may not fail at higher speeds, but the memory will.
...The divider is in the CPLD, where all the async mainboard interface and the SD-Ram interface is located. Also, it is critical that the SD-Ram controller and the CPU run in sync - a simple clock-doubling for the CPU would not work at all. As I mentioned earlier for the ACA1230, the two cards (28MHz and 56MHz) look the same, but the CPLD contents are substantially different. It's a whole new development.
I really can't help anyone who wants to do weird things to his accelerator. I shouldn't even start to get into this much detail. If you haven't developed an accelerator yourself, you can't do it. I'm not just saying this to protect myself from too much customer support work. I am doing this to protect you from a failure waiting to happen, unless you have at least the same knowledge as Oliver and I have.
Anyone knows where could I download ACA tune tool??
http://www.icomp.de/t/bin/ACATune_V10.lha
