lars@myab.UUCP (lars) (10/14/86)
Keywords: >> Using the untranslated addresses as the RAS addresses and doing the MMU >> address translation before the column addresses are needed for CAS sounds >> pretty general to me. There is interesting problem here. If the processor uses burst mode you can not use the untranslated part of the address as row adress. This is because the burst uses adress bits 3 and 4 as the low bits in the column adress. There might be a sollution to this. If the MMU page size is 4096 bytes, 12 bits in the adress is untranslated. Of these, 2 bits are used for byte select (I think this is true for 68030). Remains 10 bits. 2 bits are used for the burst mode. Remains 8 bits. In other words, the row adress must not be bigger than 8 bits. This sets the max size of memories to 64 kbits, or maybe 64k x 4 bits. By the way, NS32332 uses burst mode. We have used this burst mode in our computer since june. -- ______________________________________________________ Lars Pensjo {decvax,philabs}!mcvax!enea!chalmers!myab!lars