Kipper : Hi, can i just see if i understand his process right. The original kickstart file is 524288 bytes long and we need to split this file into 2 equal 262144 byte files (i like using the split files option in Total Commander). the lower portion of the split file being burnt onto U6A and the upper portion burnt onto U6B.
Because these chips are 512K is it safe to say that once we split the 512k file into 2 we can simply for instance create 2 of the lower portion 256K files and join them (Again using the join files option in Total Commander) to make a 512k file (so that the upper and lower 256k portions are the same). and then burn that to U6A.
Repeating the process for U6B so that the upper 256K portion of the original 512k file is joined with itself to create a 512K file and then burnt onto U6B
… It is kinda confusing, but is this correct ?
– Heys Kippers
yep thats exactly the way you describe it
Although, you could (if using a 27c400 or 800) put another ROM file in the upper address, you could then have a simple switch that powers up the upper address line for both chips… job done, instant kickstart switcher in two chips…
– Nope, the ROM image has to be split word-wise.
eg. If the ROM image was « AABBCCDD12345678 » you’d end up with 2 files
« AACC1256 » and « BBDD3478 »
so you are saying that the way the A1200 addresses the roms is to read the low byte on U6A, and then the upper byte on U6B. Just when i thought i had it figured out ya threw a wrench in the works.. so the 32 bit bus is reading 16 bits from U6A and the next address is 16 bits on U6B etc… etc ?
– Toni Willen : Yes, 32-bit data bus = accesses 32-bits (*) / memory cycle, first 16-bit word from other ROM/EPROM and second 16-bit word from another ROM/EPROM, simultaneously.
CD32 has single 16-bit ROM. Special case, as cheap (and slow) as possible.