QL RAM extension

1 QL RAM extension Sinclair"s QL has as standard a 128 K RAM, which sounds like a lot in com- parison with most 64 K machines. Unfortunately, the software writers, in the knowledge that there is more than enough memory, have been rather wasteful in their work, so that at the end of the day, there is not all that much more in the QL than in the 64 K machines. So, you need more memory... The accompanying circuit is an appli- cation of the TMS4500A as RAM extension for the 68008. This chip can drive a maximum of 128 K dynamic RAM and provides virtually everything: multiplexing of the address lines, RAS, CAS, and REFRESH. The memory ICs are 64 K x 1 (128 or 256 refresh are both permitted) and have a speed of better than 150 ns. Since the QL uses a clock frequency of 7.5 MHz rather than the normal 7-54 elektor july/august 1985 s 32a n U 32b LJ Cl 16V is 0V lb • RESET L 0 12b ASL 0 6b A0 0 22b Al 024b A2 026b A3 0 24a A4 0 23" A5 0 22a A6 02" Al 0 20a A8 0 16o A90-1-8 A10 0 17" 16a ...