74S409 (was Re: Anyone have a data sheet on the MC3242?)

--- Ben Franchuk <bfranchuk(a)jetnet.ab.ca> wrote: We used the 74S409 for our 64K and 256K DRAMs on COMBOARDs. I have enough to last several lifetimes, if anyone wants to play with one. We learned the hard way that 33 Ohm resistors were required inline with the CAS and RAS lines to minimize undershoot, but other than that, they are rock-solid. A 74S409 went on every COMBOARD after the COMBOARD-I (which had 32KW of 2114 SRAM). I think we typically put 16-18 chips per board (the COMBOARD-II has parity) - it worked out like this... COMBOARD-II - 128KB (4164 x 18) COMBOARD-Q - 512KB (41256 x 16) COMBOARD-BI - 2048KB (44256 x 16) The reason why I mentioned the number of chips is that the inline resistors are "tuned" to the load of the number of DRAMs they have to drive. We had a cancelled project with a 68000 + 68451 in a desk-top box with up to 32 serial ports and 512K - 2048K of 4164s. The number of populated banks affected the values of the resistors. -ethan __________________________________________________ Do You Yahoo!? Yahoo! - Official partner of 2002 FIFA World Cup http://fifaworldcup.yahoo.com