Thank you, gentlemen, and that includes the respondents I did not quote above (previous digest). I really appreciate all the great information and leads. I started with Pericom (as one person suggested) as I am familiar with some of their products and worked backwards from there. It appears that they are calling the product which I want "Bus Switch". Once I knew that, there's a nice selection available on Digi-Key, although I'll check Mouser later for better pricing. The selection is not quite as nice as I'd like, because there's nothing analogous to the SN74ABT241A. The nice thing about the 241 is that it divides its eight buffers into two groups of four with independent enables for the two groups of four. Okay, that's like a 244. However, the 241 has one active high enable, and one active low enable, while both enables on the 244 are active low. So I'll need an inverter in line with one of the OE pins on the bus switches, which isn't the end of the world, but its not as elegant as the SN74ABT241A would have been. The candidates are the Pericom PI5C3244 or the TI SN74CBT3244. The speeds on these components look fast enough, the time to switch Pericom and 8 ns on the TI. I'm not certain they used the same test conditions. Minimum times are 1 ns. Both have a propagation time of .25 ns from A to B or B to A once the switch is enabled. Dwight, can you elaborate on why I'd be better off with something like '245s? I either don't understand your point, or I have not explained my intent clearly enough. I am trying to emulate the SIMM on a IIfx. The only difficulty is getting X 4 DRAM chips to look as if they have separate D and Q pins. On stock IIfx SIMMs, the data signals are not buffered on the SIMM, they come directly from the DRAM chip to the SIMM connector. On my SIMM, they will go from the DRAM chip, through a bus switch (or tristate buffer) and then to the SIMM connector. So, unless too much signal strength is lost going through the bus switch, I do not understand why I'd need a buffer there to strengthen or clean up the signal. Or are you saying that I should have a latch there to hold the signal for some time after my switch control signal goes inactive to make sure that hold times are supported? The pinout on the SN74ABT241A (buffer) and the SN74CBT3244 (switch) are the same (the PI5C3244 is also the same but comes in a smaller package) and the same packages are available. I jumped the gun and already have some SN74ABT241A on hand. So I think what I'll do is design my first set of SIMMs with the posibility of taking the OE signal for the Data Out side of the buffer/switch either directly from WE, from WE run through an inverter (WE'), or from WE AND CAS'. The inverters and AND gates are available in tiny SC70 packages (similar to SOT23). Then I can test the Buffer with WE (OE is active high) as control for Din and Dout. The Buffer with WE AND CAS' (OE is active high) as control for Dout. And the Bus Switch with WE' (OE is active low) as control for Dout. Jeff Walther