On Aug 31, 2005, at 11:44 AM, Jeff Walther wrote:
The pinout shows a separate data_in and data_out pin for each bit of the SIMM. In other words, it's an eight bit SIMM, but instead of simply having eight data pins Data[0:7] it has eight Data_In[0:7] and eight Data_Out[0:7] pins.
The "by one bit" DRAMs had separate input and output pins. Most users just tied them together and hooked them to a bi-directional bus. I haven't looked into this, but I always assumed that what the IIfx did was keep the In and Out busses separate so that the timing operations could be overlapped thus speeding up memory operations.
That could imply that the IIfx SIMM requires bizarre dual data ported chips, but the chip examples I've identified (thanks Bob) seem to be normal DRAM chips.
I assume the mother board has the "bizarre dual data ported chips" so the SIMMs are unique in NOT hooking the In and Out pins together :-)
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