At 08:32 AM 1/18/99 -0500, you wrote:
>I also experienced similar problems with 2114's on several of my Sega
>G08 X-Y boards.
>I had bought a bunch from BGI (2114AL- 2 ?) and since they were faster I
>assumed they
>should perform just as well, no such luck . I also tried 2148's with no
>luck. I ended up
>talking some older 2114's off of another PCB to solve the problem. Why
>is this ? can
>anyone explain ? Clay, didn't you discuss at one time making a simple
>2114 tester ?
A reason the faster 2114 may be due to faster setup/hold times of the ram.
That is, now you have a ram chip with a faster setup time, but more
importantly in this case a faster hold time. So if the hold time is too
fast, the data out may not be on the bus for a long enough time for other
devices on the data bus. I havn't looked at the schematics, but it's
conceivable that one could replace the other devices with faster ones,
along with the faster rams, to compensate for the reduced hold times. It
should be easy enought to trace the ram data path and find which device(s)
(be they tri-state buffers, or whatever) are being affected by the reduced
hold time of the faster rams.
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a n d e r s
Received on Mon Jan 18 12:44:17 1999
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