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Blank Eproms

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Denny:
Hi,
Went to buy some blank eproms and wanted to get some M27C020 and some M27C040 but they all had numbers like -90DI or -120Di or -150DI or -95DC or -120DC  behind them like  (M27C040-150DI ?? )  which ones do I need for my Bally and IGT machines ?? :Scratch-Head:
Denny

rokgpsman:

--- Quote from: Denny on December 15, 2014, 05:04:21 PM ---Hi,
Went to buy some blank eproms and wanted to get some M27C020 and some M27C040 but they all had numbers like -90DI or -120Di or -150DI or -95DC or -120DC  behind them like  (M27C040-150DI ?? )  which ones do I need for my Bally and IGT machines ?? :Scratch-Head:
Denny

--- End quote ---

Those numbers & letters are called suffixes and they mainly refer to the speed spec on the chip, plus other things like operational temperature limits, type of chip enclosure (plastic or ceramic), etc. The temp limits are not a problem for stuff in home use as it isn't going to get extremely cold or hot. But the speed rating is important since your MPU board runs at a certain speed (frequency) and it needs chips that are that fast or faster. The speed rating refers to how fast the eprom responds when the cpu requests data and that speed is expressed in nanoseconds, so a -90 is a 90nsec chip, a -120 is a 120nsec chip. The lower the number after the "-" dash the faster the chip is, since time is the inverse of operating frequency. So a -90 is a faster chip than a -120. The cpu chip on your MPU board runs at a certain speed determined by its master clock signal and needs all the chips connected to it to be as fast or faster. If you buy eproms that are capable of running faster it doesn't hurt anything, they are still going to be run at the speed of your MPU board when you install them. It's like putting Indy race tires on a Ford Taurus, the tires are capable of more but the Taurus will still only run them at a normal car speed. 

Sorry I'm not familiar with your particular machine but maybe you can look at your old eproms to see what the speed rating on them is. Or others here that are familiar with your particular machine can likely tell you. If the cost is about the same I'd get the -90 or -100 eproms, it is very likely they would be fast enough.

The speed rating on the eprom is its max speed, it can be run at a slower speed, so installing eproms that are rated faster than needed does not speed up your machine, they will still run at whatever the MPU board speed is since they are connected to the same master clock signal the cpu chip is.

rickhunter:
You need 120 or better (the lower then number the better, so -90 -100 etc)

Denny:
Hey, Thanks you guys...So do I need the 90 DI  or the 95  DC ??

rickhunter:
The letters after the number are not important for slot applications.  You can buy either one.  I would buy the fastest I can get my hands on.  I typically buy 90's for my needs, but when I can't find any, 120's have worked in all my slots (S2000's, S+, Bally Alpha, WMS 55x, WMS BB1).

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