Can somebody school me on type of eproms

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I was wanting to know what is the best speed of eproms to get and manufacturer. For example a 2kx8 as apposed to 256kx8. Or does it really matter. Just wanting a better understanding of eproms and what to look for in buying them.


Thanks in advance
 
I was wanting to know what is the best speed of eproms to get and manufacturer. For example a 2kx8 as apposed to 256kx8. Or does it really matter. Just wanting a better understanding of eproms and what to look for in buying them.


Thanks in advance

Which one to buy depends on which one you are replacing. Refer to part numbers such as 2716, 27512, 2532, etc. Those will designate not only size, but pinout - smaller capacity EPROMS require fewer pins.

There is not really a 'universal' EPROM that is one size fits all....
 
Which one to buy depends on which one you are replacing. Refer to part numbers such as 2716, 27512, 2532, etc. Those will designate not only size, but pinout - smaller capacity EPROMS require fewer pins.

There is not really a 'universal' EPROM that is one size fits all....

This is really what I was looking for more on an answer. 2kx8 as apposed to 256kx8 the size of the eprom. What does the 2k mean in reference to information stored on the eprom compared to 256K. So, say I am looking at a 27c16. When I look at the data sheet on my programmer it show different sizes/speed I'm guessing. What is the difference in a 27c16 with 2k verses a 27c16 256k.

thanks
 
The k you refer to is the number of addresses.

Or example a 27c16 or 2716 is 2k x 8
There are 2k (2048) addresses and each address stores 8 bits of data or is 8 bits "wide"

Therefore a 2716 is 2k x 8 has 2k addresses each of 8 bits (2K bytes)
A 2732 is 4k x 8 and has 4k of 8 bits (4K bytes) and therefore stores rice as much data
2764 = 8k x 8 = 8Kbytes

Most memories(EPROMs and rams) have 8 bits in each address but there are some that have different number of bits.

After the number is usually a minus and another number, like -250 which is the speed of the ram in nanoseconds

The C as in 27c16 means internally the chip is implemented with CMOS parts.
 
By the way there is no 2716 that has 256k addresses on that you must be reading the info wrong, all memories of a certain designation like 2716 are the same #of addresses and "width in bits" the speeds may vary tjough
 
The k you refer to is the number of addresses.

Or example a 27c16 or 2716 is 2k x 8
There are 2k (2048) addresses and each address stores 8 bits of data or is 8 bits "wide"

Therefore a 2716 is 2k x 8 has 2k addresses each of 8 bits (2K bytes)
A 2732 is 4k x 8 and has 4k of 8 bits (4K bytes) and therefore stores rice as much data
2764 = 8k x 8 = 8Kbytes

Most memories(EPROMs and rams) have 8 bits in each address but there are some that have different number of bits.

After the number is usually a minus and another number, like -250 which is the speed of the ram in nanoseconds

The C as in 27c16 means internally the chip is implemented with CMOS parts.


Thank you for clarifying that for me brzezicki. I must be reading what that manufacture offers along with the 27c16. Thats what confused me when I was reading that. Now I understand or at least I hope, lol. the only other thing I have a question one is -250 which is the speed of the ram in nanoseconds. I know they come in different speeds does that matter on when buying them. If I get a slower speed will it still operate like it should on a faster speed one. Will it hurt anything if I do that. Thats permitted if I cant get the one that was exactly on the board.

Thanks
 
The lower the speed number the better that is 100 ns is faster than 250
You can always get a faster speed than the original chip without issue, if you got a slower that could be trouble, however it depends how fast the cpu chip is running and is trying to access the memory. Honestly I don't even look at the eprom speeds for the old games when replacing. But if you want to ensure everything thing will works fine just buy same speed or faster.

Video memory is generally where you get concerned about speed on the old games
 
Not all speeds on EPROMs are in nanoseconds.

On older EPROMs such as 2708 and 2716, the number indicates speed, but not necessarily the speed in nanoseconds as it relates to the number.

This varied by manufacturer but on some a 2716-2 could indicate 200ns but on others meant 350ns to 600ns. Datasheets are your friend in most cases.

http://www.datasheetarchive.com
 
Another quick note on the math example: 2716, the 16 actually refers to 16K bits. Since the data bus is 8 bits wide, you divide 16 by 8 and get 2. Thats where 2K comes from.

This works all the way into the 27512 part numbers, then starts getting weird past that.

So, for a 27128 part, 128/8=16 its a 16K x 8 part.

Also note there are several 16 bit wide EPROMs out there as well.

Static RAM used in games is typically 4 or 8 bits wide (there are other flavors as well, but mostly those two), while dynamic RAM is usually a 1 bit part (you will usually see these ganged in groups of 8).
 
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