EPROM question....

Robran68

Well-known member

Donor 2011
Joined
Feb 17, 2008
Messages
3,619
Reaction score
36
Location
Fraser, Michigan
I have a Turbo Out Run board I'm trying to fix and it has 3 bad EPROMs. All 3 are 27512's and I was wondering if I can use 27256's instead?? Will these program and work correctly on the board? The ROM images are 63KB so should easily fit. Only reason I'm doing this is because I have a bunch of 256 chips and no extra 512's.

Thanx!
 
The 512 and 256 refer to the number of k bits the chip can hold. Since the data is stored in 8 bit words, you need to divide by 8. That means a 27256 can only hold a (256/8) = 32k file. A 27512 can hold a 64k file. The short answer is no.
 
It's pretty rare for the EPROM itself to go bad - usually the data just gets corrupted. You should be able to erase and reprogram.

If you really need some 512's, let me know - I can send you a couple.

-Ian
 
It's pretty rare for the EPROM itself to go bad - usually the data just gets corrupted. You should be able to erase and reprogram.

If you really need some 512's, let me know - I can send you a couple.

-Ian

These particular EPROMS don't have a window on them. Not sure if I can erase them or not.
 
sounds like otp eproms. (one time programmable). In theory, you can program the same data back to the eprom without erasing it, as long as the data is the same as what was originally there. I've had it work a few times, but not often. Nothing to lose by trying though, you might get lucky.
 
sounds like otp eproms. (one time programmable). In theory, you can program the same data back to the eprom without erasing it, as long as the data is the same as what was originally there. I've had it work a few times, but not often. Nothing to lose by trying though, you might get lucky.

Ok I will try that thanx! If not I might need a few 512's soon and take ya up on that offer RetroHacker!
 
Back
Top Bottom