Dumb question - can a 2716 EPROM substitute for a 2708?

Tornadoboy

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Dumb question - can a 2716 EPROM substitute for a 2708?

I've got an board conversion experiment going on and one of the EPROMs I have to replace is a 2708, which I don't have a programmer that can handle it, so I was wondering if once it's programmed can a 2716 EPROM work in place of the 2708?
Attached is the pinouts for both chips, they're very close but there are a few differences, and I don't know what some of the listing mean.
 

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Dumb question is right. Never mind, I answered the question myself as A10 is clearly in the wrong place and that in itself would kill the idea.

My bad. That's what I get for being too trigger happy to post a question. :(
 
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Yes and no.

Pin 18 needs to be grounded on the 2716. You program the lower half of the chip and then tie pin 19 to ground using a 330 ohm resistor. This forces the upper address pin low so the CPU can only access the lower half of the EPROM.

You may be able to get away with grounding A10 without the resistor, but I wouldn't recommend it. I ran into problems with that on my Colecovision dual BIOS kits in that some EPROMs tie the address lines high (27128/c128 chips from Hitachi and AMD gave me fits!) internally and will generate massive amounts of heat then fail if you short the address lines directly to ground.

Also, the odd voltages on the 2708 MUST be removed from the 2716 or it will fry.

Check the data sheet to see if you need to tie the PGM pin high or to ground for normal operation.

RJ
 
Correct it's not a drop-in replacement, but it's pretty easy to convert a board from weirdo 2708 to the more common 2716/2732. And since those chips are 2x or 4x larger you can often rework the board at the same time to use fewer chips/sockets.

I wrote up some of the details in this thread: Using 2716, 2732 on Space Invaders
 
Hi, Is that a typo?

My appologies, miss-read that.

So you're removing the old 8x2708's EPROMs and replacing them with 8x2716 EPROMs and just using the lower half of each 2716; by tying the address line (AD10) of each 2716 low. Thus making a 1K code block in the lower half of each EPROM, and skipping the upper half, the direct result of tying the address bit (AD10) LOW. I hope this is correct?

Ro
 
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