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PostPosted: Fri Oct 12, 2018 2:28 pm 
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Joined: Fri Oct 28, 2016 12:37 pm
Posts: 46
Hi all,

I'm looking to buy some EPROMs for my homebrew projects.

I found some online (27c64 and 27c128) for my 8KB CHR ROM and 16KB PRG ROM.

The chips I found are postfixed with 120ns, 150ns, etc. Does that matter when it comes to NES chips? Is there a value I should be targetting?

Thanks


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PostPosted: Fri Oct 12, 2018 2:39 pm 
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Joined: Sun Sep 19, 2004 11:12 pm
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Location: NE Indiana, USA (NTSC)
200 ns or faster should be good enough for NES or for Super NES slow ROM. For Super NES fast ROM, you want 120 ns or faster.


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PostPosted: Fri Oct 12, 2018 3:11 pm 
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Joined: Sun Jun 12, 2011 12:06 pm
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Location: Poland
Older and smaller EPROMS (2764) tends to be slower.
When using 250ns, I had issues with graphics (but Kazzo readbacks were OK), so probably yes, 200ns or faster.


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PostPosted: Fri Oct 12, 2018 3:36 pm 
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Joined: Sat Feb 12, 2005 9:43 pm
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Location: Rio de Janeiro - Brazil
Keep in mind that you don't need chips of the exact sizes of the binaries you're programming on them, you can safely use larger chips and ground the upper address lines. So if by any chance you find chips that are cheaper, faster, etc. but are larger than what you need, you can get those too.


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PostPosted: Fri Oct 12, 2018 4:14 pm 
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Joined: Fri Oct 28, 2016 12:37 pm
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Quote:
Keep in mind that you don't need chips of the exact sizes of the binaries you're programming on them, you can safely use larger chips and ground the upper address lines. So if by any chance you find chips that are cheaper, faster, etc. but are larger than what you need, you can get those too.


Nice, thanks

Quote:
200 ns or faster should be good enough for NES


Thanks, I'll pick up some of the 120 or 150ns pairs.

Excited :D


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