Looking for 1Mx8 EPROMs (27C080 or 27C801)

Andrew Lynch lynchaj at yahoo.com
Sun Jun 8 10:00:06 CDT 2008

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Glen wrote:
> Digi-Key lists the M27C801-100F1 @ $7.12 each for q >= 10.
> That's not too far away from $5 ...

Though it's an OTP, so as soon as you need to reprogram it once, you've
lost the cost savings.


Regarding the OTPs, I agree and am looking for the UV eraseable EPROMs.

Possibly, 27C4001 chips may work as an alternative and they are being sold
by Mr. EPROMMAN.  I'll get one soon and test it.

I would really like to avoid OTPs as the primary method to update the
software on the SBC is to download and/or create a new ROM image.

OTPs have their uses and could be a "fall back to known good" chip but the
lack of reprogrammability makes them wasteful in my mind.

During the design, I wrestled with Flash ROM versus EPROM for quite a bit.

I went with EPROM since they are unchangeable in circuit and have larger
capacity for the same 32 pin socket.

My assumption was with cheap and plentiful EPROM programmers (search for
Willem on eBay ~$20) that practically everyone interested would have one.

Flash ROM has its advantages but requires more advanced software for in
circuit reprogramming.  The software would have to be written too.

Some Flash ROM chips have "code protect" modes as well which make them more

I am considering some possible modifications to the design using shim
sockets to convert to Flash ROM as they are very cheap and readily

The best design would be flexible and accept either chip but there are
differences in pin outs that prevent "drop in" replacements from working.

I have already tested a variety of Flash ROM devices with no luck so far.

The best solution though, IMO, would be a low cost source of used
27C080/27C801 chips.  

There has to be someone out there with lots of surplus used 1Mx8 chips
laying around.  They were common as dirt just a few years ago.

Thanks and have a nice day!

Andrew Lynch 

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