Normally these chips which are re-programmable, go for $5 each as seen in other eBay listings. And I had previously bought a few at that price point. However they're no longer in production, so what you get are NOS ones that someone still has a stash of tucked away. What makes them really nice is that you don't have to have a UV light source to erase them, since it's done electrically instead. Making for a much better and faster programming cycle.
Now I can get OTP (One Time Programmable) 512K EPROMS by Microchip/Atmel for about $2.50 in single quantities, and they are in current production. But being a one time programmable device means that you better get it right the first time, and be happy with it forever. However unless you plan on investing in a chip programmer such as the TL866 Plus, this may not be many peoples cup of tea. Luckily for the 576NUC+ there really is no need, since The Brewing Academy will be selling them with pre-programmed ROMs when they go into production.
The 576NUC+ system ROM contains two different Operating Systems, two versions of BASIC, and two games. It could be handled by a OTP device as mentioned, and for most people that'll probably be OK. But for a few of you who love to be able to customize your system, a re-flashable ROM would be desirable, hence the reason I was looking for an inexpensive and readily available source of these.
So I went in search for that cheaper EEPROM, once again going back to eBay. This time I found another seller for the SST EEPROMS that was advertising a deal that I knew was too good to be true, but part of me was game to find out for sure since the seller was only asking for about $1.00 a piece.
Here's that eBay listing.
Now I can get OTP (One Time Programmable) 512K EPROMS by Microchip/Atmel for about $2.50 in single quantities, and they are in current production. But being a one time programmable device means that you better get it right the first time, and be happy with it forever. However unless you plan on investing in a chip programmer such as the TL866 Plus, this may not be many peoples cup of tea. Luckily for the 576NUC+ there really is no need, since The Brewing Academy will be selling them with pre-programmed ROMs when they go into production.
The 576NUC+ system ROM contains two different Operating Systems, two versions of BASIC, and two games. It could be handled by a OTP device as mentioned, and for most people that'll probably be OK. But for a few of you who love to be able to customize your system, a re-flashable ROM would be desirable, hence the reason I was looking for an inexpensive and readily available source of these.
So I went in search for that cheaper EEPROM, once again going back to eBay. This time I found another seller for the SST EEPROMS that was advertising a deal that I knew was too good to be true, but part of me was game to find out for sure since the seller was only asking for about $1.00 a piece.
Here's that eBay listing.
About 2 weeks after my purchase I received the EEPROMS with all 20 pieces appropriately packaged in several standard IC anti-static plastic tubes. So far so good.
I then proceeded to plug them into my trusty TL866 Plus programmer and initially tried to flash them with the 64KB system ROM image for the 576NUC+, at which point, no real surprise they all failed one after the other.
JK Parts Flash Test
Next I tried to erase a few of them, and once again no dice with the same error. So I tossed in a known to be good chip, and it programmed without issue. But then I noticed a crucial difference in the chip ID. The one from JK Parts showed 0X DA 08, whereas the working chip was 0X BF A4. So I checked my stock of good chips, and all of them returned the same ID (0x BF A4). Next I checked several of the chips from JK Parts, and they all had that different chip ID of 0X DA 08. Obviously the JK Parts chips were not really SST 27SF512s but something entirely different (what are they really??? - initially I didn't know - hint: see note at the end of this blog post for the answer).
Known Good Chip Flash Test
So with that revelation, I scrutinized the appearance and labeling on the top of what I will now call a 'REAL' 27SF512, and compare it to a 'FAKE' 27SF512 better known as the chips I purchased from JK Parts on eBay. As can be seen below it's rather obvious that something is amiss with the FAKE chip's labeling. For one the numbering is way too crisp and clean, yet the SST label looks a bit rough around the edges. And although you can't really see it all that good in the photo, the depth of the indentation is much more shallow on the FAKE chip, as if someone sanded off some of the material (which they probably did in order to prep it for the new label). The printing is resistant to acetone, which was the strongest solvent I had on hand, and it might even be etched like the original would be.
So what's on the bottom of the REAL chip? Let's find out.
Yep that looks like something one would expect. Now let's check out the bottoms on those FAKE chips.
Oh yeah... that probably shouldn't look like that. Did the seller have a picture of the chip bottom on his listing? No certainly not. Apparently they couldn't be bothered to sand off and reprint the bottom of the chips like they had obviously done to the top side. At this point it was pretty clear that these were not genuine SST 27SF512 EEPROMs that I had gotten from JK Parts. But what could I do since the seller clearly stated "No Returns" on his listing.
This story has a happy ending...
Thanks to a AtariAge member Mr Robot's sleuthing skills, he matched the FAKE chip ID to a Winbond W27C512 EEPROM. And when I plugged those parameters into the XG Pro TL866 Plus programming app, everything fell into place allowing me to do multiple re-flashes of the chip as seen below.
This story has a happy ending...
Thanks to a AtariAge member Mr Robot's sleuthing skills, he matched the FAKE chip ID to a Winbond W27C512 EEPROM. And when I plugged those parameters into the XG Pro TL866 Plus programming app, everything fell into place allowing me to do multiple re-flashes of the chip as seen below.
So long story short, JK Parts sold me a relabeled Winbond W27C512 chip instead of the originally sought after SST 27SF512 I ordered. Both chips are EEPROMS, and they can both be repeatably re-flashed and erased. So bottom line I still ended up with a good deal that still works for my application, but I'll have to relabel the chips to avoid confusion. And now thanks to the seller's substitution I also know of an alternate chip for what I was originally looking for.
BTW, I was able to flash all 20 chips successfully as Winbond W27C512's.
However even though in the end this will work for what I need, I can't in my right mind recommend ordering from this seller without at least verifying what the heck is going on, although it's probably a case of Cha Bu Duo (aka: "close enough" - thanks to Mr Robot for that bit of insight). I won't be posting a link to that eBay auction, and I won't change the title of this blog post either, since it really is a fake, or in other words a substitution of another chip meant to fake the characteristics of the one it replaces..
- Michael
BTW, I was able to flash all 20 chips successfully as Winbond W27C512's.
However even though in the end this will work for what I need, I can't in my right mind recommend ordering from this seller without at least verifying what the heck is going on, although it's probably a case of Cha Bu Duo (aka: "close enough" - thanks to Mr Robot for that bit of insight). I won't be posting a link to that eBay auction, and I won't change the title of this blog post either, since it really is a fake, or in other words a substitution of another chip meant to fake the characteristics of the one it replaces..
- Michael
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