Thank you very much for these kind words. 😊
I tried to arrange the wires as tidy as possible, thus making the whole thing to look way too complicated I guess.. ^^
But I really have to thank you. I always hoped I could build something like this myself someday and
I'm really glad I finally had a reason to try to do so.. Overall, it was a "ruminant" experience I'd say.
And it astonishes me that it already works in its current state!
Speaking of this, I've already dumped a few ROMs of several video cards (esp. my Trio32/64's and Virge's ROMs).
And thankfully, most of them match the results of my USB programmer so far (verify ok). 😀
But I have got the feeling there are still things to fix and improve (adding some more caps maybe).
So please don't be disappointed if it doesn't work with the 2764 right away.
- I've created for you another dump of the CGA ROM, but its content differs significantly from the inital file.
And the size is also different, probably doubled. Hope that's okay.
And I'm also curious to what causes this strange behavior of the 2764!
It's not the kind of chip I'm used to. It is higher than a normal one (see picture).
Maybe it was an early high-capacity model ? This would at least explain the height. If it was high-end at the time,
the manufacturing was surely more difficult and they needed more space (heat problems, larger core).
But that's just guessing of mine. The date on the label says 1985, so it's at least possible it was a leftover from an old stock.
Or maybe its appearance was just normal for a chip from the east (sov. chips often also looked different than their western counterparts).
However, this still doesn't explain the issues. Maybe it's just faulty (the floating gates, maybe ) or suffers bit rot ?
And if the chip was indeed somehow faulty, then why does it work so fine on the graphics card ?
Maybe the original datasheet can help us to find out.. The EPROM is a "M5L2764K -2" and was made by Mitsubishi.
It took me some time to realize this. When I compared the logo on the chip with some companies' logos I initally
ended up with Matsushita Eletronics Corp. (they used the same logo at some point, funny).
Luckily, I've found the right one later on, because both companies were present in my USB programmer's chip database
when I searched for a "M5L2764" entry.
I really hope we get this mystery solved. If not, I'll try to get hold on another EPROM programmer next month.
Anyway, I don't feel comfortable to post too much in this nice thread without providing any usable results.
"Time, it seems, doesn't flow. For some it's fast, for some it's slow.
In what to one race is no time at all, another race can rise and fall..." - The Minstrel
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