06 February 2023, 11:29 | #1 |
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EPROM type for Amiga 3000D Rev 9
Hello,
There are several topics like these: https://eab.abime.net/showthread.php?t=49857 but they are too generic and confusing. The Rev.9 does not have a ROM-tower for example. I cannot find a decisive, non-confusing answer, to the question of "which EPROM to use on the A3000 Rev. 9 Motherboard". Can I use the AM27C400-120DC ? (Disclaimer: I legally own the A3000 v3.1.4 ROM, but the ROM Chips I got from an official vendor do not work) |
06 February 2023, 13:12 | #2 | |
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I am going to answer my own question
In the paper manual that Hyperion Entertainments ships with their ROM Chips for the A3000D, it says the following: Quote:
It also says that the U182 / U183 ROM Sockets in the A3000D are NOT compatible with 27C400 type devices. There should be nothing in those sockets on a Rev.9 Motherboard anyway. Also, do NOT use the AM27C400-150DC chips one finds on eBay sometimes. They are 150ns units and are too slow. Use only the AM27C400-120DC (120ns) variant. So there you have it. Question answered. I hope this helps someone in the future |
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06 February 2023, 13:25 | #3 |
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Or faster , -100 -80 -70 -55 all are available and useable The -xxx denotes the speed , anything -120 ( 120ns ) or faster e.g -80 ( 80ns ) are useable , possibly better because of the faster access times.
These are from the M27C400-xxx range ( it does not have to be AMD ) from ST. |
06 February 2023, 13:36 | #4 |
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For the slow ones, isn't that what J150 and J151 is for? Genuine question?
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06 February 2023, 13:56 | #5 | |
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Quote:
Of course it is very probable that most of the ROMs currently sold as AM27c400 are remarked, so there may be some experimentation required. |
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06 February 2023, 15:36 | #6 | |
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Quote:
I've been using 150ns units with the shortest possible ROM timing for many years now. So, some people just don't understand how the ROM timing works: http://www.l8r.net/technical/t-3000-jumpers.shtml Last edited by SpeedGeek; 06 February 2023 at 16:19. |
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07 February 2023, 14:12 | #7 |
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Thanks SpeedGeek. I was not even aware that existed.
I have been warned by several people to stay clear of anything above 120ns so that has become my truth |
07 February 2023, 14:27 | #8 |
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The A4000 doesn't allow you to set timings below 160ns either. :-)
Based on my experience, there will always be some unburnable EPROMs when buying these 27c400 chips from China. Also I have noticed when buying a bigger batch, that the dies behind the quartz window come in various shapes and sizes, yet they all have identical AMD printing on the package. "Curious." :-) |
07 February 2023, 15:26 | #9 |
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@ Jope: yeah I noticed that too. Those "China" versions are also suspiciously cheap... I bought a couple from European vendors. First of all, those are never "new" and never "cheap" but the Chinese versions (almost always knock-offs) often are (with date-marks saying 1997 etc....).
Personally I steer clear of China. They reverse-engineer, steal, copy, rob and rip like there is no tomorrow. I trust them as far as I can throw them... |
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