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I would like to buy an EPROM programmer and some EPROM chips suitable for use as replacement BASIC ROMs for the Dragon 32 and 64. Can anyone tell me which EPROM chips I need, and where I could buy them along with a suitable EPROM programmer.

The Dragon 64 uses two 16k PROMs. These PROMs are compatible with the 27128 family of EPROMS. You can get these EPROMS from Maplin (http://www.maplin.co.uk) or ELFA (http://www.elfa.se) or similar. Some vendors don't seem to carry the 27128 anymore, but a pair of 27256 (32k) EPROMS can also be used. Just remember that the most significant address bit will be a "1" when using a 27256 so it is the upper half of the address space in these 32k EPROMs that will be used. Prices is in the EUR 3-6 range per EPROM.

It's been a while since I was looking for EPROM programmers. Batronix (http://www.progshop.com) seems to carry a good range where the least expensive programmers will be a good choice. These programmers start at about EUR 100. You'll probably want an eraser as well.

I don't have a D32 lying around anymore and my D32 schematic is close to unreadable, so I can't help you with finding suitable EPROMs there.

Hope this helps.
-- Rolf

Thank you very much for all your help!

rolfmichelsen wrote:I don't have a D32 lying around anymore and my D32 schematic is close to unreadable, so I can't help you with finding suitable EPROMs there.

I have plenty of D32's lying around. What information do you require in order to help finding suitable EPROMs?

Are any of the circuit diagrams at http://www.dragondata.co.uk/ readable enough?

I've given the schematics a try, but it is really hard to read the part numbers and pin numbers. However, it looks like the D32 contains two PROMs both with 13 address lines. That means two 8k PROMS, giving a total of 16k. Given my problem with reading all the pin numbers, I can't be completely sure but the 2764 EPROM is probably a good replacement. The memory world was pretty simple back in the 80's. If it has 8k capacity, it's compatible with the 2764

Rolf,
do any of the photographs in this thread viewtopic.php?f=5&t=110 help?

No, unfortunately they are of no help. All pictures with good enough resolution shows ROMs marked with "Dragon Data" and no part numbers. I'll take another shot at decoding the diagrams tomorrow...

I have photos of the innards of my D32, and I will re-upload them if you wish. Now I assume we are talking about IC17 and IC18, on my Dragon (Issue 2 board with OKI RAM) they are labelled as:

IC17
9364C-0032
47213
GI 8302 CSA


IC18
9364C-0031
47211
GI 8302 CSA

I have checked the diagrams and photos again, and it looks like I was terribly wrong regarding the D32 PROMs. These PROMs are 8k large but come in a 24 pin package. I am unable to find an EPROM that meets those specs. It is probably still pretty easy to replace the D32 PROMs with standard EPROMs by removing the PROMs from the motherboard and creating a custom board holding the replacement EPROMs and connecting it to the expansion port. This will require a bit more work, but quite doable even for a hobbyist using parts from Maplin or similar. Since I don't have a D32 myself anymore, I can't test this myself but I'd be happy to discuss with anyone interested in giving this a try.

I also checked the D64 diagrams again, and I am still confident that the D64 PROMs are compatible with 27128 EPROMs.

Thank you!

What chips were used for the Dragon 32 prototype? Could these be D32 compatible EPROM chips?
http://dragondata.worldofdragon.org/tec ... rd-top.jpg

I'm sorry that I cannot help here. The schematics and the address ranges in the pictures indicate that this is two 8k PROMs in a 24 pin package. I am unable to find any EPROMs that are compatible with those specs. AllDatasheet (http://www.alldatasheet.com/) is a good place to start if you want to dig for specs for old chips. The smallest EPROM I am able to find in current component catalogs is the 2764 (8k in 28 pin package).