Thank you for the great explanations. Short and concise without fluff.

I would love to do this to my A500! This tutorial is much appreciated!

Awesome work!! Thanks for sharing

Excellent video, thanks for sharing this knowledge. Greetings from Argentina

Thank you for taking the time to make this video. I've got my chip in the UV oven as I type! Going to route my switch into the gotek oled display enclosure

@retrofriends

2 жыл бұрын

Good idea!

@justinthomas2458

2 жыл бұрын

Well the two 27c800 chips I have both failed to write "Write failed, Address=0x002000, Buffer=0x6E Device=0x00" I tried writing some (5 total) 27c400 chips with kick 1.3 only and they all fail at the same point. I have J5 jumper closest to the ziff socket and J1 at the topmost pins. All chips have been ran through my UV eraser and blank checked. I'm using legit roms just purchased through amiga forever. I've also tried the 4x4 with and without external power. All attempts result in the same write failed message. Could it be that all 7 chips are bad with the same error or what am I missing!?

@retrofriends

2 жыл бұрын

@@justinthomas2458 Not sure I can provide more help than the video. I review potential issues one might experience, but I can't account for them all. Sorry I can't be of more help.

Totally awesome! Thanks for the video.

@retrofriends

3 жыл бұрын

You are welcome :)

VERY well documented and laid out! Had to Subscribe on this Video alone! Keep up the great work. -Mark.

Wonderful and instructive video. Many thanks 👍

Nice! I like not needing a socket into a socket as the solution but then of course you can't hide the resistor underneath, which looks tidier

Nice. I wonder if you could use a 74ls74 flip flop clocked by the reset pulse to capture some key press signal during the reset and remove the need for the switch.

@retrofriends

3 жыл бұрын

The one-chip solution is what I was looking for. Alternatively, there are many options for the active-low. I know you can make a circuit for holding CTRL+A+A for several seconds to switch.

Very nice!!

This is a great tutorial on how to build a rom switcher. Can you tell me how you build build the circuit for making it switch by the Ctrl+A+A as i would like to have one with no switch at all

@retrofriends

3 жыл бұрын

No I can't really tell you here. Some people have done it I believe, but you will have to search elsewhere.

If I O ly need one rom which epprom need for a ks1.3 and wich one for the 3.1

Would be nice to know the following : could you burn rom 1.2, 1.3, and 3.1 (size wise that should be possible) -- but how would you go about selecting the 2nd 256k image ? Also, similarly, using 27c160, and 27c322 eproms for 2MB or 4MB eproms, (for 27c800, you could have 2x512kb roms, or up to 4x256kb roms, but for 27c160, one should be able to have 8x256kb roms, or 4x512kb roms or a combination there of, finally the 27c322 roms should hold 16x256kb roms, or 8x512kb roms ) -- do you know how one would select between up to 16 rom images ? -- i am guessing a pcb to control this might be in order).

@retrofriends

2 ай бұрын

If you make a rom switcher that lets you pick between 16 roms using these chips, I would post it up somewhere because that would be unique. This is a simple ROM switcher using one wire to select one half of the chip or the other. Anything else would be way more complicated and beyond the scope of what I had hoped to achieve with this video.

Are you using the 256 kb rom twice purely for convenience? Like could you replace the second with an empty rom full of 0's if you wanted? Or does it need to be the same data twice for some weird reason?

@retrofriends

2 жыл бұрын

Seems riding the data twice as a commonly accepted way of doing it. Theoretically I would think you could fill it with zeros, but it's so easy to copy the data I've never bothered to try.

What is the access speed for the 800 ROM you use for this venture? Also, I note that you renamed your files during the concatenation command line from those that you downloaded. Figured out what you were demonstrating though 👍 Re the programmer, I know some older legacy programmers would need voltages higher than 5v to do programming on older style EPROMs such as these, sometimes above 12 or 18v I believe. So using an external PSU for the programmer is probably good practice rather than relying solely on the USB port for supply voltage. 😎

@retrofriends

3 жыл бұрын

120ns EPROM. You missed when I renamed the ROMs during the byte-swap procedure, maybe? You can't skip that step :) I do only refer to the programmer featured, but I mention external power may be needed in some cases.

This mod seems to work on an A600. Does is work on an A500 rev5 board?

@craftsman123456

3 жыл бұрын

Sorry I see the opps bug.

can you post a new link for programmer and adaptor?

@retrofriends

3 жыл бұрын

I tested the Amazon link, and it still works. Not sure why you are having difficulty.

Can it put 1.3 & 3.4.1 on one rom?

@retrofriends

3 жыл бұрын

You must mean 3.1.4, and yes as long as the image is 512k it should work.