EPROM 27C800 with Amiga 1200 kickstart

[mjnman]

Hi,
i need to create a kickstart roms for amiga 1200. I saw a lot of people used two 27C400. My question is...can i use two 27C800 with pin 1 cut (A18) and connected with pin 22 (VCC)?
The link below wrote about switcher with 27C800:
https://www.tsb.space/knowledge-base...-27c800-eprom/
thanks

[alexh]

You can use two 27C800 EPROMs if you wanted to. No modifications needed for a single 2MB ROM. The A1200 already has 42-pin EPROM sockets and hardware to control A18.

If you want to manually select between two 1MB ROMs. Bend pin 1 (A18) on both EEPROMs and connect to a switch (selecting between VCC & VSS).

[levo-ace]

If you just want the one image then connect A18 to GROUND to select the lower bank , connectimg it to VCC will select the upper bank.

[alexh]

Originally Posted by levo-ace

If you just want the one image then connect A18 to GROUND to select the lower bank.

The A1200 motherboard already handles A18 no need to connect to anything for just one ROM. Just plug in your EPROMS.

[mjnman]

@alexh
can I therefore burn a entire kickstart rom in a single 27C800 and put in U6A (HI) or U6B (LO)?

[alexh]

Originally Posted by mjnman

@alexh
can I therefore burn a entire kickstart rom in a single 27C800 and put in U6A (HI) or U6B (LO)?

Yes.

Some care has to be taken when using Romsplit/Remus to create a working 2MB ROM image but it is intuitive enough. And there are lots of guides.

If you just want burn a pre-existing "standard" 0.5MB ROM image (e.g. KS3.1) then I am sure that will work just fine too. The main issue when using 2x16-bit ROMs is splitting the file correctly (if it is not already split). Again, use google to find a guide.

Your EPROM programmer software might also complain the split files are smaller than the ROM parts, in which case you might have to pad the files.

[mjnman]

ah ok...with two 27C400 rom i need to split and swap BYTE but with single 27C800 eprom is it only a single program?

[alexh]

Originally Posted by mjnman

ah ok...with two 27C400 rom i need to split and swap BYTE but with single 27C800 eprom is it only a sinlge program?

You can't use a single 27C800 EPROM in A1200. You have to use two just like 27C400. And you have to go through the same process of splitting.

[mjnman]

thanks, now it's clear