PDA

View Full Version : Burn a new ROM for my Kaypro...



geneb
February 7th, 2012, 02:21 PM
I've got a Kaypro 4/84 that arrived today (rescue) and I'd like to install the KayPLUS ROM in it.

The KayPLUS ROM is designed to fit into a 2764 EPROM (the image is 8k). My problem is that the only parts I have laying around are 27256s.

Is there any reason I can't create a "quad" sized image (essentially create a new image file by binary copying the 8k files into a single 32k file) and then install this in the Kaypro? I've done something similar in the past on my C-64, but I added a switch & resistor to bounce between two ROM "images" on the same part.

Barring that, does anyone have some 2764s they want to sell cheap? :)

tnx!

(fyi, the KayPLUS ROM & docs can be downloaded here: http://www.microcodeconsulting.com/z80/kayplus.htm )

g.

gubbish
February 7th, 2012, 02:33 PM
Just peeked at the data sheets, and it looks like since the only difference between the two pinouts is the A13 and A14 pins. So I think you could just replicate the 8k ROM image 4 times to fill the 32k 27256, and it should work without any modification. Curious to hear how this works out, I have a Kaypro that I was thinking of doing this with. Good luck!

carlsson
February 7th, 2012, 03:34 PM
Boring answer, but it seems you can get 2764 chips off eBay for $3-4 each including postage. The only way to find a cheaper one is if someone is kind enough to donate a chip or two.

MikeS
February 7th, 2012, 04:02 PM
No problem, Gene; either duplicate the image as Gubbish suggests or do the same thing as your C64, bend out pins 26 and 27 (or slip a socket in between) and either connect some jumpers or even a 2-position DIP switch to select among up to four versions.

But if you really want some 2764s I've got a few that I can spare; didn't I send you some Z80 chips way back when?

geneb
February 7th, 2012, 04:45 PM
Ok, ROM burned successfully. :) Kaypro comes up and begs for a disk. Now I need to transfer the KayPlus utilities to a disk in order to create bootable media for the new ROM.

If I get a chance, I'll create an Image Disk copy of the new media to make it easier on folks if they want to try this themselves.

Anders, you're correct about the 2764's on eBay, but by the time they arrive I'll be otherwise occupied and won't get back to the Kaypro for a couple of months. :)

g.

geneb
February 7th, 2012, 04:47 PM
No problem, Gene; either duplicate the image as Gubbish suggests or do the same thing as your C64, bend out pins 26 and 27 (or slip a socket in between) and either connect some jumpers or even a 2-position DIP switch to select among up to four versions.

But if you really want some 2764s I've got a few that I can spare; didn't I send you some Z80 chips way back when?

Yeah, I think you did. :) When I get more time I think I'll make a dual boot ROM to hop between just two images - a toggle switch and a 470ohm (?) resistor is all that's needed to pull that off.

The board actually takes the 27C256 I fed it and worked great - I just need to build boot media for the new ROM.

tnx!

g.