Amiga 500 rev5 kickstart hack

[Tony Gunk]

Hey guys, long time no see

I was wondering if anyone could point me in the direction of a step-by-step guide on performing the hack that will allow you to connect newer kickstarts to a rev5 board (the one where you connect pin 1 to pin 31). I have an adapter, but I want to add a cpu upgrade and the adapter won't allow it to fit in the machine so I figure the old school way would work fine.

I have a soldering iron and all that but I don't have the necessary wire for performing it, I was also wondering where I could get this.

Thanks.

[zipper]

Perhaps: The below is valid for A2000 model A (rev < 4.1) and A500 rev 3 and rev 5 if the original instructions doesn't do it.
There should be no jumper between pin 1 and 31. Bend up pin 31 so that it doesn't have any contact with the socket.
Jumper pin 1 to socket 31. Make sure there's no connection to pin 31.
Solder a wire from pin 31 to 21. (from http://www.l8r.net/)

[Jope]

The old jumper 1-31 hack was only for 16bit mask ROMs as we had with 2.04 and 2.05. Those were always in 16 bit mode, so it was enough to just route the address line correctly with that jumper.

If you have an EPROM based kickstart, then you must do it as per Zipper's instructions, so that the EPROM is in 16 bit mode. The 21-31 wire sets the data width pin to the correct state.

[eXeler0]

Originally Posted by Tony Gunk

Hey guys, long time no see

I was wondering if anyone could point me in the direction of a step-by-step guide on performing the hack that will allow you to connect newer kickstarts to a rev5 board (the one where you connect pin 1 to pin 31). I have an adapter, but I want to add a cpu upgrade and the adapter won't allow it to fit in the machine so I figure the old school way would work fine.

I have a soldering iron and all that but I don't have the necessary wire for performing it, I was also wondering where I could get this.

Thanks.

I did a simple ”hack” to use 2.05 ROM

http://<br /> https://www.exretro.co...4.28.jpg<br />

This blog might also be of interest

https://retrozonesite.wordpress.com/...start-upgrade/

[Tony Gunk]

Originally Posted by zipper

Perhaps: The below is valid for A2000 model A (rev < 4.1) and A500 rev 3 and rev 5 if the original instructions doesn't do it.
There should be no jumper between pin 1 and 31. Bend up pin 31 so that it doesn't have any contact with the socket.
Jumper pin 1 to socket 31. Make sure there's no connection to pin 31.
Solder a wire from pin 31 to 21. (from http://www.l8r.net/)

Thanks for the reply,

The link you sent sends me to some "export services" website that seems to be totally unrelated :v Is there any other similar resource, preferably with some kind of diagram? I am still pretty new to this kind of thing so I wouldn't want to accidentally ruin my machine by doing something wrong.

Also, my kickstart is an EPROM with 3.1 on it, the kickstart splash screen just says "3.x"

[Jope]

Originally Posted by Tony Gunk

The link you sent sends me to some "export services" website that seems to be totally unrelated :v

It is quite Amiga related, but very old.

The relevant page (accessible via a series clicks from the front page) is here:
http://www.l8r.net/technical/t-204rom.shtml

Also, my kickstart is an EPROM with 3.1 on it, the kickstart splash screen just says "3.x"

Yes, so you need to do the 1-31 swap on the socket and the 21-31 jumper on the eprom.

[Tony Gunk]

Originally Posted by Jope

It is quite Amiga related, but very old.

The relevant page (accessible via a series clicks from the front page) is here:
http://www.l8r.net/technical/t-204rom.shtml



Yes, so you need to do the 1-31 swap on the socket and the 21-31 jumper on the eprom.

Ah okay, the front page doesn't indicate much so I was a bit confused.

So to clarify, I can connect pin 1 to 31 of the socket on the backside of the board, and for pin 21 to 31 on the EPROM, but for that does pin 21 need to be bent upwards also or no?

Also, is there a diagram of the socket and the EPROM available so I can make sure which pins are which?

[Jope]

Yep, do it like that. Only pin 31 needs to be bent upwards. Pin 21 needs to go to the socket to for your voltage feed to the chip, and via the jumper, as the pull up for the _BYTE signal.

Googling for 27c400 pinout provided me with this: http://www.boobip.com/application/fi...400_pinout.png

[Tony Gunk]

Originally Posted by Jope

Yep, do it like that. Only pin 31 needs to be bent upwards. Pin 21 needs to go to the socket to for your voltage feed to the chip, and via the jumper, as the pull up for the _BYTE signal.

Googling for 27c400 pinout provided me with this: http://www.boobip.com/application/fi...400_pinout.png

For the EPROM, are the pins in the same place as the diagram you provided, or is this just the pin out for the socket?

[Jope]

This is the pinout for the EPROM. The pinout for the socket can be found in older A500 schematics.

Data, Address and control buses:
https://archive.org/details/Commodor.../n235/mode/2up

Power feed:
https://archive.org/details/Commodor.../n245/mode/2up

Part U6 (type HN62402) is the ROM socket.

[Tony Gunk]

Okay, I'll get what I need and try it out and I'll reply here again and let you know if it was a success.

[Tony Gunk]

Originally Posted by Jope

This is the pinout for the EPROM. The pinout for the socket can be found in older A500 schematics.

Data, Address and control buses:
https://archive.org/details/Commodor.../n235/mode/2up

Power feed:
https://archive.org/details/Commodor.../n245/mode/2up

Part U6 (type HN62402) is the ROM socket.

So I'm getting ready to perform the patch and I was wondering what kind of wire should I use to connect the pins? I desoldered the connection cable from a non working A500 keyboard, would that work or do I need something specific?

[Jope]

That's fine. It isn't very picky about the type of wire you use.

[Tony Gunk]

Originally Posted by Jope

That's fine. It isn't very picky about the type of wire you use.

Alright thanks, I'll reply again later to update if it all went well.

[Tony Gunk]

UPDATE: I was able to get it working, my soldering job is kinda messy looking but I'm still pretty new to it, but it works so that's all that matters.