A500 Rev 5 KS Adapter

[rfancella]

Hello all!
I built up a couple Kickstart adapter boards. I do not fully understand the jumpers and am looking for some enlightenment on the subject.
This is the one I built: https://www.pcbway.com/project/share...HERBOARDS.html


The build went well, but if I put a known good working 27C400 into it, no matter which jumper settings I use, it will not boot. I also burned a 27C800 with DiagROM and Kickstart. I tried every combination of jumpers and it will not boot either.


Thank you for any advice!
Ron

[Jope]

The jumpers won't do anything with a 27C400, as it doesn't have that many address lines.

Known good working means that the EPROM you're using works in a rev 6 machine?

I take it that your rev 5 still boots with a 1.2 or 1.3 mask ROM?

[rfancella]

Hi and thank you for the reply.
By known good working I mean it is a 27C400 with KS3.2.2 that works just fine on this rev 5 board.
I put the eprom in and it boots. I put the eprom in the adapter and the adapter on the board and get a black screen.
My primary question is more, what are the jumpers for with a 27C800 or 27C160? Which banks are selected with the jumpers on each chip? (JP1O - JP1 open...)

___________JP1O/JP2O JP1C/JP2O JP1O/JP2C JP1C/JP2C
27C400
27C800
27C160

Thank you,
Ron

[Jope]

The jumpers enable or disable A18 and A19. Basically this just gives you four extra banks that you can choose from depending on what you select. Of course your EPROM needs to be large enough to have A18 for the A18 jumper to do anything and in addition it needs to have A19 for the A19 jumper to do something. You can find EPROM pinouts via google, there you can check to see whether your particular part has A18 and A19.

It's just binary, the jumper settings are 00 01 10 11 for banks 0 1 2 3 respectively.

Now about your 27c400 chip. This chip will not work in a rev 5 board by just plugging it in as it is. You must bend some pins and solder a few wires to the chip. Are you trying the chip with the bend + wires in this adapter? If so, that will probably conflict, as the adapter does these modifications for you.

If your chip works without any bent pins and added wires, then you probably do not have a rev 5 motherboard?

[rfancella]

Thank you again for your reply!

As to the eprom working, you are 100% correct. I pulled the board and took a look at the back of it. I modded it years ago and sure enough, a couple bodge wires and a couple cut traces. MAN! My memory is going.
I'll revert the mod and test the adapter again.


Thank you,
Ron

[Nbdy]

I think that 27c400 should work without any adapter pins ...

The adapter pins are for 27c800 and 27c160 eproms ...

[rfancella]

Woohoo! Sorted!
Thanks Jope for your input. I figured out the jumpers and reversed the mod and the adapter works 100%. Figured while I was installing a switch for the Kickstart, I also ran some wires and installed a SPDT switch and now can change between KS1.3 or KS3.2.2 and 1mb Chip ram or 512k Chip and 512k Fast ram. Thank you all for your help!


Thanks,
Ron

Originally Posted by Jope

The jumpers enable or disable A18 and A19. Basically this just gives you four extra banks that you can choose from depending on what you select. Of course your EPROM needs to be large enough to have A18 for the A18 jumper to do anything and in addition it needs to have A19 for the A19 jumper to do something. You can find EPROM pinouts via google, there you can check to see whether your particular part has A18 and A19.

It's just binary, the jumper settings are 00 01 10 11 for banks 0 1 2 3 respectively.

Now about your 27c400 chip. This chip will not work in a rev 5 board by just plugging it in as it is. You must bend some pins and solder a few wires to the chip. Are you trying the chip with the bend + wires in this adapter? If so, that will probably conflict, as the adapter does these modifications for you.

If your chip works without any bent pins and added wires, then you probably do not have a rev 5 motherboard?

Originally Posted by Nbdy

I think that 27c400 should work without any adapter pins ...

The adapter pins are for 27c800 and 27c160 eproms ...