A2000 Zorro slot issues

[nikoskob]

Hi everyone,

Just a quick question, is the Buster chip responsible for what goes on with the Zorro slot in the A2000? As in, when you insert a card into a slot, does Buster allow the communication lines to open to the rest of the board?

Also, is Buster in anyway responsible for the cpu slot?

Cheers

[hooverphonique]

yes, buster takes care of communication between the zorro slots and the rest of the machine.

[Jope]

More precisely, the Buster in the A2000 handles bus arbitration for Zorro II cards. Basically it allows the cards to request and relinquish 68000 bus ownership for DMA transfers.

The communications lines are open all the time otherwise, most Zorro II cards do not wish to become bus masters.

Edit: and sure, the cpu slot bus mastering also goes via Buster in a B2000.

[nikoskob]

Originally Posted by hooverphonique

yes, buster takes care of communication between the zorro slots and the rest of the machine.

Originally Posted by Jope

More precisely, the Buster in the A2000 handles bus arbitration for Zorro II cards. Basically it allows the cards to request and relinquish 68000 bus ownership for DMA transfers.

The communications lines are open all the time otherwise, most Zorro II cards do not wish to become bus masters.

Edit: and sure, the cpu slot bus mastering also goes via Buster in a B2000.

Thanks guys, I had a feeling that may be the case, because if I don't have any boards plugged in, board boots without issues, I can get to the pre-boot screen as well, but as soon as I plug a card in, either I will just get a light grey screen, or just the white screen. If I try the pre-boot, doesn't work, or if it does, I get a guru error instead.

I'll look at the Buster chip to see if there is anything out of sorts.

Another question, is it common for Buster chips to fail?

Edit: Just pulled the buster off the board, and noticed that the socket is extremely dirty, almost looks like there is some corrosion, but I think its mainly dirty. I'll replace that and see if there is any difference with zorro cards.

[Jope]

It's not a common failure point in an A2000, but that doesn't mean it can't fail. :-)

[nikoskob]

Had a good look at the board over the weekend, went over all the traces again, zorro slots, cpu, kickrom, buster, all buzzed out fine, no broken traces or anything

Then I decided to use the logic probe and started checking the address and bus lines next to the cpu slot, and found that one of the 74ls245n chips (U605, PIN5), wasn't pulsing on a bus line like the rest of the pins.

I'm hoping that is the issue, but of course, I don't have any on hand, and no local shops have them in stock

I'll order some and once I replace it, fingers crossed, i'll have working zorro slots

Edit: Sorry, U604, not U605

[nikoskob]

Finally sorted!!

It was U605, plugged in a new 245N and zorro slots are up at running, only that i butchered the resistor network , but working non the less.

Thanks for the help everyone