Extra ROM space via Zorro bus?

[zero]

The A3000/4000 can't take 1MB ROMs without a fairly drastic hardware mod. I'm wondering if extra ROM space could be added with a Zorro card.

On Zorro II a card could just map itself into the upper ROM space AIUI, but with the introduction of Zorro III that is no longer possible. Therefore I guess the card would have to auto-config and from there could load libraries and other resources that won't fit into the 512k ROM.

Unfortunately the Z3 bus is rather complex and scanning the reference "BIGRAM" example it would need at last one programmable device (maybe an FPGA) for interfacing.

Just an idea I'm throwing out... I can't think of any other way to get larger ROMs without any modding.

[NorthWay]

Didn't I read somewhere that ZII could map itself to $F00000(?)? (Yes, I thought that was odd - if not f00000 then some other address I'd never seen mentioned as proper ZII range.)

[Daedalus]

In theory, a Zorro-II board can map itself to anywhere in 24-bit space, but doing that is outside the Autoconfig process and so you have to be careful to get it to work as you still need to do the 68K handshaking. But it should be possible.

Zorro-III is a different story however since you're no longer just dealing with the 68K bus, but with a separate bus that emulates Zorro-II behaviour. I don't know for sure if all 24-bit accesses are passed through by Buster as Zorro-II accesses, or if it's just those within the Zorro-II memory space... Something for me to look at the next time I have some time.

[SpeedGeek]

I assume your "Drastic" hardware mod comment refers to A3K Romy since the A4K Romy is about as "Simple" as it gets. For A3K Romy, I looked at PLCC plug extensions to the Fat Gary socket. Unfortunately, they were quite expensive and have min. order requirements. Another problem was the extra height would cause problems for full size accelerator cards. So the desolder PLCC socket and resolder Romy solution was the most practical one.

Zorro bus solutions will be more expensive and VERY slow compared to mobo ROM access speeds... but Good luck anyway.

BTW, the $F00000 space is in fact part of the Zorro II space. But it was intended for Diag ROM Boards NOT Extended ROM Boards. So trying to use it in any other way creates 2 compatibility problems:

1) exec early startup code automatically jumps to any $F00000 Diag ROM
2) 3rd party 060 accelerator cards hijack the $F00000 space for 060 support code

[zero]

Zorro III should be decently fast, and you can always copy the libraries to FastMEM if you want speed.

Unfortunately the spec for Z3 says that addresses outside the Z3 address space are not available on the bus, unlike Z2 where you could indeed just overlay any part of the space or spy on custom chip access a la Action Replay.

SpeedGeek, you are right about the Romy for A4000, my mistake.

[gulliver]

@SpeedGeek

I would like to hear your technical opinion on Indivual Computers Kickflash 1MB Zorro II card.

http://wiki.icomp.de/wiki/Kickflash

Doesn't it solve the issue the OP presented? Or is it suboptimal?

TIA

[SpeedGeek]

@gulliver

An 8-bit card on an A2000 Zorro II bus = 1.75 MB/sec*.
... and for A3000/4000 Slow Buster = 1.2 MB/sec*.

Compared to Romy:

http://eab.abime.net/showthread.php?...mb+romy&page=3

Suboptimal is an understatement.

*Assuming zero wait states.

[gulliver]

@Speedgeek

Ouch, definately slow, and even slower under Zorro III slow buster.

Romy is certainly a lot faster.

And what about Elbox eFlash 4000?
http://www.elbox.com/products/eflash_4000.html

[NorthWay]

Originally Posted by gulliver

And what about Elbox eFlash 4000?

I believe both that and the KickFlash are basically storage devices that copy modules to memory.


I still want an in-circuit programmable 1M+ A4000D ROM flash solution. Something resistant to overwrites and with fixed address so you can protect and remap to fastram.

[zero]

Originally Posted by gulliver

@SpeedGeek

I would like to hear your technical opinion on Indivual Computers Kickflash 1MB Zorro II card.

http://wiki.icomp.de/wiki/Kickflash

Doesn't it solve the issue the OP presented? Or is it suboptimal?

TIA

Very interesting, thanks.

I guess it must use Autoconfig to run some code that soft-kicks the ROM in flash memory, similar to something like Relokick except that no RAM is needed and it happens during the early boot sequence.

Unfortunately I can't find an example basic Z2 card schematic to see what is involved. Reading the docs it doesn't look too complicated at all; I'm just wondering if I can throw something together.

[zero]

Originally Posted by NorthWay

I believe both that and the KickFlash are basically storage devices that copy modules to memory.

It says that it doesn't use any RAM.