Amiga hardware info, help and support with a focus (but not limited to) North American NTSC experiences. Open to all.
User avatar
A10001986

by A10001986 posted Tue Jan 22, 2019 12:28 pm

A10001986 wrote:It is pointless to even try to use this in a big box such as the A2000. The auto config logic would be completely messed up. You wouldn't be able to run any zorro 2 auto-config boards any more, and thereby in essence reduce your a2000 into an a500.


Do. Not. Use. That. 8MB. CPU-socket. Board. In. A. Big. Box. Amiga.
User avatar
McTrinsic

by McTrinsic posted Tue Jan 22, 2019 2:31 pm

Well to be honest I do not fully understand why you are so keen on this 8mb board.

The advantage of the big box amigas such as the a2k is the expandability. You might as well get a board such as the ZorRAM or BigRAM.

I’d consider an accelerator with FastRAM.
User avatar
jdryyz

by jdryyz posted Tue Jan 22, 2019 3:03 pm

Mainly due to cost. Can't beat the price for 8MB. At the time time of this writing, I cannot even locate a source for a measly 2MB to fill the A2091. I saw a 2MB kit on eBay a while back for $59 plus shipping but thought I could do better. It may already be sold anyway.

Also, other Zorro II autoconfig boards can live together in an A2k. What makes this 8MB expansion different (aside from its placement in the 68000 socket)? Is it using some unorthodox methods? The seller does say there are different ways it can be programmed, presumably to increase compatibility.
User avatar
jdryyz

by jdryyz posted Tue Jan 22, 2019 3:23 pm

I'm curious on the other boards you mention. I could not find much about ZorRAM but I did find BigRAMPlus here.

That is a Zorro III board though.

Are both of these readily available?

Thanks.
User avatar
rpiguy9907

by rpiguy9907 posted Tue Jan 22, 2019 8:30 pm

Yes many autoconfig boards can work together on an A2000, but this 8mb is not autoconfig. Yes the Amiga will automatically recognize the memory, but that’s not the auto config people are referring to - it is a specific feature of the Zorro bus and this expansion will nerf that feature. It is possible that your 2091 would no longer work.

Just buy this.

Deal won’t last long...
User avatar
McTrinsic

by McTrinsic posted Tue Jan 22, 2019 10:15 pm

I apologize, you’re right - ZorRAM and BigRAM (+) are Zorro 3 only and not for the A2000.

The other readily available alternative would be to get an CPU-Slot-Adapter from Amibay and use an ACA500+ in it. Since with this you can also use CF-Cards it might help you with the mass storage topic.
User avatar
jdryyz

by jdryyz posted Tue Jan 22, 2019 10:16 pm

I saw that board earlier this week. Not too shabby. A shame it is not fully populated for that price. Another 32 chips would be needed to fill it and I wonder if they too are just as scarce/costly.

So I take it there isn't enough "logic" included in the 8MB expansion for true autoconfig? Too bad. I will put that option aside for now.

My goal with my A2K revival is to bring it to a specific level of usability without throwing too much $$ at it. I have made a few inexpensive advances in that direction so far. I have no desire for an accelerator but 8MB of Fast RAM seemed to be within my grasp. If there are Zorro II possibilities in the ~$60 range, I will gladly explore them. That is probably unrealistic though.


rpiguy9907 wrote:Yes many autoconfig boards can work together on an A2000, but this 8mb is not autoconfig. Yes the Amiga will automatically recognize the memory, but that’s not the auto config people are referring to - it is a specific feature of the Zorro bus and this expansion will nerf that feature. It is possible that your 2091 would no longer work.

Just buy this

Deal won’t last long...
User avatar
A10001986

by A10001986 posted Wed Jan 23, 2019 6:42 am

The MKL board is, of course, an auto-config device. Reason for not being an ideal solution for the A2000 is ... well, the auto-config chain.

Auto-config devices need a config-in signal and provide a config-out signal. When config-in is triggered, the ac-device activates its configuration registers so the CPU can read from and write to them. When configuring the device is done, the CPU triggers a signal that tells the device to disable its registers. When device is done doing this, it activates its config-out pin. Then the next auto-config-device gets a config-in signal. Electrically, this is done by using a device's config-out as the config-in of the next device in the chain. Hence "chain".

Note that "config-in" or "config-out" are not bus signals, but separate physical electrical pins in slots and on connectors.

Big box Amigas have several slots. Each slot's config-out pin is hard-wired to the next slot's config-in pin. In other words: The slots form a chain. (And there some logic involved to skip empty slots, but that's irrelevant here and now).

The MKL devices (v58, v59 and what not) vary in providing either only config-in, only config-out or both as physical connector pins. However, those pins need to be electrically inserted into the auto-config chain. Just plugging it into the CPU socket does not do that.

For example: Some MKL versions lack a config-in pin and, instead, logically assume their config-in triggered upon booting, so that the card's config registers are automatically visible. Unfortunately, so does the first slot in the Amiga, resulting in two devices occupying the auto-config memory space at the same time. Needless to say, that does not work.

If the MKL board in question only has a config-out pin, this pin needs to be connected to the next device's config-in pin, ie it needs to be wired the corresponding slot's config-in pin. That's a problem because
a) as mentioned, he first slot in order has its config-in hardwired as "triggered" (iow: you'd need to cut a trace on the motherboard),
b) the MKL board's config out never reaches config-in of any slot (iow: the board's config out needs to be connected to the first slot's config-in).

The "first" slot in the A2000 is the coprocessor slot. Its config-in is pin 12, which is hardwired to GND (which means it's active). Pin 11 is config-out. (Only on the A2000B, not the original A2000A)

See also page 94 of the A500/A2000 reference manual (for example here)

PS: The same goes for A500s and A1000s with expansion cards connected to the 86pin side connector. Those connectors have a hardwired config-in pins for expansion cards. Therefore, connecting ac-devices with MKL-like boards sitting in the CPU socket requires a modification to the connector's config signals.
User avatar
jdryyz

by jdryyz posted Wed Jan 23, 2019 10:58 am

Thanks for all the info. I'm convinced that it is not a good choice for an A2000.

Who is online

Users browsing this forum: No registered users and 1 guest