Open source 14MHz 68000 accelerator

[nikosidis]

Originally Posted by Mathesar

What prices have you found? You can use almost all 32TSOP-II 512K * 8 SRAM chips.
This is a selection on digikey:
https://www.digikey.nl/products/en/i...=1&pageSize=25

Thanks Mathesar

Did not know that.
So from the link you provided it is possible to use the cheapest one?
Two of those is only 6 Euro + shipping so that would not be bad.

[Mathesar]

Yes, you can use the cheapest one. Only problem is: digikey = minimum order cost
May I recommend aisler.net? With that pcb service you can also order components from digikey, mouser, farnell, etc. You pay a bit more then but you do not have to make the minimum order cost.
Worth a look!

[nikosidis]

Originally Posted by Mathesar

Yes, you can use the cheapest one. Only problem is: digikey = minimum order cost
May I recommend aisler.net? With that pcb service you can also order components from digikey, mouser, farnell, etc. You pay a bit more then but you do not have to make the minimum order cost.
Worth a look!

Thanks Mathesar

I will have a look into it

[keithamiga1200]

Originally Posted by nikosidis

I'm planing to build some but the sram is quite expensive.

I've been looking in to this myself. Are you definitely going to get these sourced for group buy? No point in duplication

[keithamiga1200]

Originally Posted by Mathesar

Yes, you can use the cheapest one. Only problem is: digikey = minimum order cost
May I recommend aisler.net? With that pcb service you can also order components from digikey, mouser, farnell, etc. You pay a bit more then but you do not have to make the minimum order cost.
Worth a look!

A group buy on components, would reduce costs

[nikosidis]

Originally Posted by keithamiga1200

A group buy on components, would reduce costs

The components are one thing but there is work involved. That is the most expensive part.

If we can buy 100 pcs and save 10% it will not make the card a lot cheaper.

The design is great but looking at alternatives it would be hard to sell something like this for over 70 Euro + shipping inkl. CPU.

[keithamiga1200]

Originally Posted by nikosidis

to sell something like this for over 70 Euro + shipping inkl. CPU.

Yikes that's expensive.

[Mathesar]

I think the fun in this board is that it can be build as a DIY project. You don't need a programmer or other specialized tools; A soldering iron, solder, flux, a tweezer and some form of magnification (or young eyes!) is all that is needed.
Take a look here where I've partly configured the V2.2 board for ordering with components (only need to add in the logic IC's).
If you order 3 boards with the cheapest lead time, you pay 31 euros per board inc shipping with all parts except for the logic and the CPU (but with RAM, sockets, passives, etc included).
V2.2 at Aisler.net
Of course, you will have to solder yourself.

PS group buys have become a bit more expensive with all the new european postage rules. Where I used to send PCB and small parts all over the world with just post stamp I now need to send "goods" as parcels instead. This needs to be added into the cost when you do group buys and then have to split and send the parts all over the world.

PS2: Would a THT (through hole components) version be easier to build?

[amigoun]

THT would definitely bring it more retro feeling, so it would be nice to have this variant.

[patrik]

@Mathesar: Great work! Somewhat intrigued that it is possible to build such an elegant thing without programmable logic.

[Mathesar]

Originally Posted by nikosidis

Thanks Mathesar

Did not know that.
So from the link you provided it is possible to use the cheapest one?
Two of those is only 6 Euro + shipping so that would not be bad.

OOPS forgot what I said, the cheapest one in the link is not a 5v part...

[nikosidis]

Originally Posted by Mathesar

OOPS forgot what I said, the cheapest one in the link is not a 5v part...

Ok, thanks

[keithamiga1200]

Originally Posted by Mathesar

PS2: Would a THT (through hole components) version be easier to build?

Actually, the sop ICs are pretty easy to solder (nice width between pins), it's the 0805s that p** me off They're do'able, but their not fun to solder.

[Mathesar]

Originally Posted by keithamiga1200

Actually, the sop ICs are pretty easy to solder (nice width between pins), it's the 0805s that p** me off They're do'able, but their not fun to solder.

I'll do a THT version :-)

[katarakt]

Originally Posted by Mathesar

Variants

The accelerator can be build in 3 variant:

• Accelerator only This only doubles the clock of the CPU to 14MHz.
• Accelerator plus 1MB zero waitstate ranger RAM The above but adds 1MB of fast RAM. This makes the accelerator about 2.7 times faster than a stock A500
• Accelerator plus 1MB zero waitstate ranger RAM plus disable circuit The above but adds a timer based disable option for the RAM. By holdiing ctrl-amiga-amiga down for more than 5..6 seconds the RAM is disabled.
  It is enabled again on the next (less than 5..6 seconds) reset cycle

Mathesaer,what is it exactly ....we have 3 different ram (chip,fast, slow)...and slow ram is also known as ranger ram

[Mathesar]

Originally Posted by katarakt

Mathesaer,what is it exactly ....we have 3 different ram (chip,fast, slow)...and slow ram is also known as ranger ram

The ram on this accelerator is actually fast ram. However, I mapped it to the address range of the slow/ranger ram @$C00000 so it gets autodetected without doing the whole zorro/autoconfig stuff. (I had to keep things simple as I only used standard logic.)

Any real slow ram installed in the trapdoor gets overruled. When the accelerator ram is disabled then the trapdoor slow ram appears again.

[GadgetUK]

Does anyone know how you can force the caching of Kickstart into the slow RAM at C00000 rather than it putting it in Fast RAM provided by an A590?

I have this card working fine, but as soon as you add fast RAM to the system, that has a higher priority and ends up (ironically) slowing the system down to 7Mhz because the ROM is cached in fast RAM vs where it needs to be in the ranger / slow @ C00000

EDIT: Will try ChangeMemPri - see if that helps!

[GadgetUK]

Well, not sure what's going on - it seems when there's no additional fast RAM - all is OK, runs at 14Mhz. As soon as you add fast RAM, that gets a higher priority and thus everything runs at 7Mhz. ChangeMemPri does change the priority, but the system then crashes. Any ideas? Has anyone else got one working with additional fast RAM?

[Mathesar]

Have you build this card and is it working?
I have not received any feedback of people having succesfully build one.

[GadgetUK]

Originally Posted by Mathesar

Have you build this card and is it working?
I have not received any feedback of people having succesfully build one.

Yes - built all OK =D sparxUK built a few and sent me parts to build one, which was very kind of him =D


All works OK - was just trying to use the A590 to add SCSI and a bit of RAM.
I tried disabling the fast RAM on the A590 and it fails to boot at all. So I suspect the issue there is an incompatibility with the A590 - since it should fall back to PIO mode.