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[Darrin]

OK, all Minimig v1.1 owners prepare to weep like children! Our resident genius Yaqube has just posted a demonstration of Hardfile support on the Minimig v1.1 with his ARM extentension board.

Follow this link to see his post and then click on his link to go to uTube and watch the 6 minute demonstration of his machine booting into what looks like Workbench 3.0/1, running Sysinfo and then playing several hard drive installed games:

http://www.minimig.net/viewtopic.php?f=7&t=11&p=153#p153

You might also note that this Minimig has the following:

68000 @ 25MHz (should help with those flight sims)
1.5MB Slow RAM
2.0MB Chip RAM
4 x Floppy drives (df0, df1, df2 and df3)
1 x 512MB Hardfile showing as a FFS SCSI drive

Brilliant work! This really is a complete expanded A500 replacement suitable for most people.

[whiteb]

Ummmm, my normal minimig only has 2MB on the board, I take it this one has new ram or something, or does the ARM contain RAM that configs as well ?

According to the Youtube comments, Ram was "Piggy Backed", you cannot just plop on two more chips and have them work surely ?

I thought you would at least need to separate them via Address lines ?

[Darrin]

whiteb wrote:
Ummmm, my normal minimig only has 2MB on the board, I take it this one has new ram or something, or does the ARM contain RAM that configs as well ?

According to the Youtube comments, Ram was "Piggy Backed", you cannot just plop on two more chips and have them work surely ?

I thought you would at least need to separate them via Address lines ?

I've no idea. I've posted the question and I'll be interested to see the answer. :-)

Edit: and here's how, plus a picture:

http://www.minimig.net/viewtopic.php?f=3&t=27

[rkauer]

To piggyback a RAM chip, just separating the most significant bit address will suffice.

[whiteb]

I see from the link Darrin supplied he is using the Extra I/O plug to (I think) route signals to the new chips no doubt a couple of address lines. That is Soldering FAR IN ADVANCE of my own.

[edit] actually, that could VERY WELL be it.

From memory, the 68882 occupied *A LOT* of the same signals that the 68xxx occupied, You just had to select the specific address lines that the chip used. I do not know the pin outs of the chip, it looks like one pin may be bent up, and wire'd, maybe a "CS" (Chip Select) line, with the rest coexisting signals that both chips use ?

[edit2] Yeah, if that is indeed pin 6 in the picture, that is CE (Chip, Enable input). You just disable that pin on the FPGA, the Existing chips will NEVER receive CE, and it will ignore EVERYTHING ELSE (or how i understand it).

[Darrin]

My soldering skills are zero too, but I'm sure I can pay someone local to do it when the exact instructions are published.

[TheDaddy]

Great stuff Jakub! :-)

[weirdami]

if that ram chip piggy backing thing works then why aren't manufacturers doing it to save on sockets and stuff?

[Darrin]

weirdami wrote:
if that ram chip piggy backing thing works then why aren't manufacturers doing it to save on sockets and stuff?

Probably because your average PC motherboard has plenty of room for extra sockets and your average PC user doesn't want to piddle around with a soldering iron when he upgrades his RAM. :-)

[whiteb]

weirdami wrote:
if that ram chip piggy backing thing works then why aren't manufacturers doing it to save on sockets and stuff?

Sockets are used for ease of putting in/Taking out.

This trick is done, to *DISABLE* the existing chip, in favor of the new chip. Also, given the nature of the board, its *FRAGILE !!!!!*. I have tried to desolder a damaged minimig, and lifted the pads in the process (hey, it was damaged), so you just solder over the top of the existing one, and just re-route the 'Chip Select' line.

This way it is ONE or the other, not both. If it was to use BOTH ram, then you would need independent addressing (At least).

[Darrin]

whiteb wrote:
This trick is done, to *DISABLE* the existing chip, in favor of the new chip. Also, given the nature of the board, its *FRAGILE !!!!!*. I have tried to desolder a damaged minimig, and lifted the pads in the process (hey, it was damaged), so you just solder over the top of the existing one, and just re-route the 'Chip Select' line.

This way it is ONE or the other, not both. If it was to use BOTH ram, then you would need independent addressing (At least).

Ah so this was a "safer" way to replace the existing RAM chips without having to remove them?

[Illuwatar]

Clever idea by yaqube with the piggy backing. But he is not disabling the original 2 MB SRAM on the board - he adds an extra 2 MB (making up these 4 MB total). The CS1-pin (nr 6) are used to choose what half of the 2 MB that will be used. All other pins are connected in parallel - that is normal and should be like that. Even on a standard 2 MB MiniMig, all pins except of CS1 are connected in parallel. The core of the FPGA has been modified to provide four chip select signals instead of just two.

Someone complained about the amount of free space at my MiniMig design - here is a reason to fill it up... these mods will keep me busy changing the design all the time. I hope there will be a final so I can make the Ultimate Mini-ITX MiniMig. I would be nice to put that ARM thing right on the motherboard too...

[mongo]

whiteb wrote:

This trick is done, to *DISABLE* the existing chip, in favor of the new chip. Also, given the nature of the board, its *FRAGILE !!!!!*. I have tried to desolder a damaged minimig, and lifted the pads in the process (hey, it was damaged), so you just solder over the top of the existing one, and just re-route the 'Chip Select' line.

This way it is ONE or the other, not both. If it was to use BOTH ram, then you would need independent addressing (At least).

As long as there are separate Chip Select lines, there is absolutely no reason why you couldn't use both RAMs.

As a matter of fact, unless the Minimig has extra, unused address lines going to the RAM (which I doubt) then you have to use both RAMs to gain any benefit.

[Darrin]

Looki ng at other news on this thread, what that demo really needs is AmigaSYS installed on that Hardfile.

[BooBoo1200]

WOW :-D This is brilliant - Even running WHDload - As I consider other Amiga clones a joke -Well done yaqube![img align=left]http://eab.abime.net/images/smilies/xmas.gif[/img]