A500 2MB expansion AlfaData RA5-2M

[fc.studio]

My old A500 has this expansion. I got it for free in 1995 without instructions.

On reading amiga.resource.cx I found that is possible to have 1MB chip ram instead of 512KB. I know that jumper on JP2 allows to switch on/off the board. Remaing JP3 has two jumpers opened. I would try to close these but I wouldn't want to get serious damages.

Does anyone know how to set jumpers on it?

I made mistake. GURU screen appeared and that's all, if so make it back as it was and start again.
My A500 still working!

This could help you:
rev. 5? 6a
---------------------------------------------------------------
JP1 yes yes Connects reset timer (NE555) to main reset
JP2 yes yes Maps A501 at $C00000 or $80000
JP3 yes yes Swaps _CAS of RAM banks (of use for test purposes)
JP4 no yes 8371 Agnus : TEST line [solder closed !!]
8372a Agnus : PAL/NTSC video mode select
JP5 no yes 28MHz base clock to Agnus
JP6 no yes 7MHz clock on pin 7 of expansion connector
JP7a no yes Controls _EXRAM to Gary
JP7b no yes CIA tick from VSYNC or pin 32 of A501 (default VSYNC)
JP8 no yes LPEN from FIRE0 or FIRE1
JP9 no no ??? A non-existent jumper. Future Rev. 7 ???
JP10a no yes Connects AUDIN to pin 18 of serial port
JP10b no yes Connects AUDOUT to pin 11 of RS232 port
JP11 no yes Connects CSYNC to BCSYNC or video hybrid
-----------------------------------------------------------------
So, if you connect center and upper pin of JP2 you get 512K+512K.
Center and down = 1MB chip.

Try to google for details.

[Jope]

JP7a must also be cut, or alternately you must turn the ram expansion's switch to off if you want 1MB chip.

[whiteb]

On a Rev 6a, Yes the JP2 upper and middle jumpered turns the 512 chip and the first 512 from trapdoor into 1MB chip.

But my A500 is unique, it has a trapdoor 4MB expansion, and the three pads on JP2 have to be severed, and a cable from the centre pad to a circuitboard on the gary. The expansion does support memory mapping up to 2MB of the expansion into Chip (2MB agnus required).

It was a rare expansion made in Australia, utilising 4 x 30 pin 1mb simms. (And I have still got it.) It was called Axram 4.

[whiteb]

Originally Posted by Jope

JP7a must also be cut, or alternately you must turn the ram expansion's switch to off if you want 1MB chip.

Hmmmmmm, I'll have to dig out my 4MB expansion manual, its been a while since i took a stanley knife to an A500 motherboard.

[edit] okay, the trapdoor expansion I have, does NOT mention the need for JP7a to be cut, it does require however JP2, JP3 and JP5 depending on which setup you wanted.

JP3 and JP5 are required for 2MB Agnus operation, and mapping out 1.5MB of the expansion out to make 2MB chip, and the remaining 1.5 our to Fastram.

[fc.studio]

I thought I could get 1MB chip by using the JP3 jumpers on the expansion board only. I continue to unknow the meaning of this JP3, however you gave me useful advices. Thanks everyone.

[Striker01]

Hi folks,
I have the AlfaData RA5-2M Expansion card working in my Amiga 500.
I can provide boxshots and a scan of the manual if you need.
Unfortunately the red driver disk I got with it has read/write errors.
I rescued all the data apart from the most important file EFRAM.
(the icon file EFRAM.info is fine)
Can anyone please send me this file?
I need it to use the whole 2MB instead of 1.8MB.
Thank you very much in advance,
Reini

[amigoun]

I have this card also and I would like to ask, is it possible to use it on A500+ (motherboard rev 8a)? When used with A500 it gives me 1,8 Slow RAM, but on A500+ it doesnt add any RAM. And I also do not know the meaning of the jumpers on the card.

[demolition]

I don't think it can work with a 500+, at least not without doing several modifications on the motherboard. I have the same expansion and also tried it in my 500+ without luck. The 500+ is only meant to take 1MB chip in the trapdoor.

The jumpers are mainly to configure the amount of memory that you have installed. I have the manual for it, but it can also to be found online.

[amigoun]

If it is a matter of adding few jumpers and changing their positiion, I would do it. There is some guides how to upgrade rev 6 to 1MB chip, so there must be a way to downgrade rev 8a to accept slow ram in trapdoor. But I am not sure because A500+ already carries 1MB RAM.

[demolition]

I did look into it a little bit and it seemed a lot more complicated than the Rev 6 chip fix so I figured it wasn't worth it. I think you also need to add some logic to generate the chip select for the $C00000 address space since it is not used in the 500+.

Regarding the late A500 models which had a Rev 8 (500+) motherboard, I think it was also not possible to get $C00000 memory through the trapdoor?

[amigoun]

That is a pity. But thanks for explaining. I was thinking of downgrading A500+ because of running with AR3. Now I know I need to keep both A500 and A500+
I wonder if Kippers A508 could run with AR3, maybe if somehow limited to 2MB?

[demolition]

AR MkIII surely doesn't work with Kipper's expansion card, at least not in the default 8MB configuration. I tested it in my 500+ with it and it just produced some weird colors on the screen and weird sounds from the floppy drive which eventually got its head stuck at the end so I had to open it to physically move it back. AR3 doesn't work with many non-standard memory configurations. The latest revision of the AR3 will work (ish) with a plain 1MB A500+ however.

I'd also suggest to use this expansion in a plain A500 to use with AR3 and then use Kipper's expansion in the 500+. You could then add an external Gotek drive on the 500 for convenience. This is also how I have it.

[amigoun]

Good to know, thanks again. If you eventualy have the scan of the RA5-2M manual it would be great, I had no luck finding it anywhere on the web.

[demolition]

I thought it was on BBOAH or one of the others, but I can't find it now either. I can make a scan for you. I do remember that the manual is not very clear on what the jumpers do, but surely it is better than nothing.

I know this board exists in two versions, one with a CPU board (in addition to the Gary board) and one without. My version does not have the CPU board. With the CPU adapter, it can be configured to add 512kB chip mem and 1.5MB slow mem instead of 1.8MB slow, which would be very useful in a plain 500 so you could have 1MB chip + 1.5MB slow.

[demolition]

I needed the manual for this card a couple of days ago and remembered this thread. I still couldn't find it online, so I scanned it and here it is for posterity's sake.