Unknown A1200 Accelerator Card

[sir_inferno]

Hi chaps,

So I got myself an A1200, and it has this little chappy inside.

http://img811.imageshack.us/img811/7668/imag0321f.jpg

On the rear of the card are HM514400BZ7 1Mx4 DRAM chips placed in the slots marked B1 (with B2 slots being empty).

When it's out of the Amiga, I get the purple kickstart screen and everything's fine.

When it's in with the rocker switch in the top right corner set to "RAM ON", I get a yellow screen (accelerator error?)

When it's in with the rocker switch set to "RAM OFF/TEST", I get nothing. No screen, not even the yellow one, nor the different shades of grey you normally get.

So rather than tinker about with every switch and risk breaking something, I figured I'd ask for some help. In case the picture isn't clear enough, these are the user-configurable gubbins:

-RAM ON or RAM OFF/TEST [presumably this just turns the RAM on the card on or off?]
-DRAM CHIP SIZE (1Mx4 or 256kx4) [currently set on #1, which makes sense]
-BUS WIDTH (32BIT or 16BIT) [currently set at 16 bit]
-BANK ENABLE (B1 or B1&2) [currently set on #1, which makes sense]
-Feature (FR or PCM) [currently set on FR]
-FPU (ON or OFF) [currently set ON, presumably this just controls the co-processor?)
-FPU CLOCK SELECT (A1200 CLOCK or CLOCK MODULE) [real-time clock? there's a battery on the rear of the card]

Are they set correctly as far as you guys can tell?

Thanks!

[sir_inferno]

BUS WIDTH should be set to 32 bit.

Thanks! With the RAM switch set to OFF/TEST it now boots fine.

With the RAM switch set to ON, though, I get the "Expansion Board Diagnostic" screen with its ominous red background telling me the board's defective (see here).

Does that narrow it down to faulty RAM chips? And if so, presumably that would mean I'm only getting the benefit of a co-processor, with no extra memory?

[sir_inferno]

FPU CLOCK SELECT (A1200 CLOCK or CLOCK MODULE)
Is likely what speed the FPU is running, either about 14Mhz which it can get from the motherboard or in this case 33Mhz that it get from the crystal just below (with an arrow pointing at it).

I'd set the FPU to off.

Why would anyone want to underclock it? Compatibility reasons? And surely turning the FPU off would negate the purpose of the board?

[sir_inferno]

Check out any damage that corrosion might have done.

Doesn't look like there's any.

http://img641.imageshack.us/img641/9821/imag0325n.jpg

You might have fitted an FPU that can't do 33MHz, maybe a 16MHz one.

Can you show us the RAM chips that are installed?

Ah that makes sense.

http://img40.imageshack.us/img40/7174/imag0324w.jpg

[sir_inferno]

Ok, so I moved the RAM switch to ON, and set the bus-width back to 16-bit and I don't get the yellow error screen anymore! I do, however, only get 2MB of fast mem reported back in sysinfo (though might this be correct, since with the bandwith halved, only half of the memory can be addressed).

32-bit bus-width with the RAM switch on still gives me the red board diagnostic screen.

[sir_inferno]

Sounds like you've got a bad RAM chip. Are they socketed or just soldered in?

Ah, bummer Socketed. I tried reseating them but to no avail.

You get 2 MB from 4x 514400 chips as far as I can count

Really? Doesn't the name (HM514400BZ7 1Mx4 DRAM) suggest that you get 1MB per chip. 4 chips, meaning 4MB?

[sir_inferno]

http://docs.google.com/viewer?a=v&q=cache:zVpFw_-TDsAJ:people.engr.ncsu.edu/efg/506/sum99/001/hw1-mem-solutions.pdf+1m+x4+memory+configuration+how+much&hl=fi&gl=fi&pid=bl&srcid=ADGEESgkBU5PXRDf_ywN56Q0HWoLhfz-HqwJ_j8FtV4cPg3eKUjAK2Iyh4IZPiGbYErLjH_xdFOURPCxRc3XNxFzRFQdAKLta0E6f1Q2fbmw8tqgS7AIyYLvWI1jbNttS2GoK0QVV2l3&sig=AHIEtbTzKkK05xMsANAEN20jqBCXa_mAGg

I'll take your word for it.

So the 2MB reading is correct, in which case the only matter outstanding is the 16 vs 32 bit bus width.

Any solutions? Or if not, will there be any huge impact on performance?