A500 trapdoor memory: free design

[plasmab]

Originally Posted by CRP

I have a rev 3, so I will try it.

Thanks!

There is a firmware update coming v soon that fixes this and a bunch of other bits.

[CRP]

Originally Posted by plasmab

There is a firmware update coming v soon that fixes this and a bunch of other bits.

Thanks, looking forward to it

[watman]

Hi guys!

A question regarding this expansion - how much extra mem can it give with rev8.1A mb?
I have the 4 chips version with Gary adapter that I am using now for rev5, and would like to use it in 8.1 that I have recently obtained. I assume that I will need to solder the demultiplexer chip to the MB anyway, but is there a way to get 1,5MB of extra Chipmem out of this board, so that I don't have to look for RAM chips suitable for the mainboard etc?

EDIT: I have received the answer elsewhere, this will not work with 8.1A rev MB without modification, so no answer needed. Keeping the original here in case anyone wanted to know the same thing

[katarakt]

@patzik

Do you want to share your board and layout file too so that others can do modifications based on your version ? This would be great


edit: Oh !! i found a bad trace in the layout on the 3-pin switch...this dosn't look right !!! patzik, this should be corrected:

Originally Posted by CRP

I have a rev 3, so I will try it.

Thanks!

Which firmware are you using now?. I'm about to build a full house 501 with fully populated ram. I got my TF530s working but they wont run at full speed and aren't exactly what I would call stable. sysinfo 3 tells me they are running at 13.9 mhz.. with a 50mhz crystal a bit slower than that with a 25mhz and to be honest I see no speed increase over the stock A500, they both behave identically so at least I can build them consistently not well lol.

[SukkoPera]

Originally Posted by alenppc

Certain TF530 firmware revisions (RC 1/2) don’t work with 1.5 mb slow-fast, so you have to limit it to 1mb but otherwise it works fine.

I can confirm this with the latest firmware release. 1.5mb slow still has crashes here and there, while 1mb seems very stable.

[Solo761]

Hi all, I had some Rev B.6 boards made more than half a year ago and finally got to try and assemble one few days ago.

I made one board and one gary adapter. I think (and hope) everything is soldered OK. I tried connecting the board to Rev 5 A500 motherboard (with Agnus 8375) and I get green screen.

Is gary adapter required to configure everything if I soldered all 4 memory chips? Because that's the thing I haven't installed so far. I wanted to test the board itself before soldering connector to JP2 on motherboard.

Also, do I need to cut traces between pads on JP2? As I see there's connection between middle and lower pad?

I used 72421 RTC which is supposed to have internal oscillator so that's why pads on board are empty.
Also, I've cut all traces on board and soldered jumper headers so I can configure them until I figure out what works (except ras0-rasu4-ras1 pads on the bottom, rasu4 and ras1 are "hard" connected).

Here are top and bottom of the board

[PeteAU]

Originally Posted by Solo761

Hi all, I had some Rev B.6 boards made more than half a year ago and finally got to try and assemble one few days ago.

I made one board and one gary adapter. I think (and hope) everything is soldered OK. I tried connecting the board to Rev 5 A500 motherboard (with Agnus 8375) and I get green screen.

Is gary adapter required to configure everything if I soldered all 4 memory chips? Because that's the thing I haven't installed so far. I wanted to test the board itself before soldering connector to JP2 on motherboard.

Also, do I need to cut traces between pads on JP2? As I see there's connection between middle and lower pad?

I used 72421 RTC which is supposed to have internal oscillator so that's why pads on board are empty.
Also, I've cut all traces on board and soldered jumper headers so I can configure them until I figure out what works (except ras0-rasu4-ras1 pads on the bottom, rasu4 and ras1 are "hard" connected).

Here are top and bottom of the board

If you want to test it early, it's best to do that BEFORE putting more than 1 RAM chip and the 74F139. After that, you'll need the gary adapter. I haven't looked at the circuit lately, but leaving the "cut these" jumpers joined with the 74F139 on-board might be dangerous.

A lot of people are putting jumpers for RASu1 and RASu3. You could leave the pre-link, they never need changing.

P.S. Add a C16 to your board.

[Solo761]

Well dang, thanks for the tip. I left XCAS block jumpered and forgot about "CUT THESE FOR GARY ADAPTER" part...

I removed jumpers and it seems to work, almost.
Second issue was because I'm using Kipper2k's A500 8MB IDE board and this seems to clash with this board.
After I removed it and plugged only CPU in it's socket it booted up fine. Although it shows only 512 kB chip ram. I got 1.5 MB slow, but chip remained at 512 kB.

Do I have to cut JP2 trace between lower and middle pad to get it working? So far I only connected to middle pad on JP2 and left this trace untouched (red line in the image).

*edit* found out I have to cut it. Now it shows 1 MB chip and 1.5 MB slow .

I tried connecting kipper2k's board back and now it also works. Although I have to retest that. At first glance math doesn't add up. Amiga has 512 k, I have 8 MB on kipper's board and 2 MB on memory board. That should be 10.5 MB and avail command show ~11 in total .

I'll have to run some memory test app with all enabled and with gary adapter configured to 1 MB slow. Maybe that'll fix this.

[hlide]

Originally Posted by Solo761

At first glance math doesn't add up. Amiga has 512 k, I have 8 MB on kipper's board and 2 MB on memory board. That should be 10.5 MB and avail command show ~11 in total .

Yes, I confirm you're bad in math:

10.5 * 1024 * 1024 = 11010048 bytes

[appiah4]

Just wanted to thank Pete for generously donating my Rev1 board, I thank him every time my A500 turns on and remembers the time.

[patzik]

Latest version with the corrections that were needed.

I uploaded the eagle files for who needs it, if all is ok I will also make the gerbers.

[katarakt]

I can't open it with eagle because of some errors.

[patzik]

Originally Posted by katarakt

I can't open it with eagle because of some errors.

I downloaded the file again, and it works fine for me in eagle 9.2.1

[patzik]

Latest Gerbers

[PeteAU]

Originally Posted by patzik

Latest Gerbers

Hi patzik,

I'm trying to help you out to avoid wasting boards/money on this:
- You used a different CAM file, so the ground plane changed. The margins are too tight in a few places. Look at the grounds for U1, they look a bit shitty. I had a CAM file in my original ZIP, use that.
- The trace you added near U3 blocks off the ground to the chip - it won't work.
- The trace you added for switch 3rd pin blocks the short path for ground to U2/U3 - I don't think this is very good.

If you want to do something useful, remove the jumpers for U1/U3/U4 entirely. That would simplify things and avoid confusion. Removing the pre-links is retrograde IMO. Then I would rename to jumper above U2 to say something like "A500+ (left) / A500 (right)".

[patzik]

Hi Pete, glad you checked the things I did. I did this not because I think it's 'better' but because it was requested. Personally I prefer solder jumpers, and not preconfigured as I don't like cutting into the pcb's and soldering a jumper takes maybe 2 seconds. I didn't see your cam file, and just used the one from dirtypcb, that I always use, but I don't see where U3 is blocked from ground I think it is connected.
Anyhow, I'll stop messing with your work. Better to do nothing than a @#%# job....

Originally Posted by PeteAU

Hi patzik,

I'm trying to help you out to avoid wasting boards/money on this:
- You used a different CAM file, so the ground plane changed. The margins are too tight in a few places. Look at the grounds for U1, they look a bit shitty. I had a CAM file in my original ZIP, use that.
- The trace you added near U3 blocks off the ground to the chip - it won't work.
- The trace you added for switch 3rd pin blocks the short path for ground to U2/U3 - I don't think this is very good.

If you want to do something useful, remove the jumpers for U1/U3/U4 entirely. That would simplify things and avoid confusion. Removing the pre-links is retrograde IMO. Then I would rename to jumper above U2 to say something like "A500+ (left) / A500 (right)".

A question:
Is it possible to completely disable the card or configure it for 500KB Chip and 500KB Fast.
I just want to use the internal 500KB or 500KB RAM extension for games that run on 500KB or 1MB of RAM only.

[bytestorm]

Wow.. cant belive I found this just now.. . Its so awesome of you all to share this with all of us.

After reading all pages in this thread and random other posts I do realise that I might run into trouble, but you guys could maybe set me on the right path?

I have 2 stock amiga 500 (Rev 5) that I would like to upgrade so that I can run WHDLoad.

From what I understand, the REV 5 motherboards are not that good candidates for WHDLoad since they dont have 1mb chip ram support? And both mine have the "old" agnus 8371.

Or is the rev 5 still usable if my target is WHDLoad?
With this card + gary adapter, what would be my max spec Ramwise, if not changing agnus?

Thanks in advance!

btw, any DIY kits of the latest version availible for sale?

[majinga]

Depends on the KS version.
With KS 1.2, you can have 1 MB chip + 1MB slow.
With KS 1.3 or higher, 1 MB chip + 1.5 slow