2MB A500/A500+ trapdoor RAM

[cmorley]

Hello All,


I'm a new member here so appologies if I've posted in the wrong section. I've been active doing upgrades for other 8-bit machines and now I've done my first upgrade for thw 16bit Amiga 500 & 500+


It's a 2MB card with Gary adapter. I've tested it on my rev3, rev5 and 6A A500 and 8A A500+. It needs a mod to work on the rev3 - extra capacitor to filter _CCK. Works without the Gary adapter too for 512K on an 500 & 1MB chip on a 500+.


Wire mods are needed to get the full 2MB.
A500 +0.5MB chip, +1.5MB slow/ranger
A500+ +1MB chip, +1MB slow/ranger



Kickstart 1.3+ is required for the Gary adapter to work (won't boot with 1.2). A 1MB ECS Agnus is required for 1MB on an A500.



Hunting aroung I found A-Train and SimAnt seem to be good tests as these need more chip RAM and slow RAM to load in hi-resolution mode. Anyone got any more suggestions for RAM intensive programs to try?


Is it better to include links to pictures from an external site or uplead them as attachments? I'll edit the post as necessary...


All pictures are here: http://www.boobip.com/hardware/A500_2MB/photos


Chris



Memory board + Gary adapter:



Close up top:



Close up bottom:




In A500 with chip RAM mod:



In A500+ with mod:

[PeteAU]

Hi cmorley,

I guess you're twiddling the A9 during RAS/CAS to get 4 different regions in the RAM chip, hence the CPLD. Then you delay the RAS/CAS to the chip to give enough setup time for the "new" A9?

The post is all a promotion for the boards you're about to sell though, not even a nugget for free?

May I ask, will you be hand assembling them? The 96 pins on the Gary will feel like slave labour eventually.

Anyway, nice board, I like it.

[cmorley]

Yes the PLD handles the A9 generation from the address pins coming from Gary and !BLIT. CAS is delayed slightly by a few ns to guarantee A9 CAS setup. The PLD switches A9 generation between A500/A500+ depending on the jumper input. So it then maps 4x 512K blocks into the Amiga address space.

The PLD also handles DRAM refresh. The PLD is a vanilla 22V10C from Atmel. They still make them and they are readily available.

The CAS delay is only actually needed on A500 rev3 & rev5... the RAM chip has a zero setup time for CAS address & difference in timing from the EMI filtering on the 6A and 8A means it works.

The series resisitors are (SMD 4x arrays between RAM and connector) are only needed for rev5 and rev3 too... so electrically noisy compared to the later rev 6A.

And the !CCK clock needs filtering on a rev3 too (Commodore added this to the 6A). I use the !CCK for DRAM refresh.

Yes, hand assembling. I don't mind that... I don't sell much stuff. Cleaning is more of a pain IMO.

Chris

Edit: for anyone wondering why the series resistors are needed on 3 & 5 it is because without the voltage undershoot on negative edges goes below -2v which is the datasheet limit for the RAM and the PLD pin inputs. The chips will prematurely die without it. rev 3&5 are worse than 6A because the motherboard layout is worse. So a board will function without the series resistors but the chips will die (at some point). Hence why Commodore fitted them to A501 even though they don't seem necessary on the face of it.

[Mathesar]

Nice board indeed.
Are you aware of Pete's open-source version?


See http://eab.abime.net/showthread.php?t=85395

[cmorley]

Yes. I found this forum by way of Google and that thread

Great thread & project. My stuff is aimed more at the people who want a new upgrade but don't have the kit to make it themselves or indeed don't want to!


BTW... I had to buy a lot of 56 pin connectors. The MOQ will make you cry! I can make some available to home brewers in Europe if anyone is interested in that?

[Mathesar]

About testing;
I usually try to open some multiple programs in Workbench to fill up the ram.
You could for example load up hippoplayer and load a large modfile to use all the chipram, open diropus, dpaint, etc. You can also copy some stuff to ram:

Also, WHDload games are good test programs!

[redblade]

Wow. Looks nice, I should have studied electrical engineering instead of mechanical

[katarakt]

Cool little ram expansion

[Clamshell]

And it is working in A500+ with Chip and Slow ram?

[cmorley]

Yes it works well in an A500+. You need the Gary adapter and the wire mods to get slow RAM on the A500+.

The result is 2MB chip + 1MB slow

[Photon]

This is brilliant. I don't have an A500+ because of the "no internal fastmem possible*" problem. Not even Jens' ACE2 solves that. But you did! So I might get one and one of these. How do I order?

If you want games then most 1991+ Digital Illusions and Team 17 titles check for slowmem and allocates it, I think. Maybe also some other multidisk games do.

But if you want a burn-in test, my Apollo Bus Test should work fine on all Amigas. It simply shovels tons of data across any connector from chipmem to non-chipmem, checking for overclock issues vs RAM speeds or poor connector contact. It runs until it freezes (or not=OK), an hour burn-in should be plenty enough considering the connector type and no overclock.

It's better and more strict test since games can crash for reasons other than your Amiga setup being wrong as we know. I also trust this MemTest.

*=asterisk.

[cmorley]

Originally Posted by Photon

This is brilliant. I don't have an A500+ because of the "no internal fastmem possible*" problem. Not even Jens' ACE2 solves that. But you did! So I might get one and one of these. How do I order?

My solution needs a track cut/pin lift and 2 fly leads soldering if you want the A500+ slow RAM option - so not perfect.

If you want one you can PM me or email me (contact on the website). I usually have stock listed on eBay and amibay.

[Photon]

Top stuff! You have PM. Do you stock the RTC chips?

[cmorley]

I don't stock the RTC chips. I can't compete on price with the eBay sellers. The B spec chip can often be bought for less than €2.

[MageMaster]

I got this and tried to install the gary chip adapter and for whatever reason had problems and the machine only wanted to boot to a yellow screen, or get a nosync on the monitor.

Not sure If I really messed things up or not. Still had problems after removal. I changed to a different 500+ board and still had issues. I'm currently using another trapdoor ram to get an extra 1Meg.

This is OT but I have to figure out how to get a stable machine with my accelerator stuff installed.

[MageMaster]

With cmorley's superb support I was able to get my "A500+" that was actually an 8A 512k machine working. I have yet to install the Gary adapter again and may not.

Reseating the Gary chip again fixed the yellow boot.

Many thanks for the Great support and I would buy from him again!!

MageMaster

[CRP]

Hi, I have an A500 rev 6 with a TF530 accelerator card and an A501. The latter is set as chip mem with the JP2/JP7 mod. With this setup I have 1MB of chip memory and 2 MB of fast memory.
Has anybody tried to expand memory further with this Gary-adapter board? Is it compatible with the TF530?

Thanks

[cmorley]

I honestly don't know as I don't have a TF530. I know plasmab has spent a huge amount of effort to make the TF boards compatible with other hardware.


Buyers have confirmed it working with the Wicher and 2MB MegAChip. Also works with the ACA500plus but not recommended as that fakes slow RAM. Not been told about the TF boards though.



Has anyone tried it?

Edit: Plasmab kindly sent me a PM. 1.5MB slow is confirmed working on the TF534 and a project to update the TF530 is in progress.

[project23]

Originally Posted by CRP

Hi, I have an A500 rev 6 with a TF530 accelerator card and an A501. The latter is set as chip mem with the JP2/JP7 mod. With this setup I have 1MB of chip memory and 2 MB of fast memory.
Has anybody tried to expand memory further with this Gary-adapter board? Is it compatible with the TF530?

Thanks

EDIT: Before reading this make sure you've read the edit to the reply above - it has the answer you're looking for.

Take a look here:

https://www.amigacoding.com/index.php/Amiga_memory_map

The 530 starts in the Z2 space. (I don't know if he's released a firmware moving it to the Z3 space, but FYI the 534 will have it in the Z3 space). So I don't think there are memory address overlap issues - notice the 'slow fast ram' is in a separate address area. I think from reading the 530 thread that problems arise as a result of the 030 cache - but I don't know if or how this applies to you. I'll have a read and see what I can understand and get back to you, unless someone more knowledgeable does.

John

EDIT: So far what I can say is the 512k A500 expansion or 1mb A500+ expansion work fine as they get added as chipmem. It's the slowmem part that I think may or may not present a problem. Still reading.

[project23]

Originally Posted by cmorley

Edit: Plasmab kindly sent me a PM. 1.5MB slow is confirmed working on the TF534 and a project to update the TF530 is in progress.

Only just seen this edit, good stuff!

So as it stands I guess a TF530 will work as I mention in my edit, and when the 534 firmware gets backported to the 530 the slowmem should work too.