A500 trapdoor memory: free design

[katarakt]

Thank you very much PeteAU, this will help a lot

[PeteAU]

Got Mathesar's improved Garry adapter. Looks good, just got to find time to build it

[katarakt]

Would be great if you can update your eagle file with the improved gary adapter

[dragmar]

Hello, Gary's plate and adapter are starting. I used 74F139 and 74HCT00.
SYSTEST shows errors.

what is wrong?


REV 5, MOS 8371, kickstart 1.3, JP1: UP, JP2: UP, JP3: DOWN

[demolition]

Originally Posted by dragmar

REV 5, MOS 8371, kickstart 1.2, JP1: UP, JP2: UP, JP3: DOWN

I thought that KS1.2 did not support 1.5MB slow mem config but you had to go with either 1MB or 1.8(2)MB?

[dragmar]

No, I installed kickstart 1.3, my mistake in the description.

[Mathesar]

Try setting the enable jumper on the RAM board.
I think the RAM chip selection on the Gary adapter goes wrong if you don't.

Also, to check that the enable jumper is the culprit, try setting JP3 to UP (1.0mb fast) to check if the problem goes away.

[PeteAU]

Here's my stab at dragmar's possible problem:

Did you cut the links "cut these for gary adapter" right?

How is JP2 on A500 motherboard, back to default right?

Maybe U3 really has 1 bad solder joint?

[dragmar]

try setting JP3 to UP (1.0mb fast)

Same symptom

Maybe U3 really has 1 bad solder joint?

The best part is that I tested diagrom and showed that memory ok

How is JP2 on A500 motherboard, back to default right?

Yes

Did you cut the links "cut these for gary adapter" right?

I do not understand

[Mathesar]

There is a 4 jumper block on the main ram board.
Each of the jumpers is connected on the board via copper traces.
There are thus 4 traces on total. These 4 traces must be cut for the Gary adapter to work.

[dragmar]

thanks @Mathesar, @PeteAU
it works, cut four lines, my bad

Rev 6a, KS1,3 and KS3.1

Rev 5, next post

[dragmar]

Rev 5a, mos 8371, ks 1.3
The same extension that I tested Amiga 500 Rev 6a

TESTED:
Single memory CHIP RAM - OK
Single memory SLOW RAM - OK

but, DIRECT MEOMRY SCAN - FAILED. I do not know why?.

[PeteAU]

Originally Posted by dragmar

Rev 5a, mos 8371, ks 1.3
The same extension that I tested Amiga 500 Rev 6a

TESTED:
Single memory CHIP RAM - OK
Single memory SLOW RAM - OK

but, DIRECT MEOMRY SCAN - FAILED. I do not know why?.

How about kickstart memory scan, it succeeds?

[dragmar]

Yes.
Slow Ram i chip ram

[alenppc]

This is just too friggin' cool

Finally got the rams from China and built PeteAU's expansion along with Mathesar's Gary adapter, connected everything and boom: it all worked on the very first attempt!

My humble A500 now has 1 Mb Chip, 1.5 MB Slow-Fast and 2 MB on the TF530. It's a VERY usable system now.

Amazing. Thank you guys, this rocks!!! You rock!

[Mathesar]

That is a nice A500!
These DIY expansions are cool right?
Waaaay more fun then buying something of the shelf

[alenppc]

Originally Posted by Mathesar

That is a nice A500!
These DIY expansions are cool right?
Waaaay more fun then buying something of the shelf

Indeed, so much fun having it come to life. To be honest, I didn't expect this one to boot straight up without issues. I thought I'd have to spend time debugging it, but instead it all booted at first try. So happy!

[PeteAU]

Originally Posted by alenppc

Indeed, so much fun having it come to life. To be honest, I didn't expect this one to boot straight up without issues. I thought I'd have to spend time debugging it, but instead it all booted at first try. So happy!

You missed out on the fun of green screens and such like.
So, does kickstart know to prioritise the fast ram ahead of the 1.5mb slow ram?
Close up photo of your boards?

[alenppc]

Yes, the TF530 RAM has the highest priority, followed by slow-fast and ultimately Chip RAM. I can take close up pics tonight when I get home.

[alenppc]

So the chip ram has the -10 priority, the slow fast is -5 and TF 530 is priority 0.

Here's a pic of the whole contraption with relocator and all that. Now I gotta hunt all the RTC parts.