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Open Source 68-Pin 512kb VRAM

mmu_man

Well-known member
Hmm why only PDF for the schematics?
The "source" in Open Source means source, not a screengrab of it :p
 

mmu_man

Well-known member
Also, putting zip files in an SCM kinda defeats the purpose of it, you can't diff it (yes, with git it's even possible to visually diff gerber files)… But for that you need to have them directly in.

It will also make the git repo smaller since git will only store the text diff between versions, not the whole zip each time.

Anyway, nice project!
 
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Stephen

Well-known member
Hmm why only PDF for the schematics?
The "source" in Open Source means source, not a screengrab of it :p
The project was designed in EasyEDA. Thanks for your feedback!

edit: EasyEDA source JSON file is in the "gerbers" directory and the first paragraph of the repo's readme has a link to the open hardware source, which includes access to the schematic sources. (y)
 
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mmu_man

Well-known member
Ah ok so the source is available but on some cloud instead of the git repo. At least it's public. Let's just hope the cloud doesn't vanish :)
 

Stephen

Well-known member
Ah ok so the source is available but on some cloud instead of the git repo. At least it's public. Let's just hope the cloud doesn't vanish :)
Is there something particularly grievous about the project I've shared? Your responses sound very snarky!

The EasyEDA source files are in the repo. There are tools to convert the EasyEDA files to other formats (e.g., KiCad). Because I do not use other tools I cannot confirm the accuracy of conversions, and as a result I have chosen not include converted formats.

If anyone would like to submit converted formats I would gladly upload myself or approve PRs!
 

Iesca

Well-known member
I've released the schematics, gerbers, and PCB files for a VRAM version based on the Apple 820-0605-A 512kb VRAM (GitHub). If you appreciate this project I encourage you to star the GitHub repository and share it with friends.
This is awesome! Would be neat to also have a 256k version for those machines (like the LCIII, perhaps others?) that can only take the smaller of the two.
 

mmu_man

Well-known member
Is there something particularly grievous about the project I've shared? Your responses sound very snarky!
Oh no it's not about you or your project, I want it to be useful to the most people, I just genuinely don't trust online services to be available for eternity so I was concerned about long term. Sorry if that sounded mean.

The EasyEDA source files are in the repo. There are tools to convert the EasyEDA files to other formats (e.g., KiCad). Because I do not use other tools I cannot confirm the accuracy of conversions, and as a result I have chosen not include converted formats.

If anyone would like to submit converted formats I would gladly upload myself or approve PRs!
I don't have KiCAD installed on my new laptop yet but I can have a try on the old one.
 

olePigeon

Well-known member
Excellent work. I like seeing new homebrews. Would love some GWorld RAM, too. Seems to be unobtanium.
 

Stephen

Well-known member
I don't have KiCAD installed on my new laptop yet but I can have a try on the old one.
Appreciate it!
Excellent work. I like seeing new homebrews. Would love some GWorld RAM, too. Seems to be unobtanium.
Do you have more information I can refer to? Could be interesting.
This is awesome! Would be neat to also have a 256k version for those machines (like the LCIII, perhaps others?) that can only take the smaller of the two.
I believe the 512k is backward compatible with 256k; only the first half of the memory gets mapped. Admittedly, I don't know for certain.
 

olePigeon

Well-known member
@Stephen It's a special 1MB 100ns 68-pin SIMM. Despite what some websites claim, it is NOT the same type of RAM as a IIfx. They are not compatible.

I wish I could offer you more information, but the reality is that you'd need to get your hands on an actual 1MB SIMM for an 8•24 GC video card. Since they're so rare, I doubt anyone would want to donate one to be reverse engineered. :(
 

trag

Well-known member
I've released the schematics, gerbers, and PCB files for a VRAM version based on the Apple 820-0605-A 512kb VRAM (GitHub). If you appreciate this project I encourage you to star the GitHub repository and share it with friends.
Thank you for sharing. This is a nice project. Have you considered variations for different widths of VRAM chips. They seem to come in three different widths.
 

Trash80toHP_Mini

NIGHT STALKER
Nice project, has anyone looked through the Designing Cards and Drivers series for Apple specs on the various memory interfaces? DevNotes are also good sources, I found the full spec for the PowerBook 100 memory modules in its DevNote. I'd imagine VRAM and GWorld RAM would be spec'd somewhere in the developer docs as well?
 
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