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That's the thing, we can remap the RAM kind of like an MMU, but it's totally nonstandard, so there is no existing app that can do it. But a thorough study/decompilation of Compact Virtual 3.0 would be very useful since we could then replace the parts that use the MMU with code for a different...

@zone66x Wow, this looks like a great project. It would be good if we can totally relocate the ROM and also the SCSI chip and framebuffer pointers to make room for a bunch of contiguous RAM. @Snial Oops didn't see your post. This is good progress! But we still face the big task of modifying the...

At Garrett's Workshop we have long been thinking of making a SCSI device but one issue we have is the SCSI edge rate spec. I think the spec demands a 5 ns edge rate or slower to prevent the signal from ringing in all of the stubs on the drive boards, but LVT-series chips have something like 0.5...

Ooh you made me realize me something I said was wrong. LVT series can sink 64 mA and source 32 mA, opposite of what you said. So the resistance when driving high is more like 10-20 ohms, not 5-8 ohms like I said. This makes the problem a bit better but still not great. I think there's kinda two...

@GRudolf94 Nice work on the switching regulator layout. Looks like you kept the "hot loop" pretty small. Lots of new-manufacture gizmos don't get that right and are probably emitting a ton of EMI needlessly. But what about those ‘245s? Those look like they're driving the SCSI data and control...

Accelerator is working with the new memory mapping: Sorta obtuse to read but the gist is that the A23 and A22 address lines going from the accelerator to the Mac's motherboard are forced to 0 when the address is in the $6XXXXX, $700000-$7EFFFF, and $8XXXXX range. This maps these ranges to RAM...

Seems like the code for starting an application is mostly in Processes.c (from the leaked "Super Mario" sources): https://github.com/elliotnunn/supermario/blob/9dd3c4bef84df2ea30f5ec2c5e97b043e8267b3f/base/SuperMarioProj.1994-02-09/ProcessMgr/Processes.c NewProcess(...) calls...

I don't think it's a good idea to try and put a hole right in the middle of an application partition. I understand you can do this by putting a big nonrelocatable block in the middle right before the app starts running, but semantically it's not in line with the application lifecycle model. The...

Okay I guess A5 world and obviously the stack are app specific, but still, whatever goes in this highmem area would probably benefit from being in the fast RAM. I just read the memory management chapter in Inside Macintosh but it doesn't say much about how the OS creates the individual...

Do we have to have an INIT or ROM patch at all? It seems worse to make RAM contiguous at boot because then "highmem," A5 world, and the stack end up in the slow RAM. Instead we should let that stuff go from 0x3FFFFF downwards at boot. Then after the system is fully booted we should patch the...

I have a prototype open-source 68HC000-based accelerator made in partnership with Garrett’s Workshop that can do what’s described here. The accelerator has 4 MB of onboard fast RAM for the main 4 MB of RAM at $000000-$3FFFFF and does not use motherboard RAM except for the video/sound buffers...

The other day I was itching to make the right angle PDS adapters for my 6100 and 610 but I wasn't sure of the exact dimensions. There seem to be several types and I dunno which dimensions (in terms of where to position the connector on the right angle board) are applicable to which adapters...

This guy sells one: https://www.tinkerboy.xyz/product/tinkerboy-usb-mouse-to-mac-converter-adapter-for-macintosh-with-db9-mouse-port/ Not too expensive and the case design is quite professional! Nobody seems to be talking about it; the designer posted on AppleFritter several times, but last I...

It’s complicated...I puzzled it out a bit more. The LC II has no less than four signals called reset. Two “power-on reset” signals are generated by U12, which is an MC34064 “undervoltage detection chip.” U12’s function is to pulse those reset signals when the power is turned on or recovers from...

Wow! I did not know this. I thought it would not be possible to dump it from the Mac. Maybe the Egret is the same as one of these 6805 MCUs, and if so, we could burn another: http://www.bitsavers.org/components/motorola/6805/Single_Chip_Microcontrollers.pdf The Egret has 28 pins and evidently...

The system runs when reset is high (above 2.0 V) and doesn't run when reset is low (below 0.8 V). When the computer powers on, reset should be low, but then it should go high and that in turn causes the processor to work, startup chime, etc. So if it's always low or going back and forth, the...

Looking at the schematic briefly, it seems that U10 6805 microcontroller drives the system reset low, since the physical reset button on the LC II is hooked up to the 6805's reset input. I would check if the system reset (available on the PDS slot) is ever going high with a multimeter or...

Good news! The 8MB SIMM works! Thanks to all of the testers for their diligent work on the 2 MB SIMM! @JDW uncovered a significant defect in the 2 MB SIMM which is possibly the reason it didn’t work in his SE/30. Fortunately the 8 MB SIMM doesn’t have this issue, so hopefully that will fix...

Thanks! What I mean is a little different than what you’re saying though. I’m talking about when an application has a DMA disk card read into an a buffer owned by the app. This buffer will often be in expansion RAM. So for a read operation that moves a disk block from the card into an...

Oops, didn't see the posts on page 4 earlier when I replied... Ooh, I will look into MindExpander, including just personally. Hm yes, I would like to, but BareBones still exists so I will have to ask them. Hopefully they agree. Unfortunately it's still ~600 kB, which is a lot heavier than...