Recent content by sunder

Lisa was never designed to use the 68010, this was just a (somewhat) recent experiment done by James Denton to see if it's possible. A 68010 would have had better MMU support and have been faster, however, there are some very specific timing dependent bits of code, such as reading of the serial...

I mean, I wouldn't really use a Lisa to run Mac software anymore* so it's, uh, like comparing apples to oranges, if you'll excuse the pun. MacWorks may well be far more efficient at running a single application vs multiple ones. However, I'd also point out that most of the time, all computers...

Hi Tom, sadly no Lisa 3, a color Lisa, or the Whopper made it past a thought exercise phase, so it's all speculation at this point. You are correct, technically you can point the video buffer on a Lisa anywhere within the physical 2MB RAM space, outside of the MMU. So it's not just two screens...

I think you're referring to this? http://www.bitsavers.org/pdf/apple/lisa/Whopper_ERS_V2.0_Jul83.pdf

Yeah, there's a lot of weird stuff in the Lisa. The most blatant are flops that can be enabled or disabled on reads. These are used to turn on the MMU contexts and memory parity checking tests, for example. That's right, a read is actually equivalent to a write, because it only cares about...

I don't think there's anything that checks when the CPU accesses video memory, so yeah, all the time.

The video circuitry runs constantly and needs access to 32K of RAM at all times, unfortunately DRAMs at the time of the Lisa's release were not fast enough to allow the video display circuitry to share access to RAM with the CPU at 8MHz, so they slowed the CPU down. It's actually quite a lot...

This is correct, I think one of the original docs said to deserialize the LOS install disks, but I feel this is most likely incorrect as it works on previously used disks, only (some of) the tools are protected. It might even be that when the LOS floppy is inserted the OS is merely updating a...

Eh, you could have saved yourself a ton of time by looking here: https://github.com/rayarachelian/lisaem/blob/unstable/src/tools/src/los-deserialize.c There's a flag that enables the protection bit (I call it Bozo bit in the spirit of ResEdit) that once cleared will remove the copy protection...

Yeay! Glad you fixed it! Not sure if it helps or no, but I've had issues with the FloppyEmu and a 2/10. Perhaps it's firmware, but it worked well with 2/5's - I think mine was a version "B" It basically worked to start booting but not after the OS loaded. But I think from the photos, yours is...

There's a bunch of them See the schematic, it's the 74ls283 adders in schematic page: https://lisaem.sunder.net/cgi-bin/bookview2.cgi?zoom=0?page=3?book=6? The adder chips are labeled U8B, and U9B, U10B The SRAM registers for the MMU are: U8A, U9A, U10A, Also the d-flops at U11D. Basically...

Yup, installing it upside down would provide +5V to GND and GND to +5V. Sorry. :( But yeah, that address lines go to various decoders all over the Lisa. All of them go through the MMU unless SIO (Special I/O space) is specified with the special "SETUP" latch. This space is used immediately at...

So I'm unsure what that could be, but I'd guess there's an issue with the CPU board, or perhaps the connections on the motherboard. Could be anything from a filtering cap to a short, to maybe even a power supply issue where there's just enough power for one board but not both. By some chance do...

Did you try swapping slots? does it still work in the other slot? Or is it only failing with both cards in? if so that's really weird. I'm not sure what it could mean when either card works in either slot, but both together fail.

Assuming both boards are 512KB each, then, yes, only one board is being recognize. Note that the MMU is not thoroughly exercised by the boot ROM. So it's unlikely to be an issue with the MMU. The Boot ROM basically sets up the MMU to access the entire possible memory space + I/O and Boot ROM...