LisaList2

Quote from: AlexTheCat123 on February 15, 2026, 11:05:45 PMwonder how they came up with the packtable that shipped with LOS? I'm guesing they analyzed earlier versions of the OS (or maybe the Monitor) and just threw the most commonly-occurring words in there?

They might even have looked at exactly what the Pascal compiler's code generator can output, since it's only ever really going to use a subset of instructions and addressing modes anyway.

It also doesn't seem like it'd be very difficult at all to modify the binary loader to use a packtable found inside a file to unpack any packed code inside of it. There's no code to do that currently (unpacking always passes the system packtable) but it'd just be a matter of keeping track of the object during the initial scan through the file and then passing it to UNPACKCODE instead of the system packtable.

Quote from: ried on February 23, 2026, 09:13:36 PMIt is surprising that the Lisa's clock required so much power. The Macintosh 128k used one 4.5v 600mAh battery and kept the time for much longer (1-2 years?) when unplugged.

A Macintosh has an integrated RTC chip that needs a couple of microamps. The Lisa uses a COPS4 microcontroller that does not provide any significant power saving features.

Quote from: ried on February 23, 2026, 09:13:36 PMIt is surprising that the Lisa's clock required so much power. The Macintosh 128k used one 4.5v 600mAh battery and kept the time for much longer (1-2 years?) when unplugged.

Yes, I was hoping a stack of coin cells would be a safe and usable replacement.

Typical 68k accelerators use local memory. This means you have a computer inside the computer that runs at high speed. For external access, such as input/output (I/O) or video, the speed is either slowed down (synchronous access) or the accelerator waits for a DTACK signal from the memory or peripheral (asynchronous access).

There was usually a GAL that defined the address space, i.e., where the CPU had to slow down. This made it easy to adapt the board to Amiga, Atari, and Macintosh computers.

I assume the XLerator works in a similar way.

You know, I was recently wondering the same thing. Some time ago I picked up a Macintosh Plus with a 16MHz "Brainstorm Accelerator" installed and wondered what it might take to get that part working in a Lisa. It looks to be quite simple.

I'm sure there are quite a few Lisa-specific complications to consider, and sigma7's XLerator is a much more robust and capable solution with additional RAM, SCSI, FPU support and so on.

Still, I wonder. 

I know about the unobtainable proprietary Lisa XLerator card and the relevant discussion at https://lisalist2.com/index.php?topic=594.0

But I wonder if anyone was able to speed up their Lisa by replacing just the CPU and the clock generator  with faster one?

I am sure this has been discussed in the past and also at 68kmla.org, but I can't find a good answer.

People mention the custom video refresh timings and the slow RAM, but somehow XLerator was able to overcome them. It seems that it is using the Lisa RAM for video buffer, and its own faster on-board RAM for system memory. 

Relevant links:

https://bitsavers.org/pdf/apple/lisa/hardware/1983_Whopper/Whopper_ERS_V2.0_Jul83.pdf describes a Lisa "Whopper" project  at Apple that never got completed. They wanted to run the CPU at 10 MHz: "A 10 MHz CPU clock has been selected because 10MHz  is 1/3 the 30MHZ clock used in the video circuit".

Why Lisa didn't use 8MHz 68000? https://68kmla.org/bb/threads/why-lisa-didnt-use-8mhz-68000.39609/

A 68010 in a Lisa? https://lisalist2.com/index.php?topic=43.0

It is surprising that the Lisa's clock required so much power. The Macintosh 128k used one 4.5v 600mAh battery and kept the time for much longer (1-2 years?) when unplugged.

As sigma7 said, the Lisa RTC depends on the Lisa being plugged-in to AC power.  The battery backup on the original IO board will only maintain the time for up to 10 hours.  If you had a minor power outage or just un-plugged your Lisa to move it to another room this worked well.  If you unplugged your Lisa at the end of the day, and plugged it in the next morning, the batteries would be dead and your clock was reset.  It seemed like Apple recognized this was pretty useless and they removed the batteries from the 2/10 IO board.

Rick



 

Fantastic accomplishment and amazing contribution!

Thank you!

Quote from: sigma7 on February 22, 2026, 05:35:20 PMso there isn't a really trivial way to connect it.

As long as the Lisa is connected to AC power, the time should be retained, so if using a power bar to eg. turn off peripherals, perhaps you can power the Lisa separately.

Thanks!