Mar 17, 2020.
Want to know why I'm doing this? Click here.Ever wanted to see a Lisa's internals? Click here.Need Lisa Documentation? Click here.Curious about how the emulator is designed? Here are the project docs.Impatient? Click here to see the status of the emulator.And here to find out what's left to be doneLisa The Painful OstWant to find other Lisa sites? Click here.(Except maybe for UAE)
To make things even more complex, there are special memory addresses that turn on or shut off various flip flops. For example a memory parity error detector, a video scan line interrupt, and the MMU. The VIA's are not identical in access. One lives in offset of two bytes, the other in an offset of 4 bytes. The 6504's 1024 bytes of memory is battery backed up (this is what the four NiCAD AA's on the I/O board are for.) The 6504's address space is available to the 68000, but in two byte skips as opposed to linearly. That is memory addresses 0,1,2,3 on the 6504 are 1,3,5,7 on the 68000.
The video circuitry is fairly simple - a dumb frame buffer that shares its memory with the Lisa's memory space. As such another memory area register can be changed to 'page' through the various memory areas.
Luckily, unlike the Mac, the Lisa's (68000) ROM isn't used for much except the POST (Power On Self Test) and booting. Though it is possible for a Lisa Operating system to access the ROM, the functions it would call are limited to reading blocks off the floppy or Profile.
Yes, the Lisa does support at least three operating systems: Lisa 7/7, MacWorks (which with a bit of hardware an RAM can run upto System 7.5), and Microsoft Xenix (yes, Microsoft Xenix, not SCO: This was before Microsoft spun SCO off!) I've read on other web pages that there was a port of CP/M to the Lisa CP/M 68, but I don't have that OS. I've also seen one refrence to something called UniPlus which is supposedly a Unix SRV implementation. DTC mentioned that this later might have become A/UX... Though I'm not 100% sure, it's likely that either www.unipress.com or www.uniplus.com is the author.
As to how I got started on the project: I went on the web and searched for Lisa and Emulator and found many web pages related to the Lisa. I eventually came across one that mentioned that David T. Craig had lots and lots of Lisa documentation, and so I contacted him. He's been an invaluable resource... This project would have been close to impossible without his Docs. I just wish more people took his example and saved any technical internal docs about hardware they may have. I wish to write a Xerox Star and/or Altos emulator, but I just can't find enough detailed docs!
Actually, the emulator works and IS available for download, at the downloads page!Here lies obsolete project documentation, which you'd have to be insane to believe.The links page has moved to the LisaFAQ instead Local Mirrors of dead Lisa SitesIf you own these, or know where the owners have moved to please let me know. Lisa The Painful Wiki
Live Lisa (or Lisa Related) SitesLisa The Painful Guide
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