Project Log 2 - What?? Why?? How?? Huh??

A project log for A Brand New Apple Lisa

Producing a Functional Clone of the Apple Lisa 2/5, using NOS components.

dosfoxDosFox 08/05/2023 at 23:310 Comments


So... what have I managed to achieve here?

Let's begin with a quick bit of history. 

As most people are aware, the Macintosh has been a series of computers that Apple has been selling since 1984 through to today. Originally, these had a really cute design - a small beige box, with a built in 9" Black and White CRT, with a solitary floppy drive as your only boot medium, running one of (but not the first by any stretch of the imagination) Graphical User Interfaces available to the public. 

Inevitably progressed marched on, and features were added or evolved into the final flat slab of an iMac that we have today - obviously with some families of Macintosh deviating and evolving on their own, to create some fascinating examples such as the G4 cube, Xserves, 2013 "trash can" Mac Pro - including the ill fated and frankly weird Twentieth Anniversary Mac. 

But what exactly came before? 

Somewhere after the Apple ii (a series of cute 8 bit computers with a single logic board built into a keyboard) and before the Macintosh - whilst completely ignoring the Apple iii, because that was its own strange kettle of fish that was taking place at the same time - there was the Lisa.

The Lisa itself is similar in form factor to the Macintosh, with a similar concept. It used the same 680000 processor, integrated floppy drives, with a 12" Black and White CRT, running a very early Graphical User Interface (still not the first, as that was developed by Xerox, despite what some die hard apple fans will tell you). However, the Lisa is a very different beast to the Macintosh. 

As you may of noticed, our expensive Fruit based computer of choice is the Apple Mac instead of the Apple Lisa. You may also of figured that the reason for this, is because the Lisa was a bit of an absolute flop. So much so that quite a few of the stock ended up in a landfill.

Mainly due to the high initial cost - it launched at retail for $9,995 in 1983, whilst the Mac launched at $2,495 in 1984 - brought on by the sheer complexity of the Lisa. 

The "core" of the Lisa consists of four main boards. The CPU board which handles the CPU, ROMs, MMU (!), and the video generation. The IO Board handles the main peripherals like the floppy drive, keyboard, mouse, soft power, hard drive interface - all driven by a literal 6502, just to handle the peripherals. The ram boards (usually two for a total of 1mb) consists of at least 72 individual RAM ICs for 512k of RAM Plus Parity. Whilst the motherboard was a simple-ish backplane consisting of the card edge connectors and the connectors. 

Compare this to the single logic board of the Macintosh, and you start to see the over engineering that went into the Lisa. 

Despite being somewhat of a flop - Apple still managed to produce three distinct variants of the Lisa. The Lisa 1, Lisa 2/5 and the Lisa 2/10. 

The Lisa 1

The hardware of the Lisa remained more or less similar throughout its production, however, the Lisa 1 is the most distinctive of the three - as it contains two 5.25 Fileware drives, that were also referred to as the "Twiggy" drives. 

These disks held a fairly impressive for the time 851kb of data each, and were developed for the Lisa as well as Apple iii. In fact, some of the early Macintosh Prototypes that were given to developers used Twiggy drives as well!

The Lisa 1 is also able to use an external 5mb hard drive known as the "Profile", that was able to connect to the Lisa via the external parallel port connection. 

The Lisa 2/5

Unfortunately, the Twiggy drives were notoriously unreliable. As such, the following iteration of the Lisa - the Lisa 2/5 - used the exact same 3.5" Sony drive that was being developed for use on the Macintosh 128K. 

Realistically, the use of the 400K drive instead of the Twiggy drives was the only major hardware change from the Lisa 1 to the Lisa 2/5. The core four boards remained effectively the same, except for updated ROMs to use this new 400K drive. 

The only added part of hardware to get the Sony 400K drives to work in the Lisa was an adapter called the "Lisa LITE" - which simply adapter the 24 way Twiggy connector to the 20 way Sony connector, whilst also generating a PWM signal for the rotational speed of the floppy drive. 

Therefore, to upgrade a Lisa 1 to a Lisa 2/5, you just needed to swap a ROM, remove the old twiggy drives, add a new adapter and the floppy drive, then put a new face plate on the front, and then you were done. In fact, this is the fate of a fair few Lisa 1s, they were upgraded officially by Apple to a Lisa 2.

This is a practise that Apple had done before when upgrading Apple iis to Apple ii+s, as well as later on when Apple offered to upgrade existing Macintosh 128Ks and 512Ks to Macintosh Plusses. 

An interesting detail to note is that the "5" to note in Lisa 2/5 does not refer to the RAM available in the system, but more interestingly to the capacity of the hard drive - specifically the 5mb Profile!

Something else to consider as a collector, is that if the Lisa is a 2/5 or a Lisa 1, is that the IO board contains one hell of a battery bomb - it's more akin to a battery Hydrogen bomb. It is literally Four AA Batteries Strapped To The Bottom Right Of The IO Board. When these go off, they can take out the IO board, the motherboard, and in some rare cases the CPU and RAM boards. Be careful and don't forget TO TAKE THE DAMN BATTERIES OUT.

The Lisa 2/10

The final iteration of the Lisa 2/10 was the only version of the Lisa hardware that resulted in some redesigns of some of the PCBAs. 

The main difference between the preceding Lisa 2/5 and the Lisa 2/10 is that both the floppy drive and the hard drive were upgraded. The floppy drive was upgraded to an 800K double sided drive, that does not use the PWM pin - meaning no Lisa LITE is required. The external 5mb hard drive was upgraded to a 10mb internal hard drive known as the "widget", hence the name 2/10.

As such, the presence of the widget, and the removal of the Twiggy drive interface, resulted in the motherboard being slightly redesigned. The external parallel port was rerouted internally, and the connector for the floppy drive was reworked. There was also an interrupt key added to the rear of the system. Additionally, the Lisa 2/10 IO board is prized by collectors for one key feature - the batteries were removed. As such, a Lisa 2/10 does not have the same battery leakage issues as the Lisa 2/5. 

The IO board, potentially just as a cost saving, does also contain a new custom IC. This is the IWM or "Integrated Woz Machine", which is used to control the floppy drive. This IC was first used - as far as I can tell - on the Macintosh, and effectively combined the functions of the Apple ii floppy controller into a single IC, with some extra status registers. 

It must also be noted that the IWM was not added just because the 800K drive was being used, as a Lisa 2/5 (with the right ROM) can drive an 800K floppy drive just fine with its Apple ii inspired floppy controller. 

As such, a 2/10 can be identified either by the missing parallel port on the back, or the presence of the IWM on the top left of the IO board. It can also be identified by the fact that the batteries have not left the system a corroded husk of plastic and sadness.

The Lisa 2/10 - as you can probably tell by its increasingly Mac-Like technology - was also released by Apple as the Macintosh XL. It was the first Macintosh with an impressive 1mb of RAM and internal 10mb hard drive back in 1985. This was possible, as there was a software shim that effectively loaded the 64K ROMs found in the Macintosh 128K and 512K into RAM known as MacWorks. Aside from the inclusion of MacWorks (and potentially the "square pixel mod" that was a trio of ROMs and a cable harness for the CRT, that turned the rectangular pixels on the Lisa, well, square), the Macintosh XL is fundamentally identical to the Macintosh 2/10.

So what did I manage to build?

Quite simply, the machine I have replicated is effectively a Macintosh 2/5, this is due to two main reasons. 

The first, is that although I would love to build a Lisa 1 -  unfortunately, the Sony 400K and 800K drives are much more available than the original Twiggy drives. There is someone who is in the process of making replicas of the Twiggy drives, but they will undoubtedly go for more than what I can afford.

Additionally, the Fileware disks themselves are not standard 5.25" disks, and original Fileware disks can go for over £100, not to mention shipping. 

There is also the simple problem of not owning any other Twiggy capable machines - so I would have no way of even booting the Machine if I did somehow find some Twiggy drives. 

The second major reason is that the Lisa 2/10 contains the IWM, which is a custom Apple part. It is important to know that within the Apple Lisa 2/5, there are only two Apple custom parts, both of which can be replaced easily. You can build an Apple Lisa from scratch. 

There is some inspiration from the 2/10 within this new Apple Lisa though - there are no batteries within the IO board, as I did not want to run the risk of finding a battery explosion many years later. Additionally, to avoid building a Lisa LITE, a specific ROM from Sun Remarketing (I'll get to them later) was used to allow for 800K drives to be used in this system.

How was I able to build an Apple Lisa?

Strangely enough, how I was able to build the Lisa is directly tied to the fact that the Lisa has an incredibly leaky battery. 

The CPU board, IO board, Motherboard and Power Supply were already reverse engineered and proven to work by two frankly incredible people - Alex and Warmech. 

Somehow, at roughly the same time, we had all had the same idea to reverse engineer boards for the Lisa. Whilst work and life (and lets be honest, my atrocious mental health) got in the way for me, both of these incredible people were able to design the schematics in CAD, send off the boards for manufacture, build them, and THEN even complete a few design iterations before I even got around to starting the schematic. Hats off to both of them, this project probably would never of been able to get done without them.

(seriously you should of seen my face when I announced on social media I was planning on building a Lisa from scratch, only to be told that two people have already done 90% of the design work for me).

Alex was able to produce brand new designs for the IO board and the Motherboard from schematics (see their work here), whilst Warmech produced a new CPU board and PSU (see here).

As such, all I had to do was:

  1. Work around the two custom parts - these being the main system oscillator that has a very specific frequency, and the COP Microcontroller on the IO board (it used an internal Mask ROM instead of an external ROM, so it is technically the only truly Apple specific part on the board)
  2. Figure out how to program the two 256 byte Programmable ROMs (Not EPROMs, PROMs!) that are used in the Video generator circuit and the floppy controller circuit as finite state machines.
  3. Build the CPU board, IO board, PSU and Motherboard. Whilst sourcing the slightly hard to find NOS components
  4. Purchase an original Apple RAM board (the only original part here) and repair it using the Apple Lisa Service mode. Then repair it again after someone tried to kill it. 
  5. Build a cable harness with a speaker to go from the Power Supply to the Motherboard.
  6. Build an interface for the keyboard, power button and floppy connector. Also get a keyboard inteface
  7. Make sure that I have a monitor that can actually sync to the weird Apple Lisa video frequency. Also make sure that my M0110A keyboard and M0100 mouse still work.
  8. Debug the entire thing to figure out why it's not working. Three times over.
  9. Try not to set fire to my house
  10. Keep my sanity whilst doing this 

Okay, maybe I did a fair bit of work. 

In the next post I'll be explaining precisely *why* I built a Lisa clone, as well as the few workarounds that were needed to make sure that this Lisa can be build from scratch.