Symbolics machines are not being manufactured from new any more. But there are many in use, and the company is still alive if in a diminished form and under new ownership. The computers are just as useful as when they were built, but computers are fashion items, and clearly this brand of box is not a popular must-have today. That said, Lisp is growing in popularity - perhaps the introduction of the masses to graphics c/o Windows, and object oriented thinking c/o Java, has made what Lisp is about more accessible.
Symbolics machines are made from modular parts, so it is difficult to specify what constitutes a "good" system, to a large extent you can mix and match your specification to taste. Besides it depends upon the use to which it is to be put (and by whom). General guidelines follow:
All Symbolics computers support the Genera operating system and lisp programming environment with sophisticated hardware datatype checking, ephemeral garbage collection and a vast range of such advanced features. When measured in terms of raw CPU cycles, their performance cannot keep up with modern systems such as MCL (from Digitool) running on PowerPC Apple Macs, of CCL (from Clozure) in MacIntel. For example my PowerBook G3 series (a notebook computer) runs basic function calling Lisp roughly 3 times faster than a chunky great workstation like the SGI R4000 under Irix 6.2 running ACL 5.0 lisp, which is itself faster than the fastest Symbolics system at simple lisp function calling. CCL using multi processing (8 core Mac Pro with OpenGL in graphics card) is another league faster - in terms of hardware execution.
That's the bad news. But the reason for getting a Symbolics machine is not to get the fastest elementary Lisp execution speed. The Genera environment is what makes Symbolics machines special, and Genera only runs on Symbolics processors (except Open Genera which runs on Alpha 64 bit workstations (Symbolics are still developing Open Genera, see: Symbolics)).
What a Symbolics machine offers is Lisp and the normal repertoire of computer facilities (keyboard, mouse, ethernet, RAM, internet access, graphics, disk storage, tape, serial interfaces, and on and on) - like any computer, but Genera also provides a fabulous programming environment. It is the tool to have when you need to get your brain round difficult problems, really rich application challenges. The operating system of Genera is written in Lisp, all of which is available to the user, along with the software sources so anything can be investigated, changed, customized. The symbolic debugger and source maintenance tools sets makes coping with bugs possible where conventional systems leave the user hopelessly out of depth (a point worth considering in view of the proportion of R&D time spent writing imperfect code).
[I once sat on a bench waiting for an aeroplane, the man next to me sat slouched with his hands in his pockets, he appeared bright and pleasant but he kept wincing and twisting his face into contortions. When his gaze connected with my eyes, he flashed a brief and reassuring smile, before returning to his mental genuflections. After some time, I asked if I could help, he laughed and explained that he was a surgeon and was practicing tying knots inside a matchbox inside his pocket - practice for when his fingers are in confined spaces inside a patient. From a Genera point of view, the conventional data oriented code mechanics seem to suffer from this problem, though they also spend much effort in avoiding tackling difficult problems in the first place]
Symbolics systems were way before their time (and Genera probably still is today), a crime which punished the company's commercial success. So Symbolics computers are not fashionable today. That's the bad news, the good news it they can be picked up second hand very cheaply. What used to cost $100,000 a few years ago can be procured for a thousandth of that sum today.
Enough propaganda ... let's move on to what Symbolics computer to get? In as much as they all run Genera, users interested in exploring Lisp, developing applications and expanding their minds in general, will find any machine satisfactory. The choices revolve around getting a system which fits the environment in which you are working (space is not always generous at home, or budget for power) and which can be maintained (the simpler the system, the less there is to go wrong). And of course finding one in the first place.
Symbolics machines are built ruggedly, they are exceptionally reliable, but like any such device they can fail. In my experience the order of failure likelihood is: monitor (usually remedied by internal adjustments, or any competent monitor repairshop) the disk (as reliable as any disk), then PCBs (often remedied by reseating chips which have thermally crept). Obviously if the machines are treated gently they will prove more reliable than if they are bashed about and left damp and dirty. By and large, a used system is more reliable and better value than a new system.
Large L machines (3600, 3670 and 3675) need space and take serious shipping (the tallest, the 3600, is chin height), they are interesting as the earliest pioneers of commercial Lisp Machines - I hope to find a museum to give mine a good home. The 3640 is more compact, but takes two people to lift comfortably.
The G-machines are probably the best compromise of 36 bit computers. The 3610 and 3620 are small enough to be lifted easily and do a good job, but lack the expansion options of their bigger brothers. The 3630 has space to support color hardware (such as the CAD Buffer II). The 3650 is the big brother of the G-machines and has capacity to support S-Animation graphics. All G-machines use the same CPU.
It may be worth pointing out that Symbolics users are roughly divided into those interested in Lisp and applications development, versus those interested in 3D animation graphics for film production (a la Hollywood). The machines are the same, the graphics specialists just pile in the maximum exotic graphics hardware and animation software (and often have little idea that Lisp is running inside).
The latest machines are based on the VLSI Ivory processor, this 48 bit system is the fastest and most compact. This allows it to be packaged as a conventional standalone computer (the XL 400 and 1200) and as a coprocessor for Sun (UX) and Apple Mac (MacIvory I, II & III) computers. The NPX is a network only system interfaced via X-windows.
My sense of value for these systems is that an entry level 3640 or 3620 is worth a few hundred dollars sight unseen, working or not. Which for a user who needs an extra system or spares, makes superb value. But if a system needs building to order, servicing, setting up etc. then obviously a considerable amount of time can be required which at the lowest time charge rate will be more than the cost of the whole system.
A high spec XL1200 with Vector accelerator, loads of fast disk, RAM, FrameThrower, Exabyte tape streamer, Frame Grabber, ... the works, is equivalent to a high end SGI system, the sort you'd run Nichimen graphics systems on. I think that if you can get one for $10,000, then you have a bargain.
For a reasonable spec 3630, with color, in good running order I'd aim for $1000, all in, the complete hardware and software package. The price of a word processor, but a big league workstation.
I think that the way to get your own Symbolics computer is to identify what you want first, then make a clear cash offer to someone who owns one. This in preference to adopting a retail customer attitude. Remember that the cost of shipping can be more that the item cost.
For documentation, use the online Document Examiner (DocEx) in preference to the 1/2 ton of trees which it takes to produce a paper copy of the same material which in paper form looses its sophisticated search and hyper-text interactivity. You can always print it out if your must have it in your hands.
To both keep your system operational and to get help with it, use the W3 and phone. The first port of call is the SLUG (Symbolics Users Group) list (slug-request at ai.sri.com), but most activity is between individuals (rather than broadcast). I believe that Kalman Reti is the primary contact at Symbolics itself (reti at wilson.ai.mit.edu). Another goldmine of Symbolics gurus is via the community of CL-HTTP users (www-cl-request at ai.mit.edu), though I am sure the group would not welcome traffic blatantly centered on Symbolics rather than CL-HTTP.
More bad news: the companies Franz and Harlequin sell Lisp implementations for PC and Unix computers. Well that's not the bad news, the bad news is that there lingers in some of the staff of those companies a legacy of illwill towards anything to do with Symbolics (I presume memories from when Symbolics was commercially world caliber and made their offerings look naive). But the good news is that there are many more employees in these companies who are supportive and indeed very experienced. Also, should you be a newcomer to Lisp through your Symbolics system and you luck upon an invention, then you can expect to be able to port your Common Lisp and CLIM designs painlessly to run on stock hardware c/o these software-only Lisps (though at a price). Creating fresh, sophisticated and pioneering designs is probably the most tangible, if uncredited, output of Symbolics users - that is not to say that these designs have been finally delivered on the same platform.
Like everyone outside the US, I was grossly overcharged by Symbolics UK (some $40,000 per annum in maintenance charges alone). The frustration and cost of such a situation drove me to buy spare systems in order, with great trepidation, to be able to provide my own maintenance. I need not have worried, the task was simple, anyone can do it. Now I want to thin the inventory that I am not using - that's by way of an explanation for my offering some of my Symbolics kit, though I'm in no hurry. If interested, get in touch, make me an offer (money or barter).