I would call that like ... a frustratingly nice score, LOL. Lots of Symbolics equipment saved which is a huge plus, but if it were me, I'd rather have one Ivory machine that ran, versus a whole pallet of 3620s and 3640s with bad drives ... it'll be interesting to see if he's ever able to get one of them up and running. Funny he does not recognize the famous VSXXX-AA! One of the best mice ever made, IMO :O Best, Sean On Fri, Sep 25, 2015 at 10:44 AM, Guy Sotomayor <ggs at shiresoft.com> wrote:

On Fri, Sep 25, 2015 at 7:44 AM, Guy Sotomayor <ggs at shiresoft.com> wrote: A colleague of mine and I tested David Gesswein's MFM emulator ( http://www.pdp8.net/mfm/mfm.shtml) in his 3620; it was able to capture a disk image from the 3620's MFM disk and successfully boot Genera from the image. So there is a solution, at least if you happen to have a system using MFM disks. (And an image or working disk to start from...) Now, an ESDI emulator... that would be nice to have :). - Josh

On 09/25/2015 07:44 AM, Guy Sotomayor wrote: ...so how fast will one of those run FORTRAN? (Ducking and running for cover...) Chuck

On 9/25/15 11:23 AM, Chuck Guzis wrote: as fast as their owners needed to.

Boot strapping a machine isn't impossible. It may be difficult but not impossible. I boot strapped a IMSAI with a "DigitalSystems" disk drive and controller. I'll admit I did know 8080 code but I had to start from scratch on the disk controller. No nice little WD controller chip to start with, just a 12X12 board to TTL. I didn't even know it was a DMA device when I started. I've trouble shot a 20 bit mini with no schematics. A lisp machine would clearly be difficult but not impossible for a determined hacker. If it was designed to run it can be made to run again. Dwight

I don't know you and you obviously don't know me. I know many people like you. Many that claim to know what they are doing and are experts in there fields. I am curious about you statement" It wasn't", as to designed to run. Dwight

I get no credit for repairing a 20 bit computer without schematic. Not 36 bit but still of some worth. The disk controller on the imsai was a bit controlled state machine. Not 36 bit but not a trivial toy repair either. I think you don't know me. Dwight Dwight

On 9/25/15 9:20 PM, Guy Sotomayor wrote: It's good to see that the MFM emulator worked on a 3640. I bought one and planned to try that experiment at some point. The SCSI emulator (scsi2sd) works well on the scsi based xl1200's and I have cloned a few disks. I have a working 3640 with a booting MFM disk which I should/will clone once I find the pcb (which is currently hiding) It's true about the disks - the bad block info - at least on the large SMD and RLL lists was written at the factory once and that was it. But if you had a "perfect disk" (for example one that was emulated), you could recreate a FEP file structure from scratch and if you had a distribution tape you should be able to load the needed files onto it. I suspect you could do all of that "outboard", i.e. using a linux computer into a disk image. The FEP file structure and LMFS file system are not that complex. And if you could take a MFM signal image and turn it back into 1280 byte blocks, then you'd have a good example to decompose and compare with (since that now exits). Heck, worst case you could do it from the FEP itself - but I think you'd need a dc-300 drive emulator and a image of a distribution tape. That should not be hard - the carts exists and I can't imagine a tape interface being that hard to emulate. I think the MFM format, even with it's odd block size is known and reasonable; But the FEP loading code is obscure. (I've never seen FEP source code despite searching for a long time) But the format of the disk is pretty well documented in the lisp code and is known. I made a feeble attempt at a 3600 macro code interpreter at one point. More just for fun than anything else. I based it on the microcode in the patent application but it only got so far. I think documentation did exist, but I'm not sure it's ever seen the light of day. I've never seen any. The holy grail would be a source copy of the latest microcode with all the support files. It has to be on a magtape somewhere in someone's basement... There is documentation for later ivory based machines (xl1200, etc...); the macro code and other important information has surfaced and is available. The emulator has gone through various incarnations and improvements but remains (sadly) private. I heard the latest version was completely rewritten in modern C. I still hope some day someone will cough up some tapes with internal files on the 3600. It should be possible to make an emulator or at the very least run the microcode. There are schematics on the web. I have (briefly) considered putting them in an FPGA but fortunately came to my senses. I think if I had the FEP source code I'd get motivated again because I've yet to figure out the format of the microcode binaries (which would be essential if one wanted to actually run the 3600 hardware engine in simulation). It might be one of those "be careful what you wish for" statements :-) I still remember Al sending me the binary images of the CADR boot proms. I think that 3620 is VLSI based. There have to CAD files somewhere which describe the logic. -brad