Brasstacks

I've been playing around with the MacIvory FEP (Front-End Processor) to learn more about how the Symbolics Ivory environment gets started. Not everything is yet clear to me, but I wanted to record some information about the "cold load" environments files. The Ivory chip uses 40-bit words, where 32 bits make up the "address" or immediate portion of the word and the upper 8 bits are a combination of type tagging and "cdr code" flags which allow for compact representation of lists and, in code, program counter sequencing flags to allow for half-word instructions to be compacted around full-word instructions in the stream. A lot more information can be learned from a number of sources. The previous generation "3600" machine was disclosed pretty widely in the literature, and ideas like type-tagging and cdr-coding are very similar between the machines. Bitsavers has a few files scanned from internal documentation. Most informative are I-Machine Ar...

The previous notes don't seem to work in all circumstances. In particular, trying to enable a CHAOS networking port in .VLM configuration causes NFS to fail in the writing of the Site file. I have been unable to diagnose this as it appears the VLM stops trying to use NFS to access the file after starting a write, and then times out, not even showing any activity on tcpdump when a restart is attempted. It's possible the presence of a CHAOS interface causes it to expect NFILE or perhaps it decides to prefer FTP over TCP. In principle, it should be possible to invoke the debugger on the VLM to understand what is going on, but all the networking is very flexible and elaborate and I have no idea how to debug Genera at this point. On the Linux side, I can find nothing at all that shows an error or misconfiguration or anything at all once the problem starts. After defining the site and saving an incremental world, adding a CHAOS interface seems OK, but I have been stumped trying to ge...

A quick note to try to make this information available on the net. Trying to troubleshoot my Symbolics MacIvory, where my Quadra 900 was encountering bus errors from time-to-time and, at least once, Genera spammed me with tens of thousands of notifications about low-level drawing operations gone bad, I wanted to exercise the NuBus memory card (a National Semiconductor NS 8/16 with only 8 MB of RAM). The FEP ("Front End Processor") contains a memory test routine, but it has to be explicitly loaded. FEP Command:  is the prompt that shows you are talking to the "MacIvory FEP"; in the "Ivory" menu of the Genera application, you should be able to "Transfer to the FEP". The FEP prompt responds to the "help" key, by the way, and has commands like " Show Command Tree"  that shows the loaded commands. FEP commands themselves are stored in .FLOD  files . Show Directory FEP0:>*.FLOD.newest will list them. " I328- ...

Working with ResEdit and DeRez, I believe I have traced out the keyboard protocol used by the MacIvory ADB adapter . My adapter is on the blink, probably because of the small screw I found rattling about inside. I hope DKS can bring it back to life, or the PIC-based project I had begun will make its way back to the front burner.

The ADB adapter has not just given me some help uncovering the behavior of the Rev. C Symbolics keyboard protocol, but also works when attached to my MacIvory. Along the way (and with the help of David K. Schmidt) I encountered some glitches, mostly stemming from my original accidental trashing of the System file DKS installed. There are a few software components the ADB adapter box needs to convert the Symbolics keyboard to something the Mac OS 7.6.1 (including the "FEP" window which communicates to the Ivory board on a low level) will accept as a keyboard with the right keymapping, and furthermore to something the Genera application will recognize with all the Symbolics-specific keys. Without these components, you will see one of the following two stages of malfunction. Stage 1: The mouse connected to the ADB adapter works fine. In the Mac OS (including the FEP window), there is total keyboard confusion, with the keys all scrambled. On the Genera side, things are less ...