Mr. Frank Davis
Editor UPDATE!
513 E. Main St.
Peru, IN 46970
7/10/92
Dear Frank,
I’m pooped! After many hours at the keyboard, and swearing at myself for clumsy goofs, the “fabled” TIMEX BEU has its start in the ROM BYPASS BOARD. This board will do the job but requires bringing the ROMCS signal out to A5. Later, I want to revise it to work without touching a screw. Time forces me to compromise.
Board “A” is an extender except for BE signal interruption. It hosts two dedicated circuit boards.
Board “B” carries the bypass memory in the form of battery backed static RAM. This includes 32k of EXROM, though another 32k is available as volatile memory to make a total of 64k! I have the code patches necessary to let the 2068 recognize this extra available memory.
Board “C” is the Expansion Bus Driver. Though a TIMEX type bus is a little simpler, going to the IBM AT bus is more practical because of the many bargain devices available for it. Some may point out that the bus frequency is different, not knowing that bus frequency variants already exist with no trouble. Some may argue that some signals are incorrectly used, forgetting that those signals address a motherboard that isn’t there!
Reminiscing is nice. Remember Computer Trader Magazine? Here is a 3-d logo I did for him. Notice the tricky way that only the “T” is opaque. I have a graphics wire-frame program that lets you display anything you want in these windows. Its default is the three great pyramids of Egypt with Carmen Sandiego having stolen the SPHYNX. Only a flat runway remains.
I need working boards to repair the TIMEX system to what it was. Only then will it be possible to use the crippled DOS commands as intended. I think John Oliger will jump at the chance to relocate his system into EXROM, where no illegal commands are needed to access it. All that nice buffer space could make his mouth water. There should be some constraints, however, so that future improvements are not blockaded. One of these is letting the system grow directory trees. Another is to provide 16 bit FAT table entries while keeping the ability to read disks of any format. Then, a hard disk will have the same parameters as most floppies. Command syntax would be identical.
The disks (IBM 360k) are .PCX files for the job. I cropped and sized four 1x etching masks so you can print them out on your ink-jet at 360 dots per inch using transparencies. The 2x paper masters included are 180 dpi.
In Dayton, if I’m lucky, I could demonstrate booting SPECTRUM into the 2068 on demand, and back out — maybe a bit more than that if I get my new EXROM code debugged.
ZZZzzzz…..
