Msg: 6292 *Conference*
02-07-96 22:54:01
From: RICHARD HANSON
To : ARTHUR TYDE
Subj: REPLY TO MSG #6291 (EXPANDING THE MODEL 102)
Thank you, Arthur. Your kudo's are greatly appreciated. Addressing your XR4 adn URII co-existance question: The XR4 is installed in the option ROM socket. It may be configured as any combination of 4 RAM, or 4 ROM, or 2 of each or 1 of one and 3 of the other. An XR4 RAM sub-division is used as swap-areas with the internal RAM. It "looks" and "acts" as if you are switching banks of RAM but you are actually swapping, byte-for-byte, between the RAM sub-division in the XR4 and the RAM of the Model "T". An XR4 ROM sub-division acts just like an option ROM, i.e. the option ROM code runs from within the address space on the XR4 as if it was an option ROM. The XR4 programming does all these tricks and more. Installing an existing option ROM "on" the XR4 is straight forward once you understand that an ROM is "kind of" similar to a diskette as a storage device in that the code (program) is a file stored on a medium. However, unlike a "true" storage medium, wherein the "code" must be "copied" to RAM and excuted there, the ROM-based code "runs" from where it's stored, i.e. the address spaces it occupies on the ROM. Let's hope you're still with me... You start by installing the option ROM into the Model "T". Then, you run one of the XR4 programs that will make a copy of the option ROM image onto a diskette, i.e. tpdd, tpdd2, DOS disk via a null-modem cable and terminal program. Note: You would do this for each option ROM you own. You would end up with each of your option ROMs images as a separate file in a diskette. Next: You remove the option ROM and set it asside, then install the XR4 and set it up for as many ROM sub-divisions you desire, 1, 2, 3 or all 4. Lastly, you use one of the other XR4 utilities to copy each option ROM image into a separate sub-division of your XR4. You are finished. From then on, you simply use the XR4 OS (operating system) to swap RAM images and move the pointer to whatever ROM image you choose to use with that RAM. Again, remember, the RAM in use is always the Model "T"s RAM ... not the XR4's RAM ... you might think of those as 32K file drawers. I trust this is as clear as transparent mud?! (grin) ...now there's an image!