80-Bus News


July–August 1984, Volume 3, Issue 4

Page 18 of 43


There are other ways to do it, but the above code works on both of my Nascoms, and CP/M, CCPZ etc, boot up and run with either GM862 or GM802 RAM boards installed. Having got thus far, there was still the job of configuring CP/M to actually drive the other memory page/s as RAMDISK. If Gemini’s CONFIG.COM is available for the version of CP/M used, then it’s a doddle. One simply selects Menu option 8 (7 on some versions) and if you are using the GM862, have SIMON in EPROM at F000h, and run 60K CP/M or whatever, enter 3 for the number of extra pages and 60 for the Kilobyte size of each page. By selecting the appropriate number of pages, CONFIG can accommodate up to three additional 64K GM802 boards in the same manner, but do NOT specify more boards or pages of RAM than are installed because the system will crash and/or fail to boot. Test the system by typing M: to select the RAMDISK, when the M> or M0> prompt should appear. A DIR command should respond with a NO FILE message. Return to ‘normal’ via an A: command and type STAT M: when the response should indicate between 172K and 178K ‘bytes free’ if three 60K pages are in use. If only one 60K page is in use the response will be a (disappointing) 52K to 58K depending upon the size of the BIOS and the allocated RAMDISK Directory. Try PIPing and STATing programs around between Disk and RAM to ensure that all is well. SWEEP may also be used, but the versions written in high level code hang-up if zero sized files are transmitted and exhibit a few other minor bugs. However NSWEEP 2.07, a later Z80 code version, has behaved faultlessly with RAMDISKs. The proven configuration on the Disk system tracks may now be SYSGENed onto other disks or the configuration process can be repeated as required.


To activate Page mode RAMDISK operation under later versions of SYS requires that module SYSB1 be re-assembled using M80 with the appropriate software switches set as follows:–

Page 18 of 43