BRACKENRIDGE%USC-ISIB@sri-unix.UUCP (01/20/84)
From: Billy <BRACKENRIDGE@USC-ISIB> I just got Tall Tree Systems new software for their bank switched memory boards. JRAM is a memory board with built in bank switching. Any 64K segment can be mapped to any 64K boundary in the 20 bit 8086 address space. This allows a machine to use more memory than there is address space. This system allows up to 4Mb memory on a PC. I am using it with 1.25 Mb. Jdrive is a RAM disk emulator that takes advantage of JRAM or any other installed memory to simulate a disk in RAM. There is also JSPOOL, JTYPE, JFORMAT, jetc.... The DOS 2 drivers had never been entirely satisfactory, particularly with XTs. One of the prime attractions of using the JRAM system here was that it was sense switch insensitive. All of our PCs have their sense switches set for the amount of motherboard memory only. This will usually be 64K or 256K depending on model of PC. Earlier versions of the program required the mother board to be fully populated. As we have so many systems all different, we were running into maintenence problems. This latest version of the software is back to the level of maturity that the DOS 1.1 version was. It appears (so far) that you can throw just about any hardware configuration and any switch combination and JDRIVE will sort out the whole mess and make sense of whatever havoc meddling hands have made with the system configuration. Another problem area was preserving the electronic disk over reboot. Tall Tree had supported preservation of the disk over soft reboot (Ctl Alt Del) as long as the simulated disk was entirely on JRAM memory. Now you can have part of the electronic disk on motherboard memory or fixed memory and part on JRAM and the disk will be preserved over reboot. Unfortunately during the reboot process memory had a habit of not getting refreshed as often as one might have wished and parity errors were common. There are now provisions to read memory with parity disabled and write back the value. This can help in saving a file on the electronic disk. Previously in order to enlarge the size of DOS memory at the expense of RAM disk, one had to reboot. Now one can alter the size of DOS memory from a command which can even be included in a batch file. Divide by zero and parity interrupts now are recoverable. Rather than hanging the machine one can: Ignore (not considered wise), Soft reboot, or go back to ROM reboot which may wipe out non JRAM electronic disk. As I have an expansion cabinet and several home brew boards and write flaky programs I am prone to these errors and have run into them already. Recovery has been graceful. The installation process is much simpler. While there are many more options to the driver none are required, and the command syntax is quite simple. A month ago I scrambled my hard disk because one of the programs takes /E as a command to erase the file allocation table. I had mis-typed \ECHO (the name of a directory) as /ECHO and lost my disk. Tall Tree claims to have fixed the problem. Now you must name your directory \ERA to get your disk wiped out by this mistake. I suppose this is progress.