REPRINT FROM SYNC LINK
Our last newsletter carried an article by Greg Lloyd, describing a RAMdisk unit that he had recently obtained from Larken Electronics. I have recently purchased one of these units, and should like to tell something of my programming experiences with it.
Firstly, when I got it I could not figure out how to use it effectively. After all, while it can contain a total of 256K memory, mine only came equipped with 64K and there really is a limit as to how many program one can hold with that. Which programs should I place on it, etc?
On top of that I already had a second drive on my system that seemed to be only used when I wanted to copy a program. Of what use was another bit of expensive memory. And it is expensive, if compared to the memory capacity of a disk. A disk will hold 360K and costs about 65 cents. A 32K SRAM chip costs about $15. And the RAMdisk is really a solid-state drive, not a memory expansion to your computer. That is to say, you still have only 38K of memory in your computer to play with. The RAMdisk memory is not bankswitched in to the computer; it it loaded into the computer memory the same as from a conventional drive.
However, despite this unpromising prospect I have found a very fascinating application. What I have done is to place 58 of my most useful utility files on a single disk (I call it my OMNIBUS disk), and installed it in my second drive.
I then placed the several menus (the menu program listing in the Nov/Dec ’87 issue of this newsletter) required to access these files into the RAMdisk. In the beginning I had one AUTOSTART (menu) program, and several other menu programs i.e. menu.B1, menu.B2, etc.,that I called up from that AUTOSTART menu. I found that presently I had used 7 of the 12 available tracks on my RAMdisk; horribly extravagant. (The RAMdisk uses the same tracks format of the other drives)
It was then suggested to me that I combine several menus into one program. This made sense, because as it was I was storing a program of about 1500 bytes onto a 5090-byte track. The other bytes, 3410 of them, were lost. I started combining menus onto a single program, and now I have 5 menu screens combined. More will follow. I use a menu option to move to the various menus.
Most of the programs themselves are on the OMNIBUS disk, installed more or less permanently in the second drive, and are called up from the menus obtained from the RAMdisk. Where a program is called up that resides on other than the OMNIBUS disk, the menu displays a request onscreen for that disk to be placed into the first drive, PAUSE’s until you indicate ‘ready’ by a keypress, then loads from that drive.
Larry Kenny has revised his DOS EPROM, giving a new command which has proved very useful in this application. The format of this command is PRINT USR 100: NEW (or PRINT #4: NEW). This provides a ‘warm’ AUTOSTART capability to the DOS.
I use it this way. I have modified many of my programs to provide an exit from the program. The exit normally would take you to a STOP command. To use this new DOS command I terminate a program to the following line sequence.
LINE 9000 PRINT #4: GOTO 4: PRINT #4: NEWThe ‘GOTO 4’ points the DOS toward the RAMdisk and the ‘NEW’ initiates an AUTOSTART routine in the RAMdisk to bring up the ‘menu’ program. The effect is to bring up the OMNIBUS disk menu at any time from within a program with a single keystroke. Note that this new command is for all drives; it’s use is not confined to the RAMdisk.
This new DOS command also offers another interesting programming possibility. Invoking the ‘PRINT #4: NEW’ command will bring up an AUTOSTART program in the drive to which it is pointed. It does this without shutting down the computer. Thus, any M/C program presently in the computer (so long as it is not overwritten by the AUTOSTART program) remains in place awaiting use.
Larry advises that this command is in Version 2 of his DOS EPROM. Before you all rush out and ask him for it, I suggest that you wait until he has had a chance to incorporate some other features into the DOS, that he speaks of doing. Improvements to the printer driver, and changes to the NMI routine, I have heard; among others.
Now, I could hardly recommend that everyone go out buy one of these RAMdisks. But what I have found is that for those persons with two drives it certianly maximises the use of the second drive. And it most assuredly reduces the number of keystrokes required to operate the Larken system, plus reducing the number of drive startups by possibly a half. And of course it is silent and speedy, when compared to a regular drive!