McGuffey@DOCKMASTER.ARPA ("MAJ DAVID C. MCGUFFEY") (04/20/88)
Sorry about that, I wasn't thinking--I do so much via the net nowdays. Extended and expanded memory systems take advantage of the gap between the top of the 640 kb system memory and the video memory on the IBM-PC architectures. I think there is a 128 kb gap, which is used by a driver to swap pages from the extended/expanded boards into the gap. Zenith however, did not follow this architecture and allowed the main memory to go right up to the start of the first video memory plane. As far as I know, there is no way to get extended/expanded memory to work in the same manner. Although I have heard that there is a program here on the net called RAMLIM that allows a similar function to occur at a gap between the top of the three Z-100 video planes and the start of ROM. I've never seen a program written for the Z-100 which would take advantage of anything more than 768 kb, so even if the capability existed, I don't know what you would use it for. The approach I took was to fill up the Z-100 with a full 768 kb and then add the 768 bk RAMDISK. Interestingly enough, the FBE approach is similar in function to the extended/expanded systems on the PC. They do a similar swapping function with the block of memory between 512 and 768 kb. The first 512 sits on the motherboard (you take the top 9 chips off the motherboard and place them in bank 0 of the modified Z-205 card), and the new PAL allows the system to find the first 512 kb on the motherboard and the last 256 kb on the card. When one access main memory, one sees a contiguous block from 0 to 768 bk, but when one access the RAMDRIVE, the 256 kb blocks (3 ea.) are mapped into the top 256 kb block of system memory--the same process as expanded/extended memory on the PC. It is a neat system, smooth installation, and I've never had a problem with memory management or crashes (even with PERKS and other TSRs installed) at 4 or 8 mhz. I did run into a memory management problem at 8 mhz when I tried to install two cards though. If you are at 8 mhz, I would recommend only running one card. If you chose to get one of these cards, it will come with the switches all preset and the drivers and source and manuals from FBE. Essentially what you get is the FBE kit with all of the work already done, 27 ea 256 kb chips (fast enough for 8 mhz) already installed, and fully tested. All you need to do is take apart your Z-100, remove 9 of the 256 kb ram chips from the top bank on the mother board, place them on the card, install the PAL and the card, go through the tests noted in the manaul, and install the driver in config.sys. It's all in the manual, but you can skip all of the pages about soldering a wire which connects all of the 1 pins together. As before (with the Z-217 and Z-216-8), if it arrives unserviceable or won't run with your particular ram upgrade and speed kit, send it back to me--sooner or later I'll find someone who can use it for salvage or make it work in their hardware configuration. Incidently, the guy who runs FBE was very helpful in putting together a special PAL and told me where to modify the driver for the second board--I'm sure that if you gave him your motherboard serial number, make and model of ram upgrade, and speed kit, he would take care of the rest. Super outfit! If you are interested, I'll set it aside along with the Z-217 and Z-216-8 cards and assorted hardware/manuals. I'm looking for $150.00 for each card, and because of the high cost of the original Z-205, the value of the 27 ram chips on it, and my own money and time invested in the upgrade, I can't reasonably go any lower. (I was already pushing my wife's limits by going and buying a H-386--you may know the feeling). Dave McGuffey PS. My home phone no. is (301)-498-1466, and work is (202)-693-1612 and (301)-859-4533 (poor alternate, as I spend most of my time as a liaison between the NCSC and the Pentagon--the 202 area code).