hansen@brand.usc.edu (Richard Hansen) (03/16/88)
I recently installed the FBE 256K memory expansion in my old motherboard style Z100. I previously had a 256K Zenith Z205 card for a total of 488K. Now, how does one use the 768K main board memory + the 256K S-100 memory? Can it be done. I tried to treat the 256K as extended memory (like an IBM AT), but that didn't seem to work. I know MS-DOS limits me to using only 640K with the remaining 128K (of the main board 768K) available for VDISK or other ramdriver. I am currently configured with a 256K VDISK and 512K for MS-DOS. Any help or suggestions would be appreciated. If using the 256K card is now impossible--is anyone interested in buying one slightly used but fully functional Z205 S-100 256K Memory Expansion board. Richard Hansen, University of Southern California ARPA:hansen%brand.usc.edu@oberon.usc.edu UUCP:...SDCRDCF!usc-oberon!brand!hansen
eboyd@APG-1.ARPA (Earnie Boyd AMSTE-TEF 3077) (03/19/88)
First, MSDOS does not limit you to 640K. That's a PC-DOS limitation. The Z100 and some others Kaypro I think are able to address and use 768K of RAM. FBE Research Company, Inc, 11648 Military Road South Seattle, WA 98168 (206) 246-9815 Sells a kit ,ZRAM-205, for $49 to modify the 205 card for an additional 768K of RAM-Drive. 256k chips are extra, 27 are required if you have 768K on the mother board - chips are kinda high right now!
GUBBINS@RADC-TOPS20.ARPA (Gern) (03/20/88)
It is a Vicious LIE that MS-DOS can only access 640K. No! No! NO! MS-DOS can access at least 1MByte (maybe higher?). The architecture of the machine sets the upper limit. IBM-PCs set that limit IN HARDWARE to 640K, some clones (Z-150 is one) can be altered to let MS-DOS access 704K unless you have an EGA card (which is addressed starting at 640K). MS-DOS on the Z-100 can run up to 1MByte Limit by turning off the Monitor ROM (top 32K addressed) and the video is already addressed by PHANTOMed address space. With 768K on the motherboard, a Z-205 card (WITH the switches SET PROPERLY To start at paragraph C000), the unmodified Z-100 will state 992K of usable RAM under MS-DOS. If you could turn off the ROM before MS-DOS boots (an OUT instruction can turn off the ROM), you would have 1MByte of usable RAM. Now the catch is: The Video shares 192K of address space with 'real' RAM (on the Z-205 or such) starting at 768K. The video is SUPPOSED to be normally off unless code is actually using the video RAM. You turn the video RAM on (any video RAM access will now PHANTOM in, turning off the 'real' RAM), use the video RAM, then turn it off (The video PHANTOMs away, and the 'real' RAM can be addressed normally). Well behaved programs (Compiled ZBASIC programs are not in this catagory) have no problems with this. Bad programs (violating ZDS recomendations for video access) turn the Video on in the beginning, and off at the end. If the program is ended (CTRL/C, etc) without the clean-up, it leaves the video on and it effectively swaps video bit plane data with your RAM disk (why RAM Disk, is next) unless you are running the MDISK from ZDS with patches made by Rob Logan that check for this. All this stuff will be posted in time.... Sionce most programs access the video during execution, the program MUST not be executing in the address space shared by the video RAM. Turning on the video while executing in the shared address space will cause the program to 'page' (PHANTOM in S-100 terms) itself out of existence (it will start executing in the video RAM). The safest way to prevent this curently is to set up a MDISK that occupies the addresses of the video space at the least and tell MS-DOS the start of the MDISK is the Top of its RAM (use RAMLIM.COM in the PD Lib). The ROM PHANTOMs in as well, unless turned off. I have not played with turning off the ROM during MDISK access yet, but it would allow for 32K more RAM for the MDISK. I run at home (have winnie) with 768K for MS-DOS and 224K for MDISK (Z-205) and at work (dual floppy) 480K for MS-DOS and 512K MDISK (224k of 512K is Z-205). It will all be covered in time in the ZUpGrade Series. I also want to point out that the ZUpGrade Series will explain old motherboard upgrades without the cost of the FBE (a fine product, though) kit, I don't like at all the idea of the FBE Z-205 card upgrade in the way it accesses RAM by removing motherboard RAM (Rob Logan has a much better way) and I am working on a non-Z-205 way that is much cheaper still. Cheers, An overworked Gern -------
andrews%cpsc.calgary.CDN@ean.ubc.ca (Keith Andrews) (03/25/88)
Gern's assessment on the problems with using the high order address latch to get at the upper 15Mbytes addressable on a Z100 is quite correct. However, if you have a Z217 board (hard disk controller) or equivalent in your system, you can use it to simply DMA (sorry TMA) the initial code into high memory. (whoever designed the Z217 should be commended: it does everything just like the ones in "real" [:-)] computers - which is more than you can say about the glorified floppy disk controller in IBM PCs.) Speaking of the Z217, the technical manual that comes with it gives some of the controller command and reply codes. However, there seems to be a few missing command codes. As evidence, the command and reply codes are grouped according to function: (this is from memory, the details are probably wrong) the 0X functions have to do with head motion (seek/restore), 1X are read functions, 2X are write functions and 3X are format functions. The manual also lists some 4X reply codes which have to do with diagnostics but there aren't any 4X command codes. Furthermore, there are holes within each fuction group (e.g. there'd be a 31 and 33 command code, but no 32). Does anybody know if there really are undocumented commands and what they might be? Keith Andrews andrews%cpsc.calgary.cdn@ean.ubc.ca