Peter's z80.eu site blog
http://www.z80.eu/blog/index.php
LBA 48bit vs 28bit BIOS support and DOS/Windows 98 FAT32 limits
http://www.z80.eu/blog/index.php?entry=entry211109-102817
LBA is not implemented for early PCs (but approx. since Intel 80386 CPU PCs raised), and unfortunately also later sold PCs have often only 28bit BIOS support. This is also mentioned on several web sites in relation with DOS 7.1 aka Windows 95B, Windows 98,SE (ME has a higher DOS number, but is not used standalone).
MS-DOS until Version 7.1 does not support FAT32, which theoretically supports up to 268.435.456 cluster - a cluster is usually a sector; before 4K block drives appeared, a harddisk sector had only 512 Bytes. That means you can use drives up to 2 TeraBytes.
Practically you will reach a lower limit often, 137GB. This limit is NOT related with FAT32, but with Microsoft tools like FDISK and FORMAT (in DOS 7.1) or with the build-in Formatting Routine in modern Windows implementations.
DR-DOS 7.03 with DRFAT32.SYS driver does support also FAT32, and so some unofficial published and modified versions of DR-DOS 7 (e.g. DR-DOS 7.01.06). Unfortunately DR-DOS has still a 2GB limit for the first partition. But give FreeDOS also a try, this will work for sure.
If you want to use larger harddisk drives with DOS 7.1 (at least larger than 64GB), you need a corrected version of FDISK. You will not find the file anymore on Microsoft pages, but to the rescue, archive.org has still them.
Follow the "related link" below to visit the original archived Microsoft page (saved from pkisolutions.com) or search for file "263044usa8.exe" (english) or "263044ger8.exe" (german).]]>Ontrack Disk Manager adventures
http://www.z80.eu/blog/index.php?entry=entry210819-153000
E.g. if you find >a version 6.03 with "Conner Peripherals" branding<, it can be used with a Seagate drive ;-)
This is the main menu:
And this happens after pressing return: Remember, existing disk content will be deleted...
And that comes up than:
If successfully installed, booting from hard disk drive looks like this:
If manually (see more below) installed on floppy disk, booting looks like this:
You do not need to have the Disk Manager Driver DMDRVR.BIN loaded while using the main program DM.EXE with a boot floppy disk for installation!
Later on, if you want to boot from diskette for whatever reason, you have to include some files from the Disk Manager diskette.
CONFIG.SYS for a MS-DOS 6.22 boot diskette should be looking like this: DEVICE=DMDRVR.BIN DEVICE=HIMEM.SYS DOS=HIGH ... assuming that the following files must be present on diskette: DMDRVR.BIN XBIOS.OVL HIMEM.SYS ... and of course other, usually used files for a MS-DOS boot diskette.
You SHOULD NOT load DMDRVR.BIN after HIMEM.SYS, but only before ! (see also >here< for an official statement)
Any other additional commands can follow after DOS=HIGH, but must not.
AUTOEXEC.BAT needs no special command, can include just your KEYB command with an appropriate two-letter country abbreviation.
All tests were done using PCem/86Box with an emulated 386DX40 and with Award BIOS, and with the following drive parameter: User Type 47: 2047 tracks, 16 heads, 63 sectors (~1007 MB)
Interesting fact:
Booting from floppy disk without DMDRVR.BIN and showing partition infos via FDISK results in a 504MB sized drives (which is wrong). Booting from floppy disk with DMDRVR.BIN (and XBIOS.OVL) shows the correct partition/drive size.
Added later: Disk Manager Version 7.09 and may be also other newer versions will not use DMDRVR.BIN loaded as a device driver, instead, the boot sector of the floppy will be modified to load DDLOADER.BIN. This can be done by using DM.EXE and "Maintenance" tasks.]]>Comparison of free memory for an old IBM PC/XT compatible system
http://www.z80.eu/blog/index.php?entry=entry210807-180000
MS-DOS 1.25 : 642784 english MS-DOS 2.00 : 628688 english MS-DOS 2.11 : 630784 english MS-DOS 3.00 : 616720 english MS-DOS 3.10 : 616800 english MS-DOS 3.20 : 609984 english MS-DOS 3.30 : 600368 english MS-DOS 3.31 : 599488 english (Compaq DOS, first DOS for partitions > 32MB) MS-DOS 4.01 : 589488 english MS-DOS 5.00 : 593392 english, no HIMEM.SYS MS-DOS 5.00 : 638592 english, with a 386, and with DEVICE=HIMEM.SYS and DOS=HIGH MS-DOS 6.22 : 592384 english, no HIMEM.SYS MS-DOS 6.22 : 638416 english, with a 386, and with DEVICE=HIMEM.SYS and DOS=HIGH
MS-DOS 4.01 : 589072 german version (just to see if a different language costs memory)
HIMEM.SYS 2.04 can be loaded on a 386 with MS-DOS 4.01, but there is no DOS=HIGH command, about 2.6KB less memory then (if loaded), DOS 6.22 without hidden DRVSPACE.BIN file in root directory.
There are no further numbers for comparison of higher DOS versions, because it makes not really sense to load such a version on a very old 8088 PC compatible system. Also, I do not wanted to compare the free memory numbers for 386 systems and above, with UMB usage you can probably get even more free memory than just with DOS=High.]]>Hard Disk Imaging Utility for (very) old PCs - now in beta status
http://www.z80.eu/blog/index.php?entry=entry210331-173000
So far it does already creating a whole image backup of a HDD, and it compresses also (at least down to about 60% of the original size) the image file chunks which can be created. That means, on the target media (like a ZIP 100 media), about 160-170MB can be stored, instead of 100MB (remember, it's NOT 100MB in fact, it's about 91MByte).
It requests for exchanging the target media, so you will be able to use subsequently different media disks, instead of saving it first to another HDD (caching it).
See the screenshots I made:
Starting it, choosing the right HDD and size of the target media (parts):
Finishing it, looking for the result:
Unpacking it to uncompressed image parts, and reassembling it to one HDD image file: (even if you rename the compressed files, the sequence number, which is important for reassembling, is stored within the file header of each file)
Looking for the result:
You can download the 1.3 (still improving it) at "related link" here.
The "unpack" Windows application (to uncompress the saved & compressed imagefile parts to uncompressed imagefile parts but with the help of the Windows command line, running with Windows 10 for example) is now also available >here<. Using the saved image file is tested more than once with PCem for example. And last but not least, I'm working meanwhile also on the topic "restore", means you will be able to restore that saved image back in the future.]]>Strange DOSBOX (with latest version 0.74-3) behaviour with a sample benchmark program
http://www.z80.eu/blog/index.php?entry=entry210208-095857
This program, created with an assembler source for MASM 5.10, will measure basically for a defined period of time (5 seconds, or in 1/18.2 sec ticks exactly 91 ticks) how fast one char is displayed with the help INT 10h function 09h (a BIOS function, not DOS related). I was trying to implement it via INT 10h function 0Eh (tty type output), but this was not working because function 0Eh is working only in graphics mode. I didn't liked to implement it by writing directly into video RAM (beginning at 0B800:0h for CGA, EGA and VGA), because I wanted to avoid screen snow with a CGA.
I tested it with several virtual, emulated PCs (from IBM PC/XT up to a PC with a Pentiumn 233 MMX), and also with some real, existing PCs I had.
Usually, DOSBOX, especially if the cycle value is increased or unlimited, but also even with the default settings, is really fast and things will work really good.
With my sample bench program, this ends up in a surprise ! DOSBOX wasn't the fastest choice. It started very fast, but after a moment, was slowing down drastically with the video output. I didn't try to analyze the reason (by reviewing the DOSBOX source), but it was interesting. PCem with the emulated Pentium MMX 233 was way faster (~ 982 loops for DOSBOX, ~ 1700 for the emulated PCem v17 PC). I guess I need an explanation why this happens, but I fear emulated PCs (using PCem) with a real BIOS are much better in terms of (text) video output, because there is no caching or memory limit while executing the emulation.
Added later: It depends of the "cycle" value, if the value is above ~4000 (or even "max"), you will get the mentioned effect, if it's the default value of 3000, the effect is almost invisible. But still a strange effect.
See 'related link' for a download possibility of the benchmarking program (with source code). See also my >youtube video<.
I would really, really appreciate some result values from REAL machines. Many thanks for any value in advance. You can use the comment function (at least for about 60 days after posting this) and/or the contact function here.]]>Ghost HDD imaging history ... Wikipedia ignores versions below 3
http://www.z80.eu/blog/index.php?entry=entry201228-155943
But it wasn't published by Symantec first. Binary Research started to sell Version 1.0 (1.1) in 1996, followed by Version 2.0 (2.07) and Version 3.0 (3.1) - latest minor version in brackets. The first 2 versions runs even with an IBM XT and without extended memory. Starting with Version 3 it uses XMS and needed a 286 CPU, Version 4.0 uses Pharlab Extender, but is still running at least with a 286. Starting with Version 5.0, it's running with an 386 and higher. So, if you want to create a hard disk drive image for an IBM AT clone, you can go on with Ghost 4.0a, and the best, it can still be read by later Ghost versions (e.g. with Ghost Explorer). So that could be a way to virtualize your HDD content (and running it with VMWare, VirtualBox or PCem). For the first 3 versions valid: It can also run with OS/2.
I have made some screenshots, the first 4 versions are running in text mode, starting with Ghost 5, it is a graphics screen with VGA resolution.
This is version 2.07: and
Version 3.1a: and
Version 4.0a: and
Well known, starting with Version 5, all later versions having the same look alike: and
Ghost Version 1.1 did not support FAT32, starting with Version 2.0 it had support for FAT32. Both run with conventional RAM only, too. Since Ghost 3.0, partitions can be imaged as well as a whole drive, but XMS is needed. Ghost 4.0 images can be read from later Ghost versions. Ghost Version 5 breaked the 8GB (BIOS) barrier.
Btw. Wikipedia does not list up earlier versions than 3. My blog entry does this ;-) ]]>Remarkable site and blog: The 'Computer History Museum'
http://www.z80.eu/blog/index.php?entry=entry201221-104917
The 'Computer History Museum'. The blog is still actualized regularly, and points out many historical facts beside of other more ore less computer related facts but also opinions.
The site itself does NOT only shows vintage computer technology, but covers also infos about 'remarkable' people, and beside this, it has a very interesting corner named "Internet History Program Archiv". It's NOT an archive like www.archive.org, it's moderated and selected. It lists up also recent and upcoming computer history related events in the U.S..
I like the concept in general also, because you will still find interesting entries even after your 10th visit, very good. It's like a kind of mirror of the "old times", like a time travel. ]]>Two interesting pages about the Olivetti M20 - one of the few computer which have a Z8000 and can run CP/M-8000
http://www.z80.eu/blog/index.php?entry=entry201215-222508
http://retrocomputing.altervista.org/m20/m20.html
To get an impression from what I'm talking - here's an image from an M20 machine, running CP/M-8000 (click on the picture to zoom):
The machine was selled in 1982 with PCOS (that's an operating system with cryptic commands, even more cryptic than CP/M was)...
There was an additonal 8086 card available to run MS-DOS, but that's another story. The cpu was - to document it more accurately - a Zilog 8001, the cpu family is named 'Z8000'.
Still one of the most "rich" web pages about the Olivetti M20 can be found at http://www.z80ne.com/m20/ ]]>Off topic: Microsoft Safety Scanner ... not really recommendable. See why.
http://www.z80.eu/blog/index.php?entry=entry201117-120000
I tested this tool a few times, but I found some points really annoying, beside the fact it also helped to find some WM97 Downloader variants not found by Symantec Endpoint Protection for example.
It is very slow, despite of the choice you're taking at the beginning of the scan process. It can take hours to be finished.
Also, it does not only find malware, but also network tools, and other useful tools e.g. found at Nirsoft's page. You can't choose what type of files you want to scan.
It cannot handle less established archive formats. It scans even ISO images, report findings, but let the ISO as is (this can be also an advantage, though).
At the end, it does not ask what to do with the findings. They/it will be moved into quarantine. There is no possibility to make a decision for each file, nor how to deal in general with findings.
You can't restore files from the quarantine (files are encrypted). So may be you need a backup before scanning with MSERT.
I would recommend (for unencrypted drives) to use ESET SysRescue Live instead for scanning "offline" for malware.]]>FMA 3500, a 486DX Notebook with monochrome LCD VGA display
http://www.z80.eu/blog/index.php?entry=entry201010-190000
It runs Windows 95, but it has not enough space on hard drive for Windows 98 or newer, and I guess it would be to slow for Windows 98, too. But for a monochrome display, it's acceptable, there are other more worse displays existing. It was sold also from the german computer distributor "Vobis" as "Highscreen 486DX Notebook".
Btw. - the often found "one EXE file version" of Johnny Castaway Screensaver (made by someone for Windows XP) is NOT compatible with Windows 95 (but with Windows 2000 and XP). You need to look for the original setup disk content (e.g. at winworldpc.com) to be able to install it. See also "related link below".
This software "Mephisto Meisterschach" is really a rarely used software, but still very interesting, because it plays very well (compared to the similar old Chessmaster 4000, much better).]]>