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UCSD p-SYSTEM for IBM PC - bootable and not MS-DOS related, not the usual file 
Saturday, August 26, 2017, 12:00 PM
Posted by Administrator
Looking for the Pecan UCSD Pascal / p-system disks (which can't be found for download in the Internet), I digged out two disk images while visiting an almost unknown forum.
Because the images were in IMD format, I had to unpack them first with IMDU before I can try it with a virtual PC (VMware Workstation etc). But the images were not usable (or seems to be not usable). But I didn't stop trying and I also took PCem for it, and while choosing an "IBM PC" for emulation, it suddenly works (it stops booting for about 10 secs, but went on working, showing the start menu selection !).
So the first learning was, it does ONLY run on 8088/8086, not on a later Intel CPU (like 286, 386 a.s.o).
This is it after booting (doing nothing else):

And these are the contents of the two disks, showed with "(F)iler":

Last but not least this is the (unusual) editor:

The disk images are in RAW format, and have a structure of 40 tracks, single sided, 8 sectors/track. Not sure if this can be changed to an other disk format, because you have to change the p-System code also.

See related link for the attached ZIP file with the disk images.

P.S.: I have also a page for UCSD software, see >here<.
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ATI EGA Wonder used in / for an IBM Portable PC 
Saturday, May 27, 2017, 03:00 PM
Posted by Administrator
Promised, this is the last entry about the (beautiful) IBM Portable PC 5155.
I replaced my original, really long CGA card with an ATI EGA Wonder (first series).
And I was surprised how good many EGA capable games are looking.

EGA high resolution with 640x350 pixels don't seems to work with the composite monitor:

But "Blockout" (a 3D Tetris alike DOS game) DOES work with 640x350 pixels. So it seems that some games forces a higher vertical frequency and some not. You have to try what game does work and what not...

But mid res EGA (320x200x16) does work always, and looks very nice:

(this is Arkanoid II, Revenge of Doh)

And of course, CGA games are still possible:

(this is TAPPER, a real classic for the PC/XT category computer)

Also, 640x200x16 (EGA high res with 200 lines) is also possible with the build in CGA composite monitor of the IBM Portable PC.

Btw. > does NOT list the used ATI EGA Wonder<. This version has 3 large integrated chips, 2 from CHIPS Technology and one gate array chip from National Semiconductor, named "SCX6244":

Unfortunately the original software floppy disks can't be found anymore, I only found the "SMS.COM" video mode switching program for DOS.

To show PCX images, I used 2SHOW (CompuShow 2000, runs on a plain IBM PC/XT and can also display JPG for example).
Many image viewer and converter for DOS can still be found, see "related link".
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A word about 'Spinrite' ... a repeatedly echoed myth from many forum users 
Saturday, April 29, 2017, 01:00 PM
Posted by Administrator
Spinrite is a hard drive diagnostic software, and was first published in 1987. The last version 6.0 was published in 2004. Before I go on with my explanations, remember, Spinrite should be necessary only for MFM and RLL drives, modern IDE drives have their own defect management.

Last time I recognized my IBM Portable PC has at least 110KB clusters marked as bad. But I didn't expirienced problems so far (read or write errors), so I was happy. But even 110KB are space which you could need, so I decided to "refresh" the 20MB MFM hard drive with Spinrite II. After 4 hours only 15% were processed, so I decided to stop it with pressing ESC, which is NOT a hard break, Spinrite finishes it's last action (last processed cluster).
Now I tried to boot again and guess what, NOW I had read errors. Also, the drive seeks desparately for a readable sector often. CHKDSK results in 250KB bad clusters.

This was surprising for me first, because BEFORE I started Spinrite, there was no noticeable error !
Also, I got many defective directory entries, which I could NOT REPAIR with CHKDSK /F.

But meanwhile I understood what happened. For such an old MFM hard drive, this is a torture or at least stress. So instead of doing something good, I tried to kill my MFM hard drive.
A full Spinrite run take many hours, and can't be compared to a normal load of software usually used for such a computer.

So the best idea is NOT USING SPINRITE SNAKE OIL, instead, try to backup what you want first, start low level formatting by using the controllers BIOS (start DEBUG, enter "g=C800:5"), then boot with a working DOS floppy disk, use FDISK and FORMAT C:/S, and restore the saved files back. Last but not least, as already stated, the processing time of Spinrite is far too high - it can take days, not hours. A low level format by using DEBUG take minutes only but refreshs the sectors (re-magnetize them), too.

If in doubt about the drive health, you may use a DOS 6.2 (6.22) boot disk with SCANDISK, to detect unreadable clusters. I recommend NOT TO USE Spinrite, because your old drive will hate you for it. Believe me.

SCANDISK should be called with the parameter /SURFACE and for monochrome screens with /MONO, too.
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Got an IBM Portable PC 5155. Really slow, but it's a nice engineering piece. 
Sunday, April 23, 2017, 09:00 PM
Posted by Administrator
This Portable PC is heavy, but it's an IBM PC/XT in a case with a build in amber CRT screen.
It's factory configuration only includes 256KB RAM, an IBM PC floppy controller and a CGA graphics card. The internal screen is feed by an FBAS (Composite) video signal (and not with 9-pin connector).

An original 64-256KB memory card was installed, which results in 512KB in total.
But I managed to add interface cards, and I replaced the original memory card with a Mycomp MEMS memory card, which can be populated with gigantic 2048KB RAM, and this card can offer conventional *and* expanded memory (at the same time).
In the screenshot, you can see the result after it was booted (IBM DOS 5.02 is used).

Believe me, repairing or just changing the cards, DIP switches or memory chips on the mainboard is *NO* fun. Inside the case it's really (over)crowded. But on the other side, in terms of mechanical quality, this PC seems to be very good quality.

Take a look at the 'related link' below, if you are interested in further details.
add comment ( 180 views )   |  permalink   |  related link   |   ( 3 / 1967 )
Amstrad PC1640 on steroids ? Not really, but still a surprise... 
Monday, March 13, 2017, 12:30 AM
Posted by Administrator
Recently I got some problems related with an Amstrad PC1640, the floppy drive was not working properly (formatting and read errors, also when reading disks, formatted on the Amstrad, but on a different PC). So I decided to replace the floppy drive, which is in fact a very unusual, belt driven OEM Alps drive (DFD222A01, Amstrad part no 40046).
The first surprise while opening the PC1640 - I discovered a small additional pcb which was connected with many cables to the area on the mainboard the crystal is located.
There was also a 3-way switch to change the frequency from 4 MHz to ~10 Mhz.
The additonal board and the switch is marked green in the picture below.

Also, I discovered (never used it) an Intel 8087 (marked light blue in the picture) !
This might be useful when using one of the first AUTOCAD versions.

Regarding my wish to replace the floppy drive - this was a desaster. I was reading >John Elliott's Amstrad hardware compatibility page< and hoped that my TEAC FD-54B can replace the original drive.

But you can't replace that floppy drive for two reasons:
a) the metal cage for the floppy drive does not have the correct "holes" at rear...
b) even if you take a saw and make the holes bigger, the new floppy drive still does NOT work

I know the jumper settings has to be changed from (IBM PC compatible) DS1 to DS0 (because of the twisted cables of the IBM PC), but the Amstrad ALWAYS SAYS the floppy controller has problems with the drive. Also, the motor light was always on, which points to DRIVE SELECT problems. But DS1 doesn't work too.
Also, rotating the cable connector ends up also in drive light always on problems but the floppy controller do not show up the error message.
So I decided to check again the original Amstrad floppy drive, turning the motor (with the belt), and also checked the drive head movement. I didn't recognized any problem, so I exchanged the non-working TEAC FD-54B with the Alps OEM drive (the Amstrad one) back.
After reassembling, it suddenly worked without errors. Strange.
add comment ( 187 views )   |  permalink   |  related link   |   ( 3 / 1923 )

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