Peter's z80.eu site blog
An odyssey with an 8bit Seagate SCSI controller ... 
Tuesday, March 25, 2014, 09:40 PM
Posted by Administrator
Not funny, but instructive.
I've tried to add a bigger SCSI drive to my PC/XT system, which uses a Seagate ST-02 controller. At the moment, it runs well with a small Conner 3040 HDD (= 40MB), but I liked to have a bit more HDD capacity.
So I obtained a Seagate ST51080N, which has in fact 1080MB capacity, but still a 50 pin interface. Unfortunately I was able to read some messages about Seagate ST-02, which describes a limit for bigger HDDs - but not clearly described what limit, but it seems to be related with the older ROM version of the controller.

So I decided to upgrade the BIOS from 3.0 to 3.32, found at http://ftp.mpoli.fi/hardware/ROM/SEAGATE/ ... but someone made a mistake describing that ROM.
It was NOT Seagate SCSI BIOS V3.32, but SyDOS SCSI BIOS V3.35 (but still based on Seagate's SCSI ST-01/ST-02 BIOS). It had some additions for Sygate's EZ135, which sounds nice, but was not helpful for getting bigger drives working properly.

I ended with using the Conner 3040 again, which works with the old BIOS version as well as with the new BIOS version.

Conclusion: Don't trust on file descriptions, nor on user messages about compatibility of old hardware. Seagate's ST-01/ST-02 is only able to operate with drives less than 1024MB. Nothing else.
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All time TOP DOS Games (1982-1993) 
Sunday, March 16, 2014, 12:20 AM
Posted by Administrator
Excuse my conversion to a picture, but simplephpblog does not support tables.

Introduction of VGA in April 1987 changed all, so my list seems to be less complete from 1988 towards...
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Windows Chicago Alpha / Pre-Beta Boot Screen and other... 
Wednesday, March 12, 2014, 08:55 PM
Posted by Administrator
Take a look at
http://monkey-hole.co.uk/esa/os/
for very early beta versions of Windows, there are even virtual machines (for Microsoft Virtual PC) to try something strange like Berkeley 2.11 BSD.
A bit simple/poor boot screen also for Windows Chicago Build 73, although it's very rare:


To remember: There is also an interesting blog which covers a lot of different virtual machines: http://virtuallyfun.superglobalmegacorp.com/

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Different Floppy Drive widths ? What did IBM wrong ? Or others ? 
Sunday, March 9, 2014, 08:00 PM
Posted by Administrator
Original 5.25" floppy drives in IBM PC or IBM PC/XTs are less wide than later selled floppy drives from other vendors (like TEAC or EPSON), that means 145mm from IBM, 147mm from others. And so 3.5" drive adapters are also too wide.
I was trying to add a second 3.5" floppy drive, but I couldn't. After 10 minutes, I gave up - I have the finding to rasp something from the side frame (about 1mm from each side).
This is really annoying. Only after expiriencing this for myself, I was able to find something about it in vintage-computer.com forum ... and all that after more than 30 years of IBM PC launch :-(
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IBM PC/XT building site ... replacing cards and drive 
Sunday, March 2, 2014, 11:53 AM
Posted by Administrator
After recognizing many errors while reading and writing files on my MFM hard disk drive, I decided to exchange my hard disk drive with a SCSI one.
This resulted in a longer search for an appropriate 8-bit ISA bus SCSI controller, my favorites were Future Domain TMC-850 and Seagate ST-02. I was able to swap some ISA cards with a Seagate ST-02 finally.
Because this Seagate ST-02 also supported (physically, see note below) high density floppy drives, it came in my mind to add such a floppy drive, too.
This wasn't so easy as I thought, because the mentioned Seagate ST-02 controller didn't support HD floppy drives by included BIOS. Instead, only hard disk drive support is added by that BIOS :-(
So I had to look for an alternative solution. I tried "800.com", a BIOS extension from an italian author, but it doesn't work too. Luckily there was a working solution left, "2M30", which includes a BIOS extension 2M-XBIOS.EXE (you have to include it in your CONFIG.SYS).
Also, I had to figure out how to initialize that SCSI HDD, it worked not only with debug, but also with this nice small utility named "FINDINIT".

That's how it looked after several attempts to get it working. But I finally managed it, thanks to the 2M utility (see related link also):


P.S.: I found also a device driver named JDRDISK.SYS, mentioned in the vintage-computer.com forum. I had to patch it to get it running, because DOS version check was very strange implemented. Try for yourself, it still didn't worked for me to use HD drives with it.
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