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 Almost 500 brand new IBM 8086 machines on Ebay! View next topic
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PostPosted: Thu Sep 08, 2005 1:15 am Reply with quoteBack to top

Sweet as hell...447 available, all brand new in box! PS/2 model 25, 8mhz...these are ISA too, so they'll take your XT cards!

However, check the specs first:

8525-001:
8mhz 8086
512KB RAM ( a few DIP memory chips and you're at 640K)
One long and one short expansion slot
Built in IDE on the motherboard
720K diskette drive
Built in MCGA graphics and mono VGA monitor (320x200x64 grays, 640x480x2 b&w)
8087 socket

However, the one long and one short expansion slots limit you severely as to what you can install...i.e, you can't put in an EMS board, a sound card, and a network card like I would want to.

http://cgi.ebay.com/IBM-MODEL-25-DESKTOP-PC-8525001-8086-8MHZ-NO-HDD-L-K_W0QQitemZ5160748811QQcategoryZ51096QQcmdZViewItem
xtguy



Joined: 02 Oct 2004
Posts: 28
Location: the mile high state, Colorado

PostPosted: Fri Sep 09, 2005 11:02 am Reply with quoteBack to top

Beware though everyone, the built-in IDE on the P/S 25 (and P/S 30) is a non-standard, proprietary IDE connection, it will only work with the specific hard drive made for this machine and not a typical 16 bit IDE drive, nor will it work with the so-called "8 bit IDE" drives that were available for a couple of years.

When IBM introduced the PS/2 series in April 1987, an IDE standard had not yet been written, so IBM designed their own completely non-standard interface,

The IDE drive on the PS/2 Model 30 (8086) is even slower than the 10 meg. ST-512 drive on the IBM 5160 of 1983! My Norton Utilities gives the speed of the drive as 0.9x the speed of the 1983 IBM XT (with the 10 meg. drive).

The PS/2 25 and the P/S 30 will not work with the V20 upgrade chip, and I have been told that the built-in MCGA video cannot be disabled, so you cannot add in a different video card (although I haven't tried it myself yet to confirm).

I'm not surprised somebody somewhere is "stuck" with nearly 500 of them.
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mf_2



Joined: 02 Oct 2004
Posts: 365
Location: Stuttgart, Germany

PostPosted: Fri Sep 09, 2005 11:11 am Reply with quoteBack to top

can't you juts put in a real ide controller in an isa slot? I don't knwo, I never even saw a ps/2 and so of course I never got to use one. but I think the eraly ps/2s had standard isa slots, instead of being mca only.
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bear



Joined: 04 Oct 2004
Posts: 172
Location: 57�59'N 15�39'E

PostPosted: Fri Sep 09, 2005 7:01 pm Reply with quoteBack to top

Is the IDE like RLL or is that different too ?
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ryan no log
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PostPosted: Mon Sep 12, 2005 8:48 pm Reply with quoteBack to top

Isn't this a bad implimentation of ESDI? I never remember my 25 as having any sort of IDE slot.
alibaba



Joined: 29 Jun 2005
Posts: 7

PostPosted: Wed Sep 14, 2005 2:06 am Reply with quoteBack to top

[/quote]
Of course, RLL is old and a different technologie than IDE.
RLL drives are like MFM drives, except that they use diferent encoding to store data.

In fact, MFM drives could be used with RLL controller if low level formated with RLL controller, but will probably not work relialbly because MFM drives were not designed for RLL encoding.

(These facts come from what I remember to have read from some documentation and should be mostly true).
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PostPosted: Fri Sep 16, 2005 4:55 am Reply with quoteBack to top

alibaba wrote:

Of course, RLL is old and a different technologie than IDE.
RLL drives are like MFM drives, except that they use diferent encoding to store data.

In fact, MFM drives could be used with RLL controller if low level formated with RLL controller, but will probably not work relialbly because MFM drives were not designed for RLL encoding.

(These facts come from what I remember to have read from some documentation and should be mostly true).[/quote]

MFM and RLL drives are very wacko beasts with a very chaotic way about them from my experience.

Case in point. I had 2 ST-506/412 drives: a Seagate ST-238R, and an ST-225, one RLL, one MFM, and I would run them in my old XT clone off of a Western Digital WD2400X (or something like that) series controller. If I had them both installed (238 as master, 225 as slave), both drives worked perfectly without errors assuming they were in the same exact position they were when low level and FORMAT.COM formatted. However, the catch was, that when the ST-238 had run for awhile, it would start getting data seek errors.

Skip ahead, I decided to take out the 238 and try the 225 on it's own. The 225 did not even make it past the low level format! Go figure. The ST-238, however, worked perfectly without a single Drive Seek error, and this was the time I left the XT on for THREE DAYS STRAIGHT! There were no missing allocation units, only 2 bad sectors, and the performance was MUCH better.

Very weird how the ST-225 functioned as a 30 MB RLL drive when slaved to a real RLL drive, yet would not work on it's own.
creepingnet



Joined: 19 Oct 2004
Posts: 137
Location: Lynnwood,WA

PostPosted: Fri Sep 16, 2005 4:57 am Reply with quoteBack to top

Anonymous wrote:
alibaba wrote:

Of course, RLL is old and a different technologie than IDE.
RLL drives are like MFM drives, except that they use diferent encoding to store data.

In fact, MFM drives could be used with RLL controller if low level formated with RLL controller, but will probably not work relialbly because MFM drives were not designed for RLL encoding.

(These facts come from what I remember to have read from some documentation and should be mostly true).


MFM and RLL drives are very wacko beasts with a very chaotic way about them from my experience.

Case in point. I had 2 ST-506/412 drives: a Seagate ST-238R, and an ST-225, one RLL, one MFM, and I would run them in my old XT clone off of a Western Digital WD2400X (or something like that) series controller. If I had them both installed (238 as master, 225 as slave), both drives worked perfectly without errors assuming they were in the same exact position they were when low level and FORMAT.COM formatted. However, the catch was, that when the ST-238 had run for awhile, it would start getting data seek errors.

Skip ahead, I decided to take out the 238 and try the 225 on it's own. The 225 did not even make it past the low level format! Go figure. The ST-238, however, worked perfectly without a single Drive Seek error, and this was the time I left the XT on for THREE DAYS STRAIGHT! There were no missing allocation units, only 2 bad sectors, and the performance was MUCH better.

Very weird how the ST-225 functioned as a 30 MB RLL drive when slaved to a real RLL drive, yet would not work on it's own.[/quote]

That was me above, forgot to log in (not on my normal computer)

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alibaba



Joined: 29 Jun 2005
Posts: 7

PostPosted: Fri Sep 16, 2005 6:12 am Reply with quoteBack to top

First of all, one drive controller is MFM or RLL, not the both. If I'm wrong, tell me.
I suppose your controller is MFM. So, your RLL drive works like MFM , because it is low level formatted like that.

If one drive (MFM or RLL) encounters seek errors, it may be the sign to low level format the drive. In this way, new bad sectors will be detected and marked as bad, so you will not use them anymore.

Whether your drive is slave or master does not matter in my opinion. A drive may need to be low level formatted if used with an another controller and has not been low level formatted with that controller.

If something up there is wrong, you can correct me. Maybe you knew these facts too.
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PostPosted: Sat Sep 17, 2005 1:10 pm Reply with quoteBack to top

This is why I use a Seagate ST02 SCSI controller in my portable, it's *actually* portable with the hard drive in it now, unlike how it was with the ST225 that came in it Razz

Much more reliable too! However it does seem to be picky about what drives it likes.
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