HAL had this cousin, see?

[My 6581]
Dude, it ain't no Dell:)

So, what's a 6581?
Some Select-a-Bus Links
Why we know HAL is a close relative
Matching task to machine (the Zen of microcomputing?)

So, what's a 6581?

Okay, so defining something by what it's not is pretty dumb. It is an IBM 'Select-a-bus' Personal Computer, in my case ISA/VESA bus. The concept's actually kinda cool - a PC that is not limited to one solitary bus architecture. and there's a couple of mixed-bus architecture critters out there, they had some nifty features beyond the mixed-bus architecture, such as PCMCIA card bay provisions, pretty decent expansion capabilities (espescially in the 6x8x critters). 25Mhz 486's were the slowest processor supplied. Like PS/2 machines, the target audience was business: the machine here used to be a teller workstation for a bank.

Just to give you an idea of what bus hybrids were available... ripped from the 'IBM PC and PS/2 Pocket Reference Manual' IBM document S41G5086-03:

PC 300/700 Family:

6571    6581    ISA/VESA  
6573    6583    ISA/PCI
6575    6585    ISA/PCI
6576    6586    ISA/PCI
6875    6885    ISA/PCI
6876    6886    MCA/PCI

Some Select-a-bus links

Why we know HAL is a close relative

Well of course there's the theory of proximity: HAL came from Champaign-Urbana IL and I'm just down the road in Decatur. It has some oddities about it that... well, have made life interesting from time to time. Of course, Operator Error has probably entered into one or more of the following oddities on more than one occasion...

  • 6581 oddity #1. I can't locate this thing in IBM documentation, can find other 6581 machine info, just not for model H3A. Check out the Product Index Table above... don't see any H3A submodels, do you? As much as I think I sure am a special guy, I doubt Big Bad Blue would have built a unique machine just for me:).

  • 6581 oddity #2. Rapid Resume/APM. Currently disabled - do you have this problem? I do have an early 66/486 in place of the original 33/486, so this does in fact apply to me. IBM describes the APM failure here, where early 486's don't support the VME functions required by APM. This, at least, is something I can explain.

  • 6581 oddity #3. Memory Identification. I can't explain this one: Machine says (by way of BIOS setup program) that it will accept parity SIMMs. Every parity SIMM I've tried gets kicked out as unrecognizable. It currently has two 4MB and one 16MB SIMM installed, all of which pass DOS-based diags. But (and this is why I *really* can't complain about a single thing if this critter acts peculiarly) they're not officially-sanctioned IBM SIMMs. If you want to avoid this problem and yourself have a Select-a-Bus machine, check out officially supported SIMM FRUs.

  • 6581 oddity #4. Mysterious OS/2 freezes. (Of course, he who actually admits to using incorrect memory for the machine deserves NO sympathy.) Am unsure of the true nature of this problem; Had a recurring problem where accessing the FDD would cause a complete system freeze - sometimes. Switching focus away from the floppy-related activity did seem to guarantee a system freeze, but even did have the machine lock up solid even when focus remained firmly on the floppy task at hand - e.g. XCOPY in a command-line session. WPS or command-line, PROTECTONLY or no. This was using the 16MB SIMM only (remember DOS-based diags say this SIMM is good, state FDD is good), OS/2 2.1, Warp 3, 4, Fixpacks 40 or 12 respectively applied or not.

    Possible sources for this Oddity might be memory... or a Maxtor HDD, according to this IBM document

Sometimes... rather than fight the tide you have to just bobble along with it. Forcing the 6581 into Warpdom was clearly not happening, at least not with the right SIMMs it's not. So it sat unused for some time... until I wanted to adventure back out into the world of DOS.

Fast DOS Box

So... what the 6581 does an exceptionally good job at, is be an extraordinarily fast DOS box. I was wanting to play around with the Arachne Web Browser (see also HERE)... but in a timesliced OS/2 VDM performance was less than exhilirating. On the 6581, I have more than enough XMS memory to be able to run both a decent-sized SMARTDRV cache as well as load the entire Arachne browser onto a RAM disk. Why would a person want to do that?

Arachne, quite simply is the first software product in a long time that I've been amazed by. It is a fully-featured WWW browser with a mail client & DOS PPP driver... and it works exceptionally well. My only complaint (such that it is) is that as a longtime OS/2er I've gotten used to the whole idea of CTRL-ESCing or ALT-TABbing to another task while I'm doing something else. Lemmie tell ya, CTRL-ESC & ALT-TAB are hard habits to break. Arachne shouldn't be run from DOSSHELL task-switching environment (so cautions it's designer, Michael Polak). But, once you have these DOS-based restrictions in mind, Arachne proves to be a very capable browser, doing frames, ftp'ing, all sorts of good stuff, with a minimum of resource use (like anything else, it's always happier with more... but Arachne's resource use is but a fraction of a fraction of some other well-known browsers - Yo! Netscape- Take note!)

This has allowed me to use the 6581 for some happy & fruitful purposes, finally. I get to play around with DOS again - which, if limited when compared to OS/2, does offer a wealth of tinkering possibilities:) And I probably haven't completely given up running Warp on this machine yet; indeed, the 6581 ultimately has greater expansion capabilities than the 9577, provided I use the correct parts.

Content created and/or collected by:
Louis Ohland, Peter Wendt, William Walsh, Kevin Bowling, Jim Shorney, Tim Clarke, David Beem, Tatsuo Sunagawa, Tomáš Slavotínek, and many others.

Ardent Tool of Capitalism - MAD Edition! is maintained by Tomáš Slavotínek.
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