Date   : Wed, 20 Jul 2011 18:15:30 +0200
From   : rick@... (Rick Murray)
Subject: Emulating the 80186 CoPro on an ARM CoPro

On 20/07/2011 09:40, Pete Turnbull wrote:

> (I believe Rick meant to post this to the list, so I hope he doesn't
> mind me replying in public)

Yes. Hit Reply on my phone, end up PMing you. Seems to me the Reply-To 
should point to the list...?


> A PS/2 Model 60

That's the one. Had its setup via a special system disc (what, no BIOS 
config!?). Can't recall how often dozy-bloke misplaced that floppy. ;-)


> I recall Acorn making a bit of thing about that at a BETT show (1988?),
> because the PC Emulator did all those things, while RML's then-current
> 80186 "PC" offering didn't.

Ah, yes. I recall the irony of a functional software creation being 
better than a hardware one.

But, then, my first PC was a V30-based XT with ST506 harddisc (a 
whopping 10Mb!), dual serial cards, Hercules display (!) and some sort 
of interface that looked like a SCSI socket but I never figured out what 
it was [the board said IEEE and a bunch of numbers]. So I guess from 
that, pretty much anything was going to be more compatible. Most of the 
stuff I tried looked at the graphics card and aborted with a "WTF?" 
error. ;-)


I guess this is the fundamental difference between the Acorn (& Mac) 
mindset and the PC world. That in our bubble the computers are designed 
to a specification and a broadly compatible. Sure, there are many types 
of Beeb (A -> Compact) with and without co-pro, differing FDCs, etc, but 
in general things are very similar across the range as one company made 
them and compatibility was important enough that the later (RISC OS) 
family came with a pretty good B emulator as bundled software.

Conversely the PC world where supposed compatibility is accepted, but 
the big rules are innovation and cost-cutting, often at the expense of 
this compatibility. We still see it today when such-and-such an 
interface has specific behaviour depending on where it is installed, and 
what with. Example - my Presario had a TV capture card and a network 
card. But I could NOT capture video and write it to a shared folder. 
Why? Interrupts. The machine could service the network card, or the 
capture card... but both at the same time caused things to go wrong 
(often resulting in W95 BSODing with obscure messages). This is what we 
get when any half-assed outfit can build a computer and call it 
"compatible" if Windows can run on it...


Apologies if there are any obvious typos. The netbook is warm, and I'm 
constantly pushing the cat off - some summer this is turning out to be.


Best wishes,

Rick.

-- 
Rick Murray, eeePC901 & ADSL WiFI'd into it, all ETLAs!
BBC B: DNFS, 2 x 5.25" floppies, EPROM prog, Acorn TTX
E01S FileStore, A3000/A5000/RiscPC/various PCs/blahblah...