Using special machine types

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TheMechanist
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Using special machine types

Post by TheMechanist » Sat 19 May, 2018 9:47 pm

There are a lot of special machines emulated. But what is the advantage/disadvantage of using for example an AMI 286 clone vs. Epson PC AX or Dell System 200 ? Are the special systems more accurate emulated ? And if it matters, which one of the 286s models would you recommend ?

Zup
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Re: Using special machine types

Post by Zup » Sun 20 May, 2018 9:56 am

They have different BIOSes, chipsets, components and feelings.

Original IBM AT ran at 6 or 8 Mhz, but later machines (i.e.: Award 286 clone) could have 25 Mhz CPUs. Some chipsets were fasters than others or have some capabilities (EMM) fully integrated on BIOS. Also, the machines came with different components (i.e.: Amstrad PC2086 had a propietary keyboard and VGA included, IBM PS/1 had some kind of VGA and a strange unemulated hard disk controller). And some computers included parts (or the whole) OS on ROM (i.e.: Tandy Machines or that IBM PS/1).

Even having some kind of copyright/font/startihng messages on screen can make you feel like you're running your old computer.

A recommended machine? That IBM PS/1 is a strange machine that deserves some attention (but it needs the original hard disk contents and it lacks memory and performance). If you want to run a machine more accurate i'd use any machine rated at 12 or 16 Mhz, 2 Mb RAM and EGA video card. The overkill option could be a clone with 25 Mhz CPU, 4Mb and any 16 bit VGA card.

Or, if you had a specific machine back in time (i.e.: a Dell 200), i'd use that machine to remember old times.

NOTE: I think that differences between machines almost dissapeared when the 486 appeared... there are still some interesting (Compaq Deskpro) 386 machines, but there are almost no differences between brand and clone 486 computers.

NOTE 2: In some strange cases you'll need a set of specific components for a given task. Some OSs (i.e.: Xenix) may only support specific hard disk controllers, and I remember (but that's not 286 related) that BEOS didn't support many VGA and network adapters.

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TheMechanist
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Re: Using special machine types

Post by TheMechanist » Tue 22 May, 2018 12:23 pm

I see the point, but in most cases standard software won't see any difference?! .. how will the special machine types perform compared to the real machines? Can I expect that for example the Commodore PC30-III emulation will (nearly) have the same performance like the original machine?

EluanCM
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Re: Using special machine types

Post by EluanCM » Tue 22 May, 2018 7:37 pm

Between machines with similar features and performance, the difference will mostly be related to nostalgia and preservation. Sometimes there are bugs or quirks (real or from the emulation) that will make software work in one but not in another.

Zup
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Re: Using special machine types

Post by Zup » Wed 23 May, 2018 4:30 pm

PCem is not entirely cycle accurate, but the performance should be similar.

Assuming that your system can emulate your machines at 100% speed, you should note performance differences (i.e.: the IBM AT should be slower than a PC-30 III, because the former had a 6 or 8 Mhz but the latter shipped with a 12 Mhz 80286). A game should perform about at the same speed as in real machines (about, it is not cycle accurate).

I'm not sure about the different performances of chipsets, but I guess that memory and I/O access will be performed at the same speed in different chipsets (but note that you can put some WS to make it more accurate). The differences would be some abilities (i.e.: support of EMS). Also, keep in mind that hard drive access is at "host" speed (so programs will load almost instantly... opposed at early slow HDDs).

As I said, your main options should be either use your old machine (if it is emulated, to feel nostalgia) or build a "clone" machine with proper specs to ensure your software runs (a 286 with 16 or 20 Mhz and 2 Mb should be enough for all 286 software).

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leilei
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Re: Using special machine types

Post by leilei » Thu 24 May, 2018 1:15 pm

A lot of the special OEM machines PCem emulates also emulates their built-in video chipsets that sometimes doesn't have separate selectable emulation or have quirks/features of their own.

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