80286 support? #41
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I have looked into it in the past for sure, and something that would be really neat to do some day. There is a decent amount of additional code needed for an AT/5170/286 BIOS including a complete hard drive BIOS, high-density floppy, AT keyboard interface, CMOS, protected mode code and a number of new This would be large enough that it would require being a fork to a project of its own, and I would like to take it on some day once I get a few more of these dependent issues done and out there. Since I don't have a timeline or a plan for when I can start on it, and it will become its own project I'm probably going to close this issue for now. However, knowing it's something that's asked for is really helpful to know and I really appreciate it! Thank you for the suggestion, |
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I know this is closed but I just want to add my thoughts. I'm working (slowly) towards 286 and AT support in VirtualXT. There is also the interesting case where you have XT machines with 286 CPUs. And since you know I like to sugest names for your future project I give you the sugestion of GLaTBIOS. ;) |
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My friend uses GLaBIOS with his IBM 5150, which he has a 10mhz 286
accelerator card, it seems to work quite well, he showed me it yesterday.
However, I dare say it would work even better if there were optimisations
for such setups (myself, I have a 6mhz 286 tulip card in my IBM XT), as
well as my 5162.
Cheers
Alistair
…On Wed, 10 Jan 2024, 21:38 Andreas T Jonsson, ***@***.***> wrote:
I know this is closed but I just want to add my thoughts.
I'm working (slowly) towards 286 and AT support in VirtualXT.
Just as you noted there is quote a lot on the system side that needs to
happen and probably this would have to be a fork if not to clobber the
current codebase.
There is also the interesting case where you have XT machines with 286
CPUs <https://en.wikipedia.org/wiki/Tandy_1000#1000_RLX>.
This is my first step along the way and I think the current BIOS would
work well with that.
And since you know I like to sugest names for your future project I give
you the sugestion of GLaTBIOS. ;)
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Thats cool! @640-KB Could we have GLaBIOS to be 286 aware during post? and perhaps dedicate another bit in the BDA where the V20 flag is stored? I think the best way to detect a 286 is to look what happens to the upper bits of the flag register when you push and pop it. (I think that is how the Wolf3D 286 detection code works if I remember correctly.) Although GLaBIOS is probably running fine a 286 there are some difference to a 8088/V20. Like the PUSH/POP SP instruction is slightly different. I'm working on some new validation hardware for the 286. (kind of like a 286 accelerator card for my emulator) |
Appreciate it - yes! I think it's a great idea, I only closed it since it would just need to be a forked project so wouldn't exist in this one (don't want an Issue hanging around here that would never be done on this project!). That's really cool to hear about the 286 and AT support coming. Do you plan to also implement the high density floppy controller as well? That's something I've been working on (very slowly) but there really aren't any emulators with debugging capability that support both 286 and a high density controller.
I've looked at Tandy support before and just that I haven't really pursued is that 1) Each model has a fairly different customized BIOS for its specific hardware 2) they tend to have somewhat proprietary (and under documented) hardware, such as keyboards, video, etc 3) I don't have one/don't have an accurate emulator that has any kind of debugger to make it easier to do. That said, since many of them share similar hardware to the PCjr it would open up the door for being able to create a PCjr target as well. Though the question is... which should we focus on... PCjr/Tandy or AT/286? :)
That's awesome! Just the right name will be a very important design decision for sure. :) |
Yes, I do have one of those as well (I think mine's an Orchid Tiny Turbo) and have used it with GLaBIOS and works great.
In truth, the current CPU type was really just meant to differentiate a V20 vs an 8088 from a functional perspective (don't allow V20 instructions to run on an 8088), but it does make sense to look at expanding it at some point (available code space willing). I do have some code to test for an 8086 vs 8088 but I've just never included it in the main repo due to code space limitations (it's actually a non-trivial number of bytes to do). And yeah, I did leave another bit or two reserved in the BDA byte to indicate other CPU types/capabilities (perhaps a bitfield where one bit indicates 16bit vs 8bit bus, another is NEC or Intel and another may be 186+ instructions available). I can look at the code space impact to add a 286 test (and code to display a different string) just to see what it would take. Would probably end up being a non-default build option so would only have a code impact for those who need it (since it could potential require sacrificing another feature in that build).
Yeah, since I already do some 186+ instructions now for V20 (
Oh cool... a 286 accelerator emulator option. That's neat! That will make testing this a lot easier too, since swapping the BIOS ROM on my 5160 that has that Orchid card is a big pain to do due to how tightly it sits in there. Also, I did just pick up an actual 5170 so that may help inspire more movement on this too. Okay - so I think I get the original request now a little bit better. Rather than talking about a full blown 5170 AT and beyond, we're looking for something that would enhance and/or target using a 286 CPU on an otherwise XT architecture. That makes sense and is reasonable. So I guess I should re-open this and put it on the list! Thx again for the ideas! 640KB |
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Currently I have been very lazy with the disk controller implementation. It is all done with a BIOS extension. :) (It is also because of harddrive support.)
I would go with AT. There simply is no opesource AT BIOS that I'm aware of and I think it is quite a common machine as well. It also defines an entire platform. Just like the PC/XT. Since I'm committed to supply an opensource BIOS with VirtualXT (it should be batteries included) there can never be any full AT support until there is a BIOS. :) |
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Thats cool!
I would have thought those cards had there onboard BIOS?
Afaik, no, they use the bios on the mainboard. There might be some kind of
shim somewhere, but it certainly starts the system using GLaBIOS.
…On Thu, 11 Jan 2024, 00:50 Andreas T Jonsson, ***@***.***> wrote:
GLaBIOS with his IBM 5150, which he has a 10mhz 286 accelerator card
Thats cool!
I would have thought those cards had there onboard BIOS?
@640-KB <https://github.com/640-KB> Could we have GLaBIOS to be 286 aware
during post? and perhaps dedicate another bit in the BDA where the V20 flag
is stored? I think the best way to detect a 286 is to look what happens to
the upper bits of the flag register when you push and pop it. (I think that
is how the Wolf3D 286 detection code works if I remember correctly.)
Although GLaBIOS is probably running fine a 286 there are some difference
to a 8088/V20. Like the PUSH/POP SP instruction is slightly different.
I'm working on some new validation hardware for the 286. (kind of like a
286 accelerator card for my emulator)
When that is up and running I would be able to test with the real thing. :)
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Perhaps you already know about the ATBIOS Kit? |
Oh, that's very interesting. I've never seen this before! This might just be very helpful to fill in some of the gaps with regards to a 286 BIOS. I will definitely give this a look over. Thanks so much for sharing it. |
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Added a PR draft for detecting a 286. |
Hi, I have an IBM 5162 XT/286 as well as 5170 / AT. Have you considered supporting the 286 at any point?
Cheers!
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