stephen_usher wrote: ↑Thu Jan 27, 2022 6:48 pm
Here's the demo of the POST card. S1 isn't reset unfortunately, I've no idea what it does, maybe nothing on the ISA bus.
Hmm, interesting, I presume aside from the multi press reset to start, it's showing all good voltage wise?
Wonder if those QS8888's will work!
Collector of many retro things!
800XL and 65XE both with Ultimate1MB,VBXL/XE & PokeyMax, SIDE3, SDrive Max, 2x 1010 cassette, 2x 1050 one with Happy mod, 3x 2600 Jr, 7800 and Lynx II
Approx 20 STs, including a 520 STM, 520 STFMs, 3x Mega ST, MSTE & 2x 32 Mhz boosted STEs
Plus the rest, totalling around 50 machines including a QL, 3x BBC Model B, Electron, Spectrums, ZX81 etc...
Yep, all the voltages are fine and once the machine does reset properly it's bulletproof.
Soft resets work fine, so Ctrl-Alt-Del works as it should. It's only a hard reset which is a problem. I may hoik the CPU out and check what's happening on the RESET pin. According to the spec. it should stay high for at least 15 clock cycles to reset the CPU. For 33MHz that should be about half a microsecond, I think.
As for the chips.... You wait three weeks for one and then five come at once.
Intro retro computers since before they were retro...
ZX81->Spectrum->Memotech MTX->Sinclair QL->520STM->BBC Micro->TT030->PCs & Sun Workstations.
Added code to the MiNT kernel (still there the last time I checked) + put together MiNTOS.
Collection now with added Macs, Amigas, Suns and Acorns.
stephen_usher wrote: ↑Fri Jan 28, 2022 1:58 pm
Yep, all the voltages are fine and once the machine does reset properly it's bulletproof.
Cool.
stephen_usher wrote: ↑Fri Jan 28, 2022 1:58 pm
Soft resets work fine, so Ctrl-Alt-Del works as it should. It's only a hard reset which is a problem. I may hoik the CPU out and check what's happening on the RESET pin. According to the spec. it should stay high for at least 15 clock cycles to reset the CPU. For 33MHz that should be about half a microsecond, I think.
Does soft reset operate in a slightly different way to hard reset? Could the hard reset circuit have a failing IC?
stephen_usher wrote: ↑Fri Jan 28, 2022 1:58 pm
As for the chips.... You wait three weeks for one and then five come at once.
Bit like (data/address) buses then..........
Collector of many retro things!
800XL and 65XE both with Ultimate1MB,VBXL/XE & PokeyMax, SIDE3, SDrive Max, 2x 1010 cassette, 2x 1050 one with Happy mod, 3x 2600 Jr, 7800 and Lynx II
Approx 20 STs, including a 520 STM, 520 STFMs, 3x Mega ST, MSTE & 2x 32 Mhz boosted STEs
Plus the rest, totalling around 50 machines including a QL, 3x BBC Model B, Electron, Spectrums, ZX81 etc...
Apparently, on the 486 there are two reset pins, RESET for hard reset and SRESET for a soft reset. I'm guessing that Ctrl-Alt-Del uses the latter.
Intro retro computers since before they were retro...
ZX81->Spectrum->Memotech MTX->Sinclair QL->520STM->BBC Micro->TT030->PCs & Sun Workstations.
Added code to the MiNT kernel (still there the last time I checked) + put together MiNTOS.
Collection now with added Macs, Amigas, Suns and Acorns.
stephen_usher wrote: ↑Fri Jan 28, 2022 2:24 pm
Apparently, on the 486 there are two reset pins, RESET for hard reset and SRESET for a soft reset. I'm guessing that Ctrl-Alt-Del uses the latter.
Oh, that's interesting. Wonder what the differences are then.
Collector of many retro things!
800XL and 65XE both with Ultimate1MB,VBXL/XE & PokeyMax, SIDE3, SDrive Max, 2x 1010 cassette, 2x 1050 one with Happy mod, 3x 2600 Jr, 7800 and Lynx II
Approx 20 STs, including a 520 STM, 520 STFMs, 3x Mega ST, MSTE & 2x 32 Mhz boosted STEs
Plus the rest, totalling around 50 machines including a QL, 3x BBC Model B, Electron, Spectrums, ZX81 etc...
Intro retro computers since before they were retro...
ZX81->Spectrum->Memotech MTX->Sinclair QL->520STM->BBC Micro->TT030->PCs & Sun Workstations.
Added code to the MiNT kernel (still there the last time I checked) + put together MiNTOS.
Collection now with added Macs, Amigas, Suns and Acorns.
stephen_usher wrote: ↑Fri Jan 28, 2022 2:41 pm
486-reset.png
486-sreset.png
So then the majority of the reset remains the same with the exception of that register?
Collector of many retro things!
800XL and 65XE both with Ultimate1MB,VBXL/XE & PokeyMax, SIDE3, SDrive Max, 2x 1010 cassette, 2x 1050 one with Happy mod, 3x 2600 Jr, 7800 and Lynx II
Approx 20 STs, including a 520 STM, 520 STFMs, 3x Mega ST, MSTE & 2x 32 Mhz boosted STEs
Plus the rest, totalling around 50 machines including a QL, 3x BBC Model B, Electron, Spectrums, ZX81 etc...
Looks that way. I would have suggested putting SRESET first in the sheet and had RESET as being, "As SRESET but also clears xxxx register."
Intro retro computers since before they were retro...
ZX81->Spectrum->Memotech MTX->Sinclair QL->520STM->BBC Micro->TT030->PCs & Sun Workstations.
Added code to the MiNT kernel (still there the last time I checked) + put together MiNTOS.
Collection now with added Macs, Amigas, Suns and Acorns.
stephen_usher wrote: ↑Fri Jan 28, 2022 3:00 pm
Looks that way. I would have suggested putting SRESET first in the sheet and had RESET as being, "As SRESET but also clears xxxx register."
Yeah, would have made more sense.
Collector of many retro things!
800XL and 65XE both with Ultimate1MB,VBXL/XE & PokeyMax, SIDE3, SDrive Max, 2x 1010 cassette, 2x 1050 one with Happy mod, 3x 2600 Jr, 7800 and Lynx II
Approx 20 STs, including a 520 STM, 520 STFMs, 3x Mega ST, MSTE & 2x 32 Mhz boosted STEs
Plus the rest, totalling around 50 machines including a QL, 3x BBC Model B, Electron, Spectrums, ZX81 etc...
I've got the chips home and suspiciously they all have the same date code, but different markings on the underside. The writing isn't quite the same as the original chip either.
The pins show that the chips have been pulled from sockets.
Well, there's one way of finding out if they work...
Intro retro computers since before they were retro...
ZX81->Spectrum->Memotech MTX->Sinclair QL->520STM->BBC Micro->TT030->PCs & Sun Workstations.
Added code to the MiNT kernel (still there the last time I checked) + put together MiNTOS.
Collection now with added Macs, Amigas, Suns and Acorns.