Re: Floppy disk write sector vs implied seek?
Posted on 2021-06-13, 18:09
You would get a timeout due to the FDC not getting any data from the drive.
Re: Floppy disk write sector vs implied seek?
Posted on 2021-06-12, 23:21
If the disk is ejected during seeking, the seek would complete without issues (the drive's step motor is still going to move the head), but the read command is not going obtain any data from the drive, and therefore most likely time out, which would cause DOS to report "Not ready reading drive A:". …
Re: Floppy disk write sector vs implied seek?
Posted on 2021-06-12, 15:09
When does a write command perform implied seek? Before or after the data transfer to disk? Before. If implied seeks are enabled, when a READ SECTOR ID, READ TRACK, READ DATA, READ DELETED DATA, WRITE DATA, or WRITE DELETED DATA command is issued, the FDC compares the specified sector ID's cylinder …
Award Enhanced Keyboard Controller advertising sheet (needed for command list)
Posted on 2021-06-06, 21:39
Ralf Brown's I/O ports list has some keyboard controller commands marked as "Award" and then says this: Copy code to clipboard 1 (Award) Derived from Award's Enhanced KB controller advertising sheet. . But I can't seem to find this advertising sheet anywhere. Does anyone here happen to have this?
Re: DOSBox vs PCem vs 86Box which do you prefer?
Posted on 2021-05-26, 17:27
I also ended using 86box over PCEm for the better interface, but v17 brings optimizations that make it run much faster, and don't seem to be applied on current 86box builds. On my PC 86box can run POD on Windows 98 without CD music skipping on a P166MMX... PCEm v17 can do it on a P233MMX. Same with …
Re: How is a non-present slave detected on an ATA channel?
Posted on 2021-05-26, 17:22
Writes to register 6 are not ignored, at least for the drive select bit - that bit can always be written (but not read). If there's a slave without a master, and you select the slave, you're going to read noise from every port. When the master is present but slave is not, the master speaks for the …
Re: How is a non-present slave detected on an ATA channel?
Posted on 2021-05-16, 04:56
Yes, 0x00 is correct for a slave where the master is present, as per my tests on real hardware. When the master is absent, however, both return 0xff* (or 0x7f on boards with bit 7 pulldown, which most later boards do). * Actually, my tests showed noise being read rather than a stable floated bus …
Re: Wanted: full BIOS dumps from Intel 430TX/440*X motherboards
Posted on 2021-04-16, 22:52
The problem is that they are missing the boot block because the update is missing it. So a dump from an actual machine would be nice.
Re: (S)VGA 256-color shift and Chain 4
Posted on 2021-04-10, 22:17
I found your old posts about that stuff, and they match what I observe as well, and the OS/2 ET4000AX driver does the same thing - sets 256 color mode, without Chain 4, but expects to be in Chain 4 mode. On your end, I see that you simply patched the registers used, but there must be a better way to …
Re: (S)VGA 256-color shift and Chain 4
Posted on 2021-04-09, 22:20
But then why is it expecting to be in Chain 4 without Chain 4 being set? Edit: So then Shift 256 is OR'ed with Chain 4? That might be true but then wouldn't the Windows 95 boot screen and Wolfestein 3D both break since I have observed both of them using 256-color planar mode? Edit #2: Reading the …
Re: (S)VGA 256-color shift and Chain 4
Posted on 2021-04-08, 18:50
The OS/2 ET4000AX driver also writes to sequencer register 0E (which is entirely undocumented!), setting bit 1. The Windows 3.x ET3000AX driver sets bits 4 of attribute register 0x16. Edit: And I'm running the actual BIOS'es as well. What I see, with both of those drivers, is the card being put into …
(S)VGA 256-color shift and Chain 4
Posted on 2021-04-05, 05:37
On real hardware, does the the (S)VGA 256-color shift (GDC register 5 bit 6) force the video memory into Chain 4 mode regardless of sequencer register 4 bit 3? Or is that a Tseng-specific thing? Because I have two different Tseng drivers, the Windows 3.1 driver for the ET3000AX and the OS/2 "SVGA" …
Re: VGA difference of blacks?
Posted on 2021-04-01, 20:39
If SVGA monitors use the same specifications as (non-Japanese) NTSC, then blanking would be at 0%, while the active display (black to white) levels would be at 7.5% to 100%. But I'd look up actual (S)VGA documentation for that instead, perhals look up the voltage range and convert it to %, and then …
Re: Floptical drive support in Adaptec AHA-1542CF BIOS?
Posted on 2021-03-21, 02:43
- Cyrix200+: Would you be able to upload a dump of that AHA-1542CP v1.03 BIOS and microcode? All I can find anywhere is v1.02.
Re: Datasheets for Intel 420TX and 420ZX
Posted on 2020-12-19, 12:52
That only documents the southbridges, and not the northbridges.
Datasheets for Intel 420TX and 420ZX
Posted on 2020-12-19, 11:59
Does anyone have the datasheets for the Intel 420TX and 420ZX? All I can around is the first few pages from each, which is of not much use. So if anyone has the full datasheets of these, it would be greatly appreciated.
Re: Wanted: full BIOS dumps from Intel 430TX/440*X motherboards
Posted on 2020-11-24, 17:04
The structure of your images is strange - 512 kB with a lot of blank space in between.
Re: Wanted: full BIOS dumps from Intel 430TX/440*X motherboards
Posted on 2020-11-12, 17:47
- kepstin: The P10 version would be nice, as well as a redump of P3 since it's missing the first 128k.
Sound Blaster filters and CD Audio
Posted on 2020-10-19, 12:23
Does the Sound Blaster apply any of its filters (low-pass, treble, and bass - not all Sound Blaster versions have all of these) to the CD Audio it gets by cable from the drive? Edit: And what about OPL? Do those filters get applied to the OPL?
Re: PS/2 mouse on IBM PS/2 models 25-8086 and 30-8086
Posted on 2020-10-05, 19:18
So, if I understand correctly, on PS/2 Model 25-8086 and 30-8086, keyboard, mouse, and RTC alarm are all on IRQ 1, and IRQ 1 always issues INT 71h, whose BIOS handler then demultiplexes it to INT 70h, IRQ 1 INT (with base read from port 63h), and INT 73h. Looks like I'll need to add this special …
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