Re: Extended Memory on PC/XT
Posted on 2023-01-28, 20:57
Errius wrote on 2023-01-28, 20:55: That's interesting, thanks. I always thought you needed a 386 for this. Probably thinking of EMM386.
Re: Extended Memory on PC/XT
Posted on 2023-01-28, 20:29
XMS on a 16-bit CPU? Don't you need 32-bit CPU for that? XMS itself is just a bunch of API calls for copying data to and from extended memory, abstracting away all the switches into protected mode and back. You can do this on a 286 if you have RAM above 1 MB. Part of the reason for XMS instead of …
Re: Extended Memory on PC/XT
Posted on 2023-01-28, 20:26
As UMB providers are a subset of XMS, providing UMBs for DOS=UMB is one legitimate use of XMS on an XT class machine.
Re: Dell Dimension 486SX 25 processor swap to 486DX. How do I change the bus speed?
Posted on 2023-01-11, 05:35
Are you sure? It's hard to see but there's an unpopulated Y1 and what appears to be the 14.31818 populated underneath. Might it use a clock generator chip? Any idea what the DIP switches are for?
Re: Help me choose compatible 30-pin SIMM memory for a 486
Posted on 2023-01-11, 00:37
Done!! PXL_20220712_004103973.MP.jpg That picture shows clearly that all 64MB is cached. If the BIOS offers "memory relocation", I recommend disabling it in this configuration. It might push a small amount of memory (like 128KB) over the 64MB limit, which might be uncached or (even worse, but …
Re: Which method for enabling the A20 line works in DOSBox?
Posted on 2022-10-10, 00:07
Abstracting away those differences is part of the job of XMS e.g. HIMEM.SYS. I think you should be checking whether an XMS provider is installed (which in DOSBOX should always be the case) and then use the XMS API calls to enable and disable A20. What are you trying to do, write a DOS extender?
Re: KLH / DTK 8088 motherboard ram
Posted on 2022-09-28, 19:23
You can't add any more onboard memory so you will have to use a card. You can either use EMS, in which a larger block of memory on the card is bank-switched in and out of a portion of the address space (such as D000 or E000) such as a Lo-Tech EMS card, or instead get a card that doesn't support EMS …
Re: Hard disk Type 47 parameters not adjustable? (Epson 286 BIOS)
Posted on 2022-09-26, 22:22
If you want it bad enough, you could change one of the entries in the FDPT in the BIOS ROM to match the CF card you want to use, and re-flash a BIOS chip. I am assuming this would involve hex editing the BIOS files directly? I'd presumably need to be able to identify where in the file those values …
Re: FTP client TSR for DOS?
Posted on 2022-09-26, 01:01
Um, isn't FTP considered insecure and obsolete? :confused: It's also very primitive. Browsers dropped support for it nearly a decade ago. If speed is not a problem, just use a nullmodem connection. Here are some DOS utilities that provide network drives via serial: https://www.vogons.org/viewtopic. …
Re: CMOS battery
Posted on 2022-09-25, 22:04
Kouwes wrote on 2022-09-25, 14:50: Ha! I actually plugged in the a: drive the wrong way. Not that it makes any difference, the system still says Drive not ready. Are there any settings in the BIOS about cache wait states? Or can you temporarily disable your 256K external cache?
Re: Hard disk Type 47 parameters not adjustable? (Epson 286 BIOS)
Posted on 2022-09-25, 18:16
If you want it bad enough, you could change one of the entries in the FDPT in the BIOS ROM to match the CF card you want to use, and re-flash a BIOS chip.
Re: CMOS battery
Posted on 2022-09-24, 20:59
JP3 is set at 1-2 closed, which means >25MHz. I didnt alter any jumper setting and the system ran wel when it was stored many years ago. Now I need to find another i/o card then. Does the CMOS setup have any settings about ISA bus divider though.At 50 MHz it should be 1/6. This would of course have …
Re: any 16-bit ISA MFM / Floppy combination cards that work with PC XT?
Posted on 2022-09-23, 07:20
If they were talking about it working, they were probably talking about letting the extra half of a 16-bit I/O card overhang, and only use the floppy/serial/parallel part disregarding the hard drive. Only the IDE hard drive part is actually 16 bits, so that works and is easier to find than an 8-bit …
Re: Windows 3.11 screensaver passwords
Posted on 2022-09-22, 21:38
VB4 is 32-bit, no? So it wouldn't work. The native development environment for something like this would be writing in C with Visual Studio 1.52c, or perhaps a contemporary Borland. Maybe you could get Open Watcom to work with it too. _Encrypt and _TwiddleBits are not exported functions, so you …
Re: Windows 3.11 screensaver passwords
Posted on 2022-09-21, 22:57
Take a look at the Windows 3.1 SDK specifically SCRNSAVE.H and SCRNSAVE.LIB. Each screensaver gets SCRNSAVE.LIB statically linked with it so the password stuff is duplicated in each one. It has symbols _TwiddleBits and _Encrypt. The password is all-uppercased, then each character is XORed with the …
Re: Debug an 8086 that won't power up
Posted on 2022-09-21, 02:07
Check OUT1 on the 8253 And you should see activity on the CS pins of the 8255, 8253, 8259, and 8237. The 8255 is one of the first chips to be accessed by the BIOS
Re: Debug an 8086 that won't power up
Posted on 2022-09-18, 21:28
What else can I try? I'm probably going to pull out a working 386 and try the cards on them to rule out any issue with the various interface cards. Suggest getting Ruud's diagnostic ROM from over at VCFed. It will generate POST codes, but also be aware that the modern (eBay) port 80h post card …
Re: CMOS battery
Posted on 2022-09-17, 21:30
Without knowing how much background you already have with these machines... 4 drives seems like a lot unless you're counting floppy drives. Perhaps this was a server. Are they IDE or SCSI? And of course you know they won't be autodetected on its own, unless this AMI BIOS is new enough to have an " …
Re: My 286 Mainboard build
Posted on 2022-09-17, 20:32
Excellent. I have a homebrew8088.com board, this seems in the same kind of spirit but interesting to see what you had to overcome via an FPGA chipset. I wish I could do that kind of stuff. How much different would it need to be for an 8086 or 386SX? Someday someone will take on a 486 VLB board... …
Re: ECS UM8810PAIO can't enter the BIOS
Posted on 2022-09-17, 04:14
Did you see this? Have to click through cert warning. https://www.dosreloaded.de/BIOS/Mainboards/FI … /UM8810PAIO.pdf
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