Common searches

Search results

Display options

Re: Live-booting a HDD-less Pentium4 laptop to backup floppy disks.

in DOS
Hiren's Boot CD (verison 10.6) is full of vintage DOS and Windows utils from the P4 era, it has a live Mini XP and a live mini Linux which are both loaded with useful programs. It's my go-to disc for any retro machine with a BIOS new enough to boot from CD-ROM. Easy enough to find a copy of Hiren's …

Re: VGA behavior when V. Display End >= V. Retrace Start

in Marvin \ Video
Just before the holiday season, I was playing around with improper VGA modes in an attempt to reload the CRTC start address multiple times per frame. I was doing my experiments on an old 286 with an integrated Paradise PVGA1A chipset. I was planning to do further work before writing it up, but Real …

Re: 8088 Interrupt delay timing

in PC Emulation
I thought it might be due to a microcode loop (the similar WAIT instruction is explicity documented as checking the /TEST pin every 5 clocks) but apparently not; reenigne's disassembly of the 8086 microcode page has this to say: There is no microcode for the segment override prefixes (CS:, SS:, DS: …

Re: Original IBM EGA card repair thread

in Marvin \ Video
Once you've checked the basics on the card (correct voltages, no shorts) a good next step would be to determine if the video BIOS on the card is readable / intact. My go-to method for this is to just load up DEBUG.EXE and use the "D C000:0" command to dump the first 128 bytes of the VBIOS. I usually …

Re: CGA "phantom" vsyncs: glitch-testing the 6845 CRTC

in Marvin \ Video
Very interesting! Inside the 6845 there will be a register or latch which holds the current value of R7, and this is fed to a comparator whose other input comes from the vertical counter. The comparator will be purely combinatorial logic. As the inputs to the comparator change, the various logic …

Re: targeting PC DOS 1.0 - how do you open files?

PC DOS 1.x is a very primitive (and simple) environment. It was a slightly more polished version of 86-DOS, which was originally designed (by Tim Paterson at SCP) to be a kinda-clone of CP/M which ran on the 8080/Z80 machines. It's just about possible to use a CP/M developer's manual to write a DOS …

Re: CRT randomly makes popping noise

in Marvin \ Video
It could just be a bit of dust/moisture from sitting in storage for a long time. I picked up a CRT that was in good working condition, great picture, but had obviously been in storage for a loooooong time. It made a lot of snapping/popping noises when first powered on, but over the next 5-10 hours …

Re: Some sofware to do fake EGA scanlines?

in Marvin \ Video
Also, it's just on the edge of possible to coax a standard VGA into producing a 640x600 mode (37.5khz horizontal and 60hz vertical) using the 28mhz dot clock. The horizontal timings are tight but a good CRT can handle it. If you can then output a frame where each of the 200 EGA lines is …

Re: Some sofware to do fake EGA scanlines?

in Marvin \ Video
You can disable the double-scanning bit even in modes that enable it by default. That seems to be just what that 'VERDE' program does if you enable the scanlines option. The vertical CRTC parameters have to be set accordingly, and for a full-screen picture you'll end up with a doubled (or nearly so …

Page 1 of 11