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Replacing the V20 back with the original 8088 was a good test step, for sure. I'm starting to think you have a different hardware problem around the timer circuitry, or something causing an extra wait state. Landmark 2.0's "CPU Clock" should show the actual frequency your CPU is running at...

What key combo are you trying? Ctrl-Alt-Plus and Ctrl-Alt-Minus (on the numeric keypad)? If the manual gives you that info, then I would agree with Ruud here - it could be a weird custom BIOS that doesn't have that functionality. Just another [far out there] thought regarding the keyboard - is...

Love the list provided by @cj7hawk! I got my hands on a very early Osborne 1 last year, serial no. 002369, and did some repairs to it before passing it on. Some of my write-up here might be useful.

Great job @Pickelhaube808 ! I was going to add that negative H / V signals don't really mean negative voltage, just that the + means "high positive" and - means "low positive". At least that's my limited understanding so feel free to correct!

I would caution against using any old PSU. The last thing you need is an aging power supply that creates a ripple or overvoltage in any of the DC output lines going to your motherboard. It may not be in keeping with a retro PC to replace it with a modern supply but you will sleep better at...

Yeah, I'm no expert (maybe reach out to Dave Dunfield since he developed those utilities), but it's the floppy disk controller chip that determines the ability here, so you're on the right track by disabling your onboard FDC via the BIOS and putting in something like a Goldstar Prime or Prime 2...

@bitfixer , My Osborne 1 had only the single-sided capacity drives, and I successfully used the disk image called o1cpms.imd (different filename to yours). As per my article, I ran Dave's TESTFDC utility first which tests your floppy disk controller at various speeds to see if your PC can cope...

@WimWalther, got any pics? sounds interesting!

Thanks @agentb , I will give that a go and update the review if I have any luck.

For what it's worth, I recently did an article on a bunch of these CGA cards with the VDL chip. I still haven't managed to get composite out from the 2-pin header, so if anyone has discovered how I'd be interested!

I personally highly rate the earlier Cirrus Logic cards such as those with the CL-GD510/520 chipset. These are often found in 8-bit ISA form as well as 16-bit. Many have both the 15-pin VGA/SVGA analogue monitor port as well as the older 9-pin digital out for Hercules, CGA and EGA. I used to...

Back in April I was working to get a donated Osborne 1 back to life. As part of my findings, I came across the excellent site of Dave Dunfield. His page here has single-density boot images for the Osborne 1: http://dunfield.classiccmp.org/img42841/system.htm

Good info @rittwage, thanks!

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Thanks @Timo W. and @C128 Guy, I think it's less about the fact it's in a ceramic package, and more (a) the production date of week 20, 1982, and (b) the code on the underside of the chip. Timo, since your chip is out, can you send a pic of the underside also?

Hi everyone, One of my viewers at RetroIsle.com has asked me to try and find out any information about a possible engineering prototype SID he has acquired. He writes: "I am a Commodore collector and have either an engineering prototype C64 or what I believe is a super early consumer sale...

He heh, Hey, @dr.zeissler, another thought to your problem is to get an ISA riser card to get more available slots, though this presents a challenge if you're trying to keep your computer in its case.

I have one of these detachable thumb ball mice too, but on a Toshiba T4800CT (a 486DX4-75) - takes a bit of getting used to!

Thanks @Caluser2000, it's actually 'zero'-'E', as that first page includes games beginning with a number ;)

For what it's worth, Viglen Computers were a huge PC manufacturer in the early PC-compatible era - competing directly with Compaq (in the desktop market) and AST. You guys in the US had CompuAdd and Gateway 2000 (which we in the UK had also), but Viglen had a much larger market share in the...