

Those disks sizes are good for anything up to 286 or at much 386. The list of predefined HDDs is not something that PCem invented, but the default table of compatible disks on the initial PC BIOS. PCem pretends to emulate what real hardware was supposed to do, and the use of real BIOSes of those machines also imposes some of these limitations. At least, this is what VHD does, but I find it all a bit murky. It is simply gated in the settings at creation time.Īgain, I'm no expert but from my reading around, I THINK for large disks, SPT is supposed to be 255 (and not any value in-between 63 and 255). It's hard-coded in the settings code to scream at you when you try over 63 SPT.Īlthough, as far as I can tell, and I know very little about this sort of thing, but I don't think there's any inherent limitation in the emulation itself. The limit for heads that's 16, it's SPT that is increased to 255 in VHD. I think the latest machines that PCem emulates support 255 heads, but I don't think any of the older (pre 430VX) BIOS's do.ĭo you have any exmaple to try? Cause all the ones I tested so far scream at me when I go over 16Īrrghh, sorry, it's been a while, I misspoke. This can make mapping between pcem's CHS geometry and VHD's geometry rather annoying, as ideally one has to find a disk size that matches both 63*16*x AND 63*255*x

This is an issue I've run into with VHD support, as it only supports up to 65535 cylinders, so for large hard disks, you are supposed to set heads to 255. The largest heads and sectors-per-track supported by PCem is 16 and 63 respectively, so for large hard disks, you have to use the cylinders to get the final size.

How exactly can I achieve this with the limitations above? What is the effective largest size we can configure with the emulator?įor now I am wanting to build a 4886 machine and a Pentium 233MMX one.ĮDIT: Was just re-reading the changelog and notice that for v14 even it says: If the above is correct, does that mean that the largest possible sizes would be with those two at 16 and 63 respectively, and we can only play with the cylinders number? Within the emulator, there seems to be a fixed arbitrary limit of 16 for heads and 63 for sectors. I have found several tutorials and general info sites, with tables with the CHS parameters for different sizes, however, some of them have values that do not seem to be allowed in PCem. The only thing I am confused about (for now), is regarding the creation of HDD images.

Hi folks, PCem noob here, I more or less got the hand of the general workings and how to put together a machine.
