Tag Archives: bug

Electronics and Computers, Macintosh, Posts

Basilisk II Emulator Floating Point Bug

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Basilisk II Emulator Floating Point Bug

I’m not sure if it is just my specific installation, but I’ve noticed an issue in Basilisk II regarding floating point values, where the value displayed is incorrect. This has caused me problems a few times, but this evening, I worked out a partial solution.

The issue seems to be in the FPU emulation itself. I use a IIci ROM in my installation. I found that if I set the CPU to either a full 68040 or a 68030 + FPU, floating point values were wildly wrong. I then found that the vanilla “SANE” routines work, so if you set the emulator to 68030 (without an FPU) everything works just fine.

This will slightly reduce software compatibility (although I doubt software that required the FPU would function correctly with the completely incorrect values I was getting), but will mean that software that doesn’t require a hardware FPU will run correctly.

Update – dougg3 has noticed that the issue happens when he uses the IIci ROM, but not if he uses a later (LC 630) ROM.

I have made a small testing tool, which is available for download here :

https://github.com/Phipli/FPUCheckhttps://github.com/Phipli/FPUCheck

Electronics and Computers, Mac OS 8, Mac OS 9, Macintosh, Posts, System 7

Virtual Memory Not Working on Classic Mac OS

Virtual Memory Not Working on Classic Mac OS

When you have a lot of physical RAM installed in your Mac OS Classic era Macintosh, sometimes you might find that it isn’t possible to enable Virtual Memory. This can be a problem as some software, especially games, refuses to launch if you don’t have Virtual Memory enabled.

In this situation, one trick can be to create a large RAM disk using the Memory control panel. This consumes a load of the available System memory and magically makes the Virtual Memory options re-appear.

Once you’ve finished with the software that requires Virtual Memory, delete the contents of the RAM disk (if there is any) – fastest way is to just to select the icon on the desktop and then Erase from the Special menu, then turn off RAM Disk in the Memory control Panel.

Electronics and Computers, Macintosh, Posts

Erratic Mouse or Touchpad in Classic Mac OS

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Erratic Mouse or Touchpad in Classic Mac OS

The Problem

Very occasionally I find that I need to use a modern pointing device on my retro beige macs through a PCI USB card. An oddity I’ve noticed is that as soon as I touch one of my modern Logitech touchpads, the cursor starts continuously moving to the right. With mice, the behavior is similar, but a little more erratic.

The Solution

Thankfully, there is an easy answer. A little shareware Control Panel called USB Overdrive. This utility is mainly for configuring joysticks and gamepads, but it also offers controls for mice and keyboards. I’ve found that by configuring the mouse settings within USB Overdrive, it fixes the “go to the right” issue with my Logitech devices. I’m uncertain whether the issue exists with other brand’s pointing devices as most of my modern peripherals are Logitech.

USB Overdrive is shareware and can be downloaded from the following site :

https://macintoshgarden.org/apps/usb-overdrive-14

Or locally from here in case the path changes (please use and support Macintosh Garden – remember to contribute any obsolete software you might have on disk which is not already there).

Setup

Once you have installed USB Overdrive on you Mac OS 9.2.2 or older, USB compatible mac, go to the control panel and select an option other than the default “System” from the “Speed” drop down menu. This is all that is needed to fix the bug.

USB Overdrive Screenshot
USB Overdrive Screenshot – Image from Macintosh Garden

Notes

If you’re having trouble getting a USB PCI card working, try re-installing your operating system while the card is installed. By default the system installers do not include the required USB drivers unless they find the hardware. A fresh install can massively help with troubleshooting. USB got more reliable with time I believe it was first introduced for Mac OS 8.1 (for the iMac), but functions progressively better in newer versions up to 9.2.2.

While most USB PCI cards “just work” in beige macs, it is widely reported that the most stable and reliable cards are those that use the OPTi chipset and have two USB ports. This is the same chipset as was used in Macs with built in USB and so is the best supported.