vDos Exception

[chrisr]

Sorry, very new to vDos and still trying this out.

The DOS software works fine under Windows 98.

Wondering if anybody has had this issue and worked out what caused it?

And is there anyway to avoid this?

[Jos]

To address XMS memory, the Phar Lap manager uses virtual memory paging: Virtual addresses are translated by the CPU to physical addresses. This translation costs time, a 32 bit virtual address consists of a 10 bit page and frame entry number, and a 12 bit offset in the latter. To speedup this translation, the CPU uses a TLB (Translation Lookaside Buffer), containing a portion of all virtual addresses. With an emulated CPU searching and maintaining such a cache actually costs more time than the translation itself. So vDos instead uses a large TLB containing all virtual addresses it anticipates.

Could be the vDos TLB is too small as the exception suggests, perhaps there are extraordinary many page entries with little linked frame entries. But the virtual address could also be incorrect. Can you submit a minimal setup of your program, just that required to start the program and invoke the exception?

Jos

[chrisr]

Jos,

Thanks for your reply.

The software is very simple and comprises a single executable file. I have attached two versions of the program:

Attachment Deleted

1993 version runs OK [need to rename back to PIGLET.EXE]. 2001 version gives the error.

But because of some small but significant changes, plus the licensing personalisation, I need to use the 2001 version. Both run OK in my VMware Windows 98 virtual machine, but VMware has a big hit on resources and I struggle to use on my laptop.

Thanks for your help.

[Jos]

It was indeed a shortage of TLB entries. I changed the formula that determines the array size to support 256 more entries, and PIGLET.EXE started like PIGLET1993.EXE.
I’ll send you a modified vDos.exe coming weekend by wetransfer.

Jos

[chrisr]

Jos,

Super. Thanks for your help. vDos is great to keep some of my old software running.