OpenEuphoria

SVGA Test and OSes

• Posted by Mathew Hounsell <mat.hounsell at MAILEXCITE.COM> May 18, 1998
• 642 views

[SVGA TEST]
I think a DOS interrupt has been used to test if the SVGA modes exist. I think,
 Dave Cuny's machine it keeps crashing. I have some ideas.
On a machine without that interrupt calling that interrupt may crash it so I
 came up with the following Pseudo Code

BEGIN
        Save Registers
        Disable Interrupts
        Read from mem the vector for the SVGA Interrupt (0000h:(IntNumber*4))
        Enable Interrupts
        IF Vector != NULL THEN
                IF Vector != Error Interrupts Address THEN
                        Try the interrupt.
                END IF
        END IF
END

An unused interrupt is either set to NULL (INT 00h : CPU GENERATE - DIVIDE ERROR
 ) or re-vectored to the Error Handling Interrupt (INT 24h, I think). This may
 be what's hanging Dave's system. Unfortunately there is no direct way to
 [dis]enable interrupts in Euphoria, unless get_vector does it automatically. If
 it doesn't then a com program might be called for. If get_vector disables the
 re-enables interrupt the could then become

---<untested code>---
function check_interrupt( integer num )
sequence vector
integer val

        val = 1
        if num > #FF then
                vector = get_vector( num )
                if vector[1] = 0 then
                        if vector[2] = 0 then -- NULL Vector
                                val = 0
elsif vector[2] = #24*4 then -- DOS ERROR HANDLING
                        Vector (???)
                                val = 0
                        end if
                end if
        else
                val = 0 -- Bad Interrupt Number
        end if
        return val
end function
---<end>---

Also according to one lot of information I have INT 4F (SVGA INT) is also the
 SCSI Controller INT perhaps there is a conflict or your trying to ask the SCSI
 controller to do SVGA things. This should be done all the time, so I suggest a
 setup program.

[OSes]
I reinstalled Caldera Open DOS, ran several Euphoria programs and every thing
 seemed to work fine. I didn't use any network support though as I don't have a
 network.
Oh on the subject of OSes, if you want a simple OS, try the QNX OS Demo, it
 fit's on a floppy. Including, HTML 3 Web-Browser with Modem & TCP/IP suppport
 and Text Editor. It however doesn't have disk support, so you can't save, but
 just to surf the web it's great as you just have to keep it on a disk, oh and
 it can print as well, I think. It has a GUI for those who like that sort of
 thing.

---
Sincerely,
Mathew Hounsell
Mat.Hounsell at mailexcite.com



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