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Lode Runner for the PC with V20

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Great Hierophant

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I know that Lode Runner for the IBM PC doesn't work with a V20, and it supposedly can be patched. Apparently the problem is that the game uses the undocumented instruction POP CS, Opcode 0F, which only works on an 8088/8086 and was repurposed for the 80186 and more advanced CPUs. The V20 apparently doesn't implement it. It should be NOPed out or worked around. How can it be done? What hex string should I be looking for?

Does anyone know if Championship Lode Runner also has this issue?

Edit : The Retrograde Station DOS conversion will work just fine with an NEC V20 and an IBM PCjr. Presumably it was already patched when hacked. However, the game runs too fast.
 
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I tried the Lode Runner DOS conversion and it still ran too fast on an 8088-equipped PCjr. running with jrIDE. Either the game is extremely speed sensitive or just runs too fast on the jr.
 
The Lone Runner Retrograde Station booter runs at an appropriate speed off a floppy disk on a PCjr., perhaps a tad slow even. I think the game detects a PCjr. and calibrates the speed to run appropriately on it. However, it is limited to the slow first 128KB of RAM. When you run it off the fast sidecar RAM, it doesn't recalibrate itself (why should it when its a booter) and you get a game that runs too fast.

I tested the booter with the 8088, so I don't know if the booter, as cracked, will work with the V20. The odds are good though, but anyone care to test it? (I don't like to switch CPUs too often.)
 
I've tested my original Loderunner (Not cracked or converted version, dumped from original with copy protection.) on PCE (NEC V20 mode)
It works correctly.

Well, if your version doesn't run on NEC V20 PC, it must be bug of conversion or cracking for run on NEC V20.
 
fs5500 said:
I've tested my original Loderunner (Not cracked or converted version, dumped from original with copy protection.) on PCE (NEC V20 mode)
It works correctly.

Well, if your version doesn't run on NEC V20 PC, it must be bug of conversion or cracking for run on NEC V20.
Click to expand...

PCE is not a cycle-accurate emulator, so you can't trust this.

Great Hierophant said:
I tried the Lode Runner DOS conversion and it still ran too fast on an 8088-equipped PCjr. running with jrIDE. Either the game is extremely speed sensitive or just runs too fast on the jr.
Click to expand...

The game makes no attempt at adjusting for speed on faster systems. I see this booting the original disk on my 6300 (8MHz 8086, game is unplayable due to running too fast).

This is pretty common for games created before the IBM AT existed, for hopefully obvious reasons.
 
I have since tried the Lode Runner booter in an IBM PC, and the speed is noticeably faster than the PCjr. The speed adjustment option in the game is definitely more of a fine tune than a coarse tune.

By the way, the Retrograde Station Booter worked fine with an 8088 or V20 in the IBM PC. Either the version used was a later version that can accomodate a V20 or the hacker hacked around the issue. On the Tandy or PCjr., there was an annoying thing where the game would ask me every time I entered the menu or died if I wanted to use a joystick. My PC doesn't currently have a game adapter in it because I had to use the socketed 74LS244 from my AST Six Pak Plus for my IBM CGA New-to-Old Hack :(
 
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