First post, by Marco
Hello all,
I have here quite a deep-tech question. Already know a lot about dos extender and its advantage of direct memory accesses and bypassing 640k barrier.
What is it about:
- With the introduction of DOS4GW all games using this protected mode came with higher HW requirements mainly 4MB of RAM
- This is valid also for games that are technically identical to their pre-successors using real time mode "engines". Mainly Sierra adventures. Why is that?
System setup:
- 386 SX / 25 with 2MB later on 4MB RAM
- Focus on games like Sierra Quest for Glory 3,4 Police Quest 4, Gabriel Knight
Examples:
- Sierras adventures using DOS4GW extender needed 4MB of RAM at minimum even providing the same graphic detail level then their pre successors.
- Even better: I was having a Sierra Online Demo CD which shows a Demo version of Quest for Glory 4 running in realtime mode without Dos4GW on my 386SX/25. Result: Flawless smooth as usual, no issues with 2MB of RAM. The final version of QfG4 were using the DOS4GW and was terribly slow and required 4MB RAM. Cost me 400DM back in the days to upgrade btw.
Also Larry 6 as an exceptional non dos 4gw Game ran fantastic.
Question:
Why is that? The 386SX supported 32Bit addressing instructions. Is it why it had to translate 32Bit instructions to its 16Bit bus which could let the double amount of CPU cycles per instruction (waitstates?). I never had a comparison with a 386DX/25 unfortunately but I could find some Forum remarks in the internet stating that 386sx performance Fall quite a lot behind their DX counterparts while using dos 4gw.
Thanks a lot
1) VLSI SCAMP 311 / 386SX25@30 / 16MB / CL-GD5434 / CT2830/ SCC-1&MT32 / Fast-SCSI AHA 1542CF + BlueSCSI v2/15k U320
2) SIS486 / 486DX/2 66(@80) / 32MB / TGUI9440 / LAPC-I