DOS Games Discussion

For those of you into extra percentage speed from older PC's, without over clocking the CPU, look to the ISA bus BIOS setting for "clk/3" or "clk/4" or "clk/5" etc. (some used slightly different labels). This is the ISA bus divider from the CPU speed. Happily, this proceedure doesn't cause more heat build-up in the CPU. However you may still need to provide reliable cooling to other vital areas of the cards and controler chips, so clear those dust bunnies.

Example: Normally 486-33, 66, 100 or 133 mhz CPU clk/4 = 8.25 mhz. Most ISA cards will take 20-40% more speed, so change the clk/4 to clk/3 = 11mhz. The 40, 80 or 120 mhz AMD's have it good: 40/4 = 10 mhz, not quite so big a jump but more stable. No ISA card I know of will get past 12-13 mhz reliably so consider it the limit. 386-25 clk/3 = 8.33 mhz, clk/2 = 12.5 mhz; right to the edge (but there may be a 2.5 setting). Thus the 286/386/486 crowd (especially the all ISA slot machines) will be very happy as the overall system can run 5-30% faster, verifiable by general peppiness, some improved frame rates on video clips, and some diag progs test scores (TroubleShooter and CheckIt come to mind). Remember to change back if any sign of errors or crashes result.

8088 PC's are a harder nut. Sometimes a jumper sets the bus speed but usually there's a clock crystal hardwired in. Some crystals were socketed and you can swap in a slightly faster one easily. Look for the square silver box(s) on your MB the size of a thumb nail. The speed is printed on them (14.xx or 8.xx or 33.3333, etc.). Keep the total increases to 20% for stability. Where to get them? Electronics stores and from old set scan video cards. EGA's and early VGA's had up to 5! There were faster 8088 chips out there too.

Note: You with VL-Bus and early PCI have to be careful as the jumpers on the MBoard could modify their bus clock even more. The ISA bus may work fine but the fast VL-Bus will freak, so consult your manuals, if you have 'em. You may have to set the fast bus for a slower CPU (as mine did) to get it all to happen. Still this tweek can be quite a boost for no cash.

in my bios there is no clk/3 or any of the others and i am running a 486

Too risky. I don't want to melt mine to increase framerate just to fly faster in Zeta Aqualae.

In this day and age its alot cheaper to have the correct cpu for the job at hand.

My 386/40 with cache plays the real old dos games at warp speed, anything that is newer is played on the p200mmx machine. I have my machines optimized with fast hd's and tons of memory so that speeds things up too. Since obsolete hardware is so cheap your better off buying the best video and sound card of the era to get the fastest and best sounding gameplay. Why overclock to get the most out of a oak vga card when you can get a tseng et4000 for a few bucks and its alot faster and supported by all games.

In 15 yrs of PC wrenching, I've never burned a board by overclocking the ISA bus. I have had freezes at 12-13mhz (thats +40-50%) or more, but 10 mhz (~25%) and 11 mhz (~33%) never caused a hickup.

That Tseng can still sing 25% faster.

Any game thats runs too slow on the 386 goes to the p200, so overclocking isnt needed. I probably should add a 486/66 or 100 machine just in case, but running out of room

Try and boost my pII 266mhz MMX. I cant.

Never buy the first intel chip of any new line they all suck and cant be upgraded (P60, P2-266, PPro 150, First P4, etc)

I didnt "buy" it really. It was in the computer I got at christmas.

Well somebody purchased it, they should have researched better.

It was $50 from one of my good friends.

Is it just that 266 is as fast as the jumpers allow the CPU to go? If so, my sympathies. Nice thing about changing the ISA bus multiplier is it DOESN'T change the CPU speed. Your CPU stays as cool as before. Therefore it's a main reason to recommend it, if you have the option.

Alternative: chill the CPU way down. (Many 3-486's went out the door often w/o any thermal assistance. EEK!) Every PC will run faster cold than warm/hot. There are several stratagies for this. Big heat sink/fan, thermal compound for good thermal transfer (+20-40%) to any heat sink, water cooled heat sink, refrigerated heat sink.... I recall a CPU at 0 degrees C is up to 25% faster than the same one at 60 C. I'm using the thermal paste + big heat sink + fans. No problems at all at 10% OC'd (this separate from the ISA bus increase entirely). Wish to give the refridge idea a shot soon and try for 3-40% OC'ing.

I figure your 266 has a typical heat sink and fan. First, blow out the dust bunnies. Now, is the heat sink bonded to the processor? (Bonded sinks don't use clips to hold them on.) If no, carefully remove the sink (don't break the holddown ears on the CPU socket!), and check for compound, if any. If it's dry or like clay, clean off any residue from the mating surfaces, add a fresh dab and spread it very even, thin and smooth over the whole mating area only (stay away from any electrical contacts visible). Too thick will actually insulate the CPU. Check that the CPU is still properly seated in it's socket. Seat the sink again and twist slightly a few times to get a good interface and feel for grit. Clip on the holddown clip and boot.

Note: Some of the sinks are hard to get on and off in the socketed (ZIF/PGA-like) PC's. The small die AMD's and Intels above ~500mhz need a lot of force and real care as the mating surface is only 1/2" square. Watch it!!

Daughter card (slot 1/slot A) CPU's need a little different care. Some are difficult to remove and are better off staying in the PC to work on, if there's room. Otherwise pull the card out after releasing the clips and then remove and service the heat sink as above. Keepa yo han's off the contacts!!!! Snap back in and boot.

At the very least the PC will run more stablely and last longer.

hmmmm overclocking is bad, I should scan a picture of "toasty" and put it on here...

Basically "toasty" is called that because when me and and one of my work collegues got delivered a computer about a fortnight ago with problems of not working suggested "power supply failure". We opened the case to find that chipset had exploded and melted everycard into it's slot and melted IDE cables that were attaching the HDD, Floppy and CD-ROM...
Basically we both made the decision it was overclocked with the chip not in properly...as I pulled out fragments which suggested it was in back to front!!

ooh, that's bad.... maybe i should overclock. but i found a big ferformance increase by turning off all the graphical stuff in windows xp off, by going to system in control panel, advanced tab, performance, adjust for best performance. also, check that on the advanced tab in the new window, that both checkboxes are set to "programs", not "background services".

meh, so what if i'm not l33t with a cool old system. i like my attitude problem. and i like the challenge of getting games to work.

Oz wrote:ooh, that's bad.... maybe i should overclock. but i found a big ferformance increase by turning off all the graphical stuff in windows xp off, by going to system in control panel, advanced tab, performance, adjust for best performance. also, check that on the advanced tab in the new window, that both checkboxes are set to "programs", not "background services".

meh, so what if i'm not l33t with a cool old system. i like my attitude problem. and i like the challenge of getting games to work.

I like tinkering with the hardware to get it so that it plays the games it was designed on perfectly (which is why I have too many machines). Collecting the hardware is almost as fun as playing the games to me. Installing a game to find out it wont play, doesnt sound correct, goes too fast/slow, crashes alot, etc isnt fun. I also feel that emulators are a last resort (for the same reasons listed above).

I overclocked my 300mhz and toasted it....



^kill bush-b|ackMagic^

man,shit yust happens,i ain' overlocking my 166mhz,too risky

It all depends on how you overclock the CPU. I had good look running p2-333's as 400's just by changing FSB from 66 to 100. I also overclocked old 486/133 amd to 160 33x4 FSB to 40x4. You run into problems when you overclock your memory bus/pci bus/isa bus or get too crazy with the cpu settings without propper cooling.


Its not worth the time to overclock anything slower then 1ghz because the chips are so cheap, overclocking new chips means your creating one hell of a heat source so reliability goes to hell.

SHOETAQUILLA wrote:Basically "toasty" is called that because when me and and one of my work collegues got delivered a computer about a fortnight ago with problems of not working suggested "power supply failure". We opened the case to find that chipset had exploded and melted everycard into it's slot and melted IDE cables that were attaching the HDD, Floppy and CD-ROM...
Basically we both made the decision it was overclocked with the chip not in properly...as I pulled out fragments which suggested it was in back to front!!

"Overclocked with the chip not in properly..."? CPU was "back to front"? I'd say that the result would be the same at even half the clock speed. You've got a dead short of high amperage for a long time through the bus on that crispy-critter, man. I'm rather surprised the P/S fuse didn't blow in the first 5 seconds. Don't blame that bonehead move on overclocking the CPU.

And remember, my original main point in this forum was NOT to O/C the CPU, but the ISA bus; a much much safer proceedure based on the fact that a large percentage of later 8088's went out the door at 10 mhz as standard for both CPU and ISA buses. Thus nearly 100% of all ISA cards made after 1985 were OK at that bus speed.