Overclocking the ISA bus isn’t very problematic with most VGA cards

But the hard drive/controller may flake out, especially if it’s scsi.

Sound is hit or miss , only way to know is to test the system for stability.

I’ve had my ISA bus as fast as 16mhz running stable but my sound card and modem would flake out.

Hi

HDD is Standard IDE. I have a IDE to SD card running DOS6.22 (Win 3.11 for that total pain in the a## feel) and a few old games such as lemmings and Monkey island. Thats all i have had time to do as its a 43*c (109.4*F) day here in South Aust. and the computer is in a tin shed!

I havent had a chance to adjust the jumpers to OC the bus yet just incase it toasts my data on the card.

Video cards that rely on the ISA clock for generating output signal will have a LOT of trouble, especially with LCDs. Acumos cards for example are terrible in this regard. Your mileage may vary.

ISA cards can usually handle 10 or 11Mhz. 12Mhz is where things can start getting iffy.

I would stick with 8.25 MHz. With that external cache (which is quite rare on a 386SX motherboard), you should already see a nice performance boost.
Maybe run some benchmarks and report back (Philscomputerlab has a DOS benchmark pack for 386 PC's that you can download).

Thanks for the advice guys. When it cools off here, as we are in the middle of a heat wave i will give some benchmark results...

Still dont know what that jumper does!

Hi All

Sorry it’s been a while but with Heat, Fire etc. over here I haven’t had much time to play with the system. I purchased a Co-Processor (387sx33) and fitted it to the mainboard. I re ran some testing with the Jumpers.

I have done some benchmarking with Different Combinations of CACHE and CO Processor.

I have some slightly interesting Results.... Only slightly though. It seems that for general gaming a Co-Processor does not actually aide much. There has been heated discussion on a few of the forums about this so I thought I’d come up with Proof of what I already knew!

I have determined that my mystery Jumper (JP7) has the only effect of making the system no boot when changed. I have tried this with different Cache and No Cache fitted, Co Pro installed and Not.

The system will not run well with the ISA bus overclocked.

Final Build Specifications are:

1. AMD AM386sx33 @33MHz
2. 16MB (4 x 4MB 60ns)
3. 64KB Cache (15ns)
4. 1MB ET4000ax
5. Creative SB16 (OPL 3)
6. 3com 3c905 LAN
7. xTIDE BOIS
8. 2GB SD in SDIDE
9. Generic CDROM
10. Microsoft Serial Mouse
11. Generic (IPEX) AT Keyboard

Its running very well, Stable and Fun!

Benchmarks Results:

How's the 386SX fare with DOS games except Doom? Decent ISA card is harder to get with performance minded like 1MB WD 90C31 or very late cirrus logic. I'm aware of Tnesg ET4000 cost on ebay is high but I had benched the Doom on a ISA ET4000 and a generic cached baby AT 386DX 25 but did not keep (was at store) while ago (Late summer 1994) and did ok but with some stuttering.

Secondly, how is your DOS games compatibility with ET4000AX?

I have a 386DX 33 SiS chip set Asus motherboard stashed away in closest. Yet to get is ISA video card.

Cheers,

pentiumspeed wrote on 2020-02-10, 00:45:

How's the 386SX fare with DOS games except Doom?

This depends very much on whether your system has cache or not. Without cache, it performs basically on par with a similarly clocked 286; my 386SX-25 without cache can deal with any game up until 1991 that I can throw at it. Starting with 1991 and onwards, certain games can become problematic. For example Civilization (1991) can become a real pain in larger maps and late game, Wing Commander II (1991) isn't a good experience, Dune II (1992) is slow, and Ultima Underworld (1992) is near impossible to play. It still plays most 1991-1992 games OK, though. 1993? Forget it.

Back in the '90 we didn't have the best 386DX mobos with fastest cache, RAM and VGAs we can buy today. Most people had cheap (and reliable) but only half-decent PCs and many games of the day were meant for such systems. So a pimped-out 386SX33 system, with cache to boot, should be reasonably fast.

The problem with games of that era is 16-bit code of the x86 family is horribly inefficient, and some apps might even run 8086 rather than 286 compatible code, so you aren't even using some goodies that newer CPUs had like rotates with immediate argument greater than 1 for example. 386 or not, it would be slow, and to add insult to injury the 386 had some instructions execute slower than 286 (that was the cost of having a new 32-bit CPU). So basically only 33 and 40 MHz 386SX CPUs would be faster than the top-of-the-line 25MHz 286 PCs.

The wider registers and new addressing modes of 386 were a huge performance boost but not available in 16-bit mode, and the games that required 32-bit CPUs typically assumed you'd have a DX25 at the very least so an SX system would again feel slow but for different reasons. That being said, Ultima Underworld can be playes on 386SX16 if you can live with Wolf3D-style graphics settings (no texturing on floors and ceilings). Note, back then 10fps was considered playable and in fact much faster systems can make the enemies way more difficult for example.

The mystery jumper is possibly for IRQ9 compatibility. It's something I've come across on a number of early 386 boards. Good luck with the build - a 386 was my first system as a kid and still my favourite selection of games.

Ultima Underworld is certainly not playable on a 386SX25 (no cache) using ANY settings unless your definition of playable is a stuttering slideshow..

appiah4 wrote on 2020-02-10, 11:43:

Ultima Underworld is certainly not playable on a 386SX25 (no cache) using ANY settings unless your definition of playable is a stuttering slideshow..

Just because it's not locked at 144fps doesn't mean it's unplayable. Sure it's a bit sluggish on Marty (and lowering detail level helps a lot) but by no means a "stuttering slideshow". Though granted, I haven't tested the PC version on anything slower than 386DX40 - I suppose having ISA bus between the CPU and graphics card could reduce performance a lot. I'll add that to the list of things to try sometime.

Deunan wrote on 2020-02-10, 13:31:

appiah4 wrote on 2020-02-10, 11:43:

Ultima Underworld is certainly not playable on a 386SX25 (no cache) using ANY settings unless your definition of playable is a stuttering slideshow..

Just because it's not locked at 144fps doesn't mean it's unplayable. Sure it's a bit sluggish on Marty (and lowering detail level helps a lot) but by no means a "stuttering slideshow". Though granted, I haven't tested the PC version on anything slower than 386DX40 - I suppose having ISA bus between the CPU and graphics card could reduce performance a lot. I'll add that to the list of things to try sometime.

Just a reminder that the 386SX was the bare minimum required CPU to run Ultima Underworld 1.

appiah4 wrote on 2020-02-10, 13:39:

Just a reminder that the 386SX was the bare minimum required CPU to run Ultima Underworld 1.

Well of course it was, the game used DOS-extender so a 32-bit CPU was required to even run at all. I tried to find some gameplay examples on YT but most are just using DOSBOX. There's one guy who used 386 at 25MHz (no clue if DX or SX) and says 'The 386 is almost a bit too slow for Ultima Underworld.' - almost being the key word here. Lower the details and it becomes more responsive (if also a bit uglier). I'd post a link but that person has no idea how to play and bumbles around in dark all the time, there's barely anything visible on the screen to judge the speed.

Again, it was the early '90 and games did look and run like that on many PCs. Let's not pretend everyone had a 486DX2 at the time UU launched.

I agree with the General Play. I built this to play some of the older games like they were played. No one I knew had top of the line 486's in the early 90's.. If you did then good for you but majority of people had the basics as they were so expensive (Here in Aust.)

I went overkill with the 16MB RAM and the ET4000ax VGA. 2 or 4MB system ram would have been period correct with a average trident or basic cirrus 512KB VGA.

The only reason i put in the Co-Processor was to show that it made almost no difference with period correct Games. Yes I could start Quake since it had a Co-Pro but why would you want to play that on this type of system? of cause if you didn’t have anything else then a Co-Pro may be the go but they were very expensive and almost no home user could justify the expense to get a game to run ~1fps!

It is quite happy with Duke and the rest for this era (1990-3)

It also clocks back to the Magic 8MHz (As Reported in Landmark and others) when De-Turbo. I can’t recall if it still enabled cache in that state.....

It defiantly worth a place in my retro line up so far...
386sx33
486DX 66, 32MB, Cirrus VBA 5428 (1MB)
P233MMX, 64MB, TNT2
PII 450MHz, 128MB, GeForce 2
PIII 1GHz, 1GB, GeForce 4
P4 2.4GHz, 2-4?GB, ATI 5? (In build)

I made a list with pics of nearly every game I played on my 386. 1995 was waaaay too long to be using that platform before I upgraded though. The fun part was replaying all the newer games to see how they were intended!

Just a reminder that the 386SX was the bare minimum required CPU to run Ultima Underworld 1.

it runs on 80186 16Mhz 😉 but indeed, its not fast.
also Next186 will run it (FPGA)

matze79 wrote on 2020-02-13, 08:13:

it runs on 80186 16Mhz 😉 but indeed, its not fast.
also Next186 will run it (FPGA)

You sure about it? I remember it required EMS memory to run, and so assumed it's that weird DOS extender that Origin used for their other games as well.
Next186 opencores.org page says "May run real mode 32bit 386 applications with a 32bit software extender (see EMU386)." - so the way I understand it, Next186 actually emulates 32-bit wide registers and new instruction encoding but not the full-fat paging and protection mechanism. That would be enough for many "flat-mode" apps to run.

EDIT: Well, it seems that EMU386 is a software 386 emulator. Which means it will cut the performance of the host platform to about 1/3, probably more like 1/4, when intercepting 386 code. On the other hand, the Next186 core executes most instructions in one clock cycle, has (small) internal cache and 32-bit external bus so can fetch new instructions twice as fast. On top of it it's capable of some 40-50 MHz operation on most common FPGAs, so that makes is more like 486 limited to 16-bit code. Let's say a 40MHz system, cut down to some 10MHz by EMU386 on 32-bit heavy code, that's still equivalent of about 16MHz non-cached 386DX speeds. Enough to run UU1.

So I guess I need to properly refresh my memory and try to run UU1 on a 286 system I have now to make sure - if it does run then the game engine is even more impressive than I thought.