PDA

View Full Version : Pros and Cons of 386SX-25 Upgrade from a 286-12?



ScanDisk
August 26th, 2017, 12:22 PM
My Pack-Mate III works very well now with it's 4mb of RAM, and it's Sound Blaster 16 (can't use it in Windows 3.1 standard mode, but works just fine in DOS, even with software that think's it's an SB PRO).

I know the weakest point in my system is the processor itself.

I am thinking of upgrading to a 386, so I could run Windows 3.1 in 386 enhanced mode which would allow me to install the SB16 drivers and have audio within Windows, plus lots of software seems to require at least a 386, and obviously things would run faster overall.

I think it should be possible as these are both 16-bit processors, and the only limit should be the bus speed.

My BIOS does say 80286 on the boot screen, so I don't know if it would say 80386 if I swapped it with a 386, and also the motherboard is a Packard Bell 286X, so it's probably designed specifically for a 286.

I'm new to working with machines as old as these, so would I be able to upgrade to a 386SX-25 like this - http://www.ebay.ca/itm/1pc-INTEL-NG80386SX25-IC-MPU-32-BIT-5V-25MHZ-QFP-100-new-original-/111603310298?hash=item19fc135eda:g:33IAAOSwqu9U5wX F ? Or am I stuck with my 286-12?

krebizfan
August 26th, 2017, 12:40 PM
You would need a different motherboard and chipset to use a 386SX chip directly, the chips were incompatible. There were adapters of various types that would permit installing a 386SX in a 286 but those are scarce and very expensive. Far better and lots cheaper on the whole to get a full 386DX with a good motherboard.

Most 386SX motherboards lack provision for cache so it will be vastly slower than the same clock speed 386DX. Cache contributes about 20% to performance. The 16-bit memory bus causes a decline of another 10%. Thus, the 386SX-25 will perform about the same as a 386DX-16.

ScanDisk
August 26th, 2017, 12:55 PM
You would need a different motherboard and chipset to use a 386SX chip directly, the chips were incompatible. There were adapters of various types that would permit installing a 386SX in a 286 but those are scarce and very expensive. Far better and lots cheaper on the whole to get a full 386DX with a good motherboard.

Most 386SX motherboards lack provision for cache so it will be vastly slower than the same clock speed 386DX. Cache contributes about 20% to performance. The 16-bit memory bus causes a decline of another 10%. Thus, the 386SX-25 will perform about the same as a 386DX-16.

Thanks.

I have seen those adapter cards, and they cost more than the $110 that I paid for the pack-mate, the monitor, mouse, keyboard, DOS 3.3, and User Manual.

So it seems, since I do like this computer and have grown attached to it, I am stuck with the 286.

But maybe I could get a faster 286? Like a 286 at 20Mhz? It wouldn't allow Windows 3.1 in 386 enhanced mode, but it would run faster I woudld guess.

krebizfan
August 26th, 2017, 01:16 PM
Tricky question. Yes, there were faster 286s but the system may not work at higher speeds. It was common for a 286-12 to fix the ISA bus at 2/3 the speed of the CPU. That gave an 8 MHz bus with a 12 MHz CPU. Cheap and stable. Increase oscillator frequency to work with the 20 MHz CPU and the bus is going to run at 14 MHz which will drive many expansion cards crazy.

ScanDisk
August 26th, 2017, 01:24 PM
Tricky question. Yes, there were faster 286s but the system may not work at higher speeds. It was common for a 286-12 to fix the ISA bus at 2/3 the speed of the CPU. That gave an 8 MHz bus with a 12 MHz CPU. Cheap and stable. Increase oscillator frequency to work with the 20 MHz CPU and the bus is going to run at 14 MHz which will drive many expansion cards crazy.

Okay, so it looks like I will be keeping the same processor.

I guess I'll just need to use it as people from that time did,

or like a teen who got a hand-me-down computer form his parents in the early 90's or something. :P

Wolfenstien 3D runs fine with 4mb of RAM, though I need to make the game screen small.

Caluser2000
August 26th, 2017, 01:44 PM
Okay, so it looks like I will be keeping the same processor.

I guess I'll just need to use it as people from that time did,

or like a teen who got a hand-me-down computer form his parents in the early 90's or something. :P

Wolfenstien 3D runs fine with 4mb of RAM, though I need to make the game screen small. Yeah accept the 286 for what it is. A 16 bit processor that can run a lot of Dos programs ;)

Stone
August 26th, 2017, 02:29 PM
Okay, so it looks like I will be keeping the same processor.

I guess I'll just need to use it as people from that time did,

or like a teen who got a hand-me-down computer form his parents in the early 90's or something. :P

Wolfenstien 3D runs fine with 4mb of RAM, though I need to make the game screen small.I found that I really liked Wolfenstein 3D on my 386-40 but anything less was just fair.

Why would you want to play a game on a substandard machine when you've got something that can play it full-on?

Caluser2000
August 26th, 2017, 02:55 PM
Half the fun of setting up a system is seeing what will run and what wont.

Stone
August 26th, 2017, 04:04 PM
Half the fun of setting up a system is seeing what will run and what wont.Just barely running isn't what I consider fun.

Besides, five minutes of very simple reading and you'll know what runs well and what doesn't. It's not rocket science, at least not for some of us. Reinventing the wheel is not something I'm prone to spend time on. :-)

ScanDisk
August 26th, 2017, 05:03 PM
I would love to upgrade this, but the only way it seems it can be done is with the accelerator boards, and those are way too expensive to justify.

PeterNC
August 27th, 2017, 04:24 AM
Keep an eye out for a 386 / 486 Pack-Mate on eBay / Craigslist / Goodwill / Bonanza / VCFED and so on. :)