Uncreative Labs

Joined: 20 Nov 2004 Posts: 589 Location: Shandong, China

The Harris 25MHz 286 chips seem to be pretty common in China. I currently have a 20/25MHz 286 board with a 20MHz chip in place. I picked up a 25MHz version for a few dollars and plan to upgrade the board when I get back. However, I am really pissed off to find out that my Cyrix 287 chip is a fake, so currently I don't have an FPU that is fast enough to test with.

I also picked up a few QFP100 test sockets for 386SX chips. I am planning to solder one of these onto my 386SX motherboards that has the matching traces for it and pop in my recently acquired clock doubled TI SXLC2 50MHz chip. I'm not sure if it will work, because the 386SX board is from about 1990. Though, some guy at the CPU-Museum forum said he tried it and it worked.

I found two 387 FPUs. Another Intel 33MHz DX part, and a Cyrix Fasmath 40MHz part. I have yet to figure out what to do with them. I guess I'll use the Fasmath in my 386DX if the Blue Lightning upgrade doesn't work.

I also found a nifty Yamaha MPU-401 upgrade for next to nothing. I haven't bought it yet, but I think I will.

Finally, this is not an addition...but some guy in the Vintage Computer forum discovered that it is possible to get an SB16 (non vibra model) working in 8-bit XT slots. You can do this by setting the high DMA to 1. I'll have to give this a shot.

Joined: 22 Apr 2007 Posts: 20

Anonymous Coward wrote:

some guy at the CPU-Museum forum said he tried it and it worked.

What forum is that? URL?

Quote:

Finally, this is not an addition...but some guy in the Vintage Computer forum discovered that it is possible to get an SB16 (non vibra model) working in 8-bit XT slots. You can do this by setting the high DMA to 1. I'll have to give this a shot.

Yep, I saw that, I'll have to test that out as well Smile

Joined: 22 Apr 2007 Posts: 264 Location: Ohio/USA

How common are the 286-25 motherboards?

The 286 I have has a 20mhz CPU but the motherboard is 12/16Mhz only (with the FPU seetings show 8-12mhz). Headland chipset.

Joined: 20 Nov 2004 Posts: 589 Location: Shandong, China

Here is a discussion on cpu-museum.de (now deceased) that talks about the 386SX-->TI486SLXC2 chip.

http://www.cpu-museum.de/forum/viewtopic.php?t=1044

The 286 20MHz boards are pretty common. I've seen a few of them in the last couple of months. Most of those also had settings for the 25MHz chips as well. The 25MHz chips are also pretty common, but finding one sold with the motherboard is rare. However, I think the quality of the 20-25MHz boards is not as good as the 12-16MHz boards. You have to keep in mind these were made as late as 1993....many of them by crap companies like "PCChips". From what I hear the headland and C&T based 286 boards are the best. I'd try sticking with the board you have. Just pop a heatsink on the chipset or something.

My 20MHz 286 board is a PCChips and has C&T chipset. It seems to be decent, except that they cheaped out and gave me SIPP sockets instead of SIMM. I'll have to fix that....

Joined: 22 Apr 2007 Posts: 264 Location: Ohio/USA

I have (4) 30 pin SIMM slots, not sure if I can do 16MB on it. The CPU is a 20Mhz part, I just don't see a way of clocking it to 20.

Joined: 20 Nov 2004 Posts: 589 Location: Shandong, China

Is the CPU frequency being controlled by a metal can oscillator or some kind of IC?

Joined: 20 Nov 2004 Posts: 589 Location: Shandong, China

I've been doing some more rummaging, and got some good deals on the following items:

-Yamaha DB60XG MPU-401 daughter board
-Future Domain TMC850 SCSI card (8-bit truncated)
-ULSI 4c87DLC 40MHz, Cyrix Fasmath 83D87 33MHz
-Intel 487SX
-Plextor 12x/4x caddy CD-R SCSI

I'm sitting on a big mountain of neat crap, and I'm annoyed because I won't be able to test it all out until the end of the year.

Joined: 22 Apr 2007 Posts: 264 Location: Ohio/USA

So you snag some nice chips in China and then play with them back in the US?

Joined: 20 Nov 2004 Posts: 589 Location: Shandong, China

Yes, at least for now my things will reside in the US. I'm not sure where I'll end up later though. I think most of the chip sellers in China sell their wares on eBay, but the nice part about buying within China is that the shipping doesn't cost more than the actual product. Also, Taobao (auction site) doesn't charge sellers a fee so they can offer lower prices.

What's really unfortunate though is that I can't seem to find may EISA or VESA cards. I think there might be a lot of them sitting in junk piles, but the sellers don't know what to make of them so they don't even bother listing them.

Joined: 22 Apr 2007 Posts: 264 Location: Ohio/USA

There are VLB/EISA lots on ebay here every once in a while, but I think the quantity is going down since they don't fetch much.

I think quite a bit of gear that used to be plentiful has been recycled or kept in collections so there isn't that much left to be sold.

Are there computer shows in china where you have venders with huge boxes of sorted parts to look over?

Joined: 20 Nov 2004 Posts: 589 Location: Shandong, China

You know, I've been hoping to find a place with boxes to dig through, but no luck yet. There are quite a lot of electronics "malls", but I haven't seen any places with used junk yet. I've tried asking a few people about 286, 386 and 486 parts, but they just laugh at me. But, I figure these parts must be plentiful...because those Chinese sellers on eBay sure seem to have a good selection.

Joined: 20 Nov 2004 Posts: 589 Location: Shandong, China

Ah. I just stumbled upon the holy grail of XT class equipment. An Orchid Ramquest 8/16. It's an LIM4.0 EMS card that can take 32MB in 30-pin SIMM and works in both 8 and 16-bit ISA slots.

Joined: 22 Apr 2007 Posts: 264 Location: Ohio/USA

Anonymous Coward wrote:

Ah. I just stumbled upon the holy grail of XT class equipment. An Orchid Ramquest 8/16. It's an LIM4.0 EMS card that can take 32MB in 30-pin SIMM and works in both 8 and 16-bit ISA slots.

How much was it, and did it have any friends?

Joined: 20 Nov 2004 Posts: 589 Location: Shandong, China

Unfortunately, it didn't have any friends. I can't really put a price on it yet, because it came in a giant box of crap. The giant box of crap cost $10, though the shipping was much more than that. I am hoping I can have the seller remove some of the crap from the box to reduce the price of the shipping, and sell the other stuff to curb my losses. Though, I expect the seller will be reluctant to do so as they likely overcharged on the shipping to make more money. I figure I can maybe get $5 each for the memory cards, if I'm lucky.

Here's what came in the box:

AST Rampage 286
Unknown ISA memory board
2 AST SixPackPlus
Orchid Ramquest 8/16
Kodak Diconix 150 Plus Printer with Manual
2 5.25" adapter kit for 3.5" micro floppy disk drive
10 base T-Transceiver model 508A
Inmar EchoBox Model # X03902
internal SCSI hard disk installation guide
CentreCom MX20T twisted pair receiver
8mm Storage Cube data cartridge tapes 100 Flat Cable
13 FPY/CTRL
Programmed ROMS
EPROMS
LS/ MISC IC'S
Ethernet thin Coax Transceiver
ASST. BOX of RAM
Screen Kleen Removes dust before leaning your crt screen
Surge Protector
Macro Keyboard
Gender Changers
A box of various 41 microprocessors
5 R232 Null Modem
6 RS232 surge protector
5 no modem adapters
9 Gender Changer RS232

Joined: 22 Apr 2007 Posts: 264 Location: Ohio/USA

USA or from china?