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jh1523
January 27th, 2009, 10:13 AM
Has anyone ever seen one of these? It's a 386DX mobo, which (as per the docs I found online) can come with either a 20, 25 or 33 MHz CPU. I don't know if the CPU is soldered or socketed though.

The reason I'm asking is because I found one of these online pretty cheap, but have no picture of it. It also comes with the proprietary memory card, so even a better deal.

dpatten
January 27th, 2009, 10:16 AM
Have you looked at TH99 to see if it has a schematic/pinout?

http://th99.dyndns.org/m/E-H/31579.htm

jh1523
January 27th, 2009, 10:26 AM
Yes I did (that's what I meant by "online docs" - well, that and http://bk0010.narod.ru/hardware_specs/m/) - but it isn't clear if the cpu is socketed or not, and also nothing specific in the part name to indicate the cpu speed.

My best guess is the cpu is probably socketed, and the mobo probably comes without any cpu - which makes it slightly less of a deal.

dpatten
January 27th, 2009, 02:24 PM
Based on the fact that the board was available in different speeds as well as the fact that it is a 386DX I would be shocked to find that the CPU was soldered on.

From the manufacturing standpoint, it is much simpler to make a one-size-fits-all motherboard than it is to make multiple versions of what is essentially the same item.

patscc
January 27th, 2009, 02:31 PM
If it's any help, on the drawing, the chip size looks about right for a socketed DX, judging by the FPU socket next to it. The qfpp DX is a tad smaller than the FPU socket.
patscc

jh1523
January 27th, 2009, 04:09 PM
Precisely my judgement. OTOH that means I'm not limited to Intel chips, and I can go hunting for a Cx486DRx2 or something. :)

Chuck(G)
January 27th, 2009, 04:13 PM
The Step 386 is socketed. Not as desirable as the early Everex (mostly SSI TTL) 386 mobos, but be careful --some of the early custom gate arrays have interesting "quirks". I don't know of the Everex is one of these, however.

jh1523
January 27th, 2009, 04:21 PM
Based on the fact that the board was available in different speeds as well as the fact that it is a 386DX I would be shocked to find that the CPU was soldered on.

From the manufacturing standpoint, it is much simpler to make a one-size-fits-all motherboard than it is to make multiple versions of what is essentially the same item.

Not necessarily. Many everex 386 boards have the CPU and base RAM on a CPU/memory card - with the CPU soldered on. And there is at least another everex 386 board that came with CPUs in 2 speed variants and they were soldered on: http://bk0010.narod.ru/hardware_specs/m/E-H/30520.htm

Chuck(G)
January 27th, 2009, 04:59 PM
Not necessarily. Many everex 386 boards have the CPU and base RAM on a CPU/memory card - with the CPU soldered on. And there is at least another everex 386 board that came with CPUs in 2 speed variants and they were soldered on: http://bk0010.narod.ru/hardware_specs/m/E-H/30520.htm

386SX chips, like 486SX chips were invariably soldered in--their raison d'etre being cheapness. 386DX boards, however, rarely had the CPU soldered in. The 18108 is a 386DX board.

Terry Yager
January 27th, 2009, 09:21 PM
From the manufacturing standpoint, it is much simpler to make a one-size-fits-all motherboard than it is to make multiple versions of what is essentially the same item.

From the marketing standpoint, it might be perceived to be more profitable to force the user to replace the entire mainboard in order to upgrade.

--T

dpatten
January 28th, 2009, 05:27 AM
Not necessarily. Many everex 386 boards have the CPU and base RAM on a CPU/memory card - with the CPU soldered on. And there is at least another everex 386 board that came with CPUs in 2 speed variants and they were soldered on: http://bk0010.narod.ru/hardware_specs/m/E-H/30520.htm


That's a 386SX. The situation is reversed with those. It's shocking to find one that ISN'T soldered on as the CPU is a 100 pin PQFP and is designed for surface mount soldering.

Of course there is always an exception, as my current hobby machine is a Zenith 386SX16 with the CPU in a strange little AMP socket.

Typically the only boards I've seen unsoldered 386SX chips on are 1988-89 vintage.


From the marketing standpoint, it might be perceived to be more profitable to force the user to replace the entire mainboard in order to upgrade.

--T

Yeah, but one would expect that primarily in low-end boards like the 386SX. The 386DX was pretty high-end at the time. If that were still the case we might be seeing lots of CoreQuad BGAs surface mounted sans 775LGA socket today, rather than low end stuff like the Celeron and Atom.


386SX chips, like 486SX chips were invariably soldered in--their raison d'etre being cheapness.

Are you sure that you aren't thinking of the i486SL? I've never seen a soldered in 486SX. The 486SL was a surface mount piece PQFP 132. Used in low end motherboards and laptops. I've seen 486SL chips soldered onto a carrier to be used in a socket on some low end motherboards.

Chuck(G)
January 28th, 2009, 09:29 AM
Are you sure that you aren't thinking of the i486SL? I've never seen a soldered in 486SX. The 486SL was a surface mount piece PQFP 132. Used in low end motherboards and laptops. I've seen 486SL chips soldered onto a carrier to be used in a socket on some low end motherboards.

Quite right--it was the 486SL. The 486SX was another sort of insanity on the part of Intel--sell a 486 with disabled NDP and then sell what amounts to a completely functional 486DX as a 487SX to put the onboard 486SX permanently to sleep.

Not to hijack the thread, but just a point of curiosity. Many 386DX boards allowed for installation of a Weitek numeric coprocessor in lieu of a 387. Does anyone own such a beast with the Weitek chip? I've never seen a 386DX board with the Weitek installed.

jh1523
January 28th, 2009, 10:17 AM
The Weitek 3167 was pretty high-end stuff itself, and IIRC costed several times more than a 386DX. I think it plugged straight into the 387 socket. Few people would afford or need them, unless they were using intensive CAD programs and such. Than's why they are pretty rare.

I have been occasionally searching the fleabay for a 3167, but have never seen one for sale. There are regularly 3170s and 3172s for sale since Sun apparently was more liberal with adding FPUs to its SparcStations. :)

Terry Yager
January 28th, 2009, 10:52 AM
IIRC, the Weitek socket is different from the 387, and some boards even have both (although only one or the other can be installed at a time). I personally have never seen one in the wild.

--T

patscc
January 29th, 2009, 07:09 PM
Digging through my parts bin(s), I dug up a Weitek 4167-33. Unfortunately, I don't have a motherboard for it. If anyone happens to stumble across one...
patscc