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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

RiP2
June 5th, 2019, 11:19 PM
I have this motherboard too but some questions: :confused:

1. What kind of external CMOS battery should I use for it? (Red arrows)
2. What's the Instep socket? (Magenta arrow)
3. What's the 512K jumper? (Yellow arrow)
4. Any BIOS upgrade for it?
5. Possible to put a faster CPU >33MHz on it?

https://stason.org/TULARC/pc/motherboards/E/EVEREX-SYSTEMS-INC-386-STEP-386-20-25-33-GATE-ARRA.html

https://thumbs2.imgbox.com/ac/21/uhzoxmQ8_t.jpg (http://imgbox.com/uhzoxmQ8)

GiGaBiTe
June 8th, 2019, 11:16 PM
1. Battery is usually a 3.6/4.5v NiCD/NiMH. You can use regular alkaline AA cells in a holder if you use a blocking diode since motherboards of the time usually charged the CMOS battery. You can confirm this by powering the board and measuring the pins with a multimeter, just don't short them.

2. No idea what the socket is for.

3. Since there's also a 256k jumper next to the socket you pointed out, it's probably to select the amount of system memory installed.

4. Again no idea.

5. If the CPU and the associated 66 MHz crystal are socketed, you can attempt to put a faster CPU in. You'll just need a crystal that's double the speed of the CPU you install, so a 40 MHz 386 would need an 80 MHz crystal.

But unless you have the proprietary memory board that probably goes in the ISA looking slot below the CPU cache chips, that motherboard isn't going to function. The cache chips had me thrown for a loop wondering why it had 160k of cache until I realized it probably uses the 5th 32k chip as a parity module.

RiP2
June 9th, 2019, 06:01 AM
1. Battery is usually a 3.6/4.5v NiCD/NiMH. You can use regular alkaline AA cells in a holder if you use a blocking diode since motherboards of the time usually charged the CMOS battery. You can confirm this by powering the board and measuring the pins with a multimeter, just don't short them.

2. No idea what the socket is for.

3. Since there's also a 256k jumper next to the socket you pointed out, it's probably to select the amount of system memory installed.

4. Again no idea.

5. If the CPU and the associated 66 MHz crystal are socketed, you can attempt to put a faster CPU in. You'll just need a crystal that's double the speed of the CPU you install, so a 40 MHz 386 would need an 80 MHz crystal.

But unless you have the proprietary memory board that probably goes in the ISA looking slot below the CPU cache chips, that motherboard isn't going to function. The cache chips had me thrown for a loop wondering why it had 160k of cache until I realized it probably uses the 5th 32k chip as a parity module.

3. The system memory should be at least 1MB. Maybe it's for the 512/640K base memory but it has an option for it in the BIOS.

5. Won't 80MHz crystal conflict with the ISA bus speed? With 66MHz, ISA works at 33/4=8.25MHz

Yes, the 5th chip is for the parity or maybe write-back cache.

modem7
June 9th, 2019, 04:27 PM
1. What kind of external CMOS battery should I use for it? (Red arrows)
The battery connector looks like the standard one used for a 6V lithium battery. If so, the options at [here (http://minuszerodegrees.net/5170/battery/5170_battery.htm)], for an IBM AT, should be applicable.


2. What's the Instep socket? (Magenta arrow)
From an infoWord magazine, "InSTEP" is a trademark of Everex.
At [here (https://stason.org/TULARC/pc/motherboards/E/EVEREX-SYSTEMS-INC-386-TEMPO-286-12C-EV-2613-E.html)], an "instep board" is shown in the Connections section, with the board appearing to be a form of CPU upgrade.
Do an Internet search using: everex instep 486

Chuck(G)
June 9th, 2019, 08:13 PM
If you don't have the memory board for this thing, as Gigabite mentioned, it's useless. There's no planar base memory without it.

GiGaBiTe
June 10th, 2019, 04:51 AM
3. The system memory should be at least 1MB. Maybe it's for the 512/640K base memory but it has an option for it in the BIOS.

There is no memory installed on that motherboard, you need the proprietary memory daughterboard that fits in the ISA looking slot on the bottom middle of the motherboard, under the CPU cache chips. Unless you have this daughterboard, the motherboard is useless.


5. Won't 80MHz crystal conflict with the ISA bus speed? With 66MHz, ISA works at 33/4=8.25MHz

There was never a defined clock speed for the ISA bus. 808x - 80286 motherboards generally ran the ISA bus at the same speed as the CPU, which lead to a wide range of clocks from 4.77 - 25 MHz. The faster clocks often caused compatibility issues with cards or software that wasn't designed to run so fast. Once you got beyond 8-10 MHz, things got dicey. 386 and onwards had several methods of generating the ISA bus clock. You could run a divider off the CPU clock or have a secondary crystal for the bus. Even later 486 and Pentiums sometimes ran a divider off the PCI bus clock with a 1/3 or 1/4 option.

I suspect that second 14.31818 MHz crystal may be responsible for the ISA bus clock, by using a 1/2 divider, you get a ~7.16 MHz clock.

RiP2
June 12th, 2019, 05:04 AM
The battery connector looks like the standard one used for a 6V lithium battery. If so, the options at [here (http://minuszerodegrees.net/5170/battery/5170_battery.htm)], for an IBM AT, should be applicable.

From an infoWord magazine, "InSTEP" is a trademark of Everex.
At [here (https://stason.org/TULARC/pc/motherboards/E/EVEREX-SYSTEMS-INC-386-TEMPO-286-12C-EV-2613-E.html)], an "instep board" is shown in the Connections section, with the board appearing to be a form of CPU upgrade.
Do an Internet search using: everex instep 486

Are you sure about 6-Volt? I have seen 3.6V too, and not sure if rechargeable or not:

https://thumbs2.imgbox.com/20/c5/hBd00z4G_t.jpg (http://imgbox.com/hBd00z4G)

Thanks for InSTEP info.


There is no memory installed on that motherboard, you need the proprietary memory daughterboard that fits in the ISA looking slot on the bottom middle of the motherboard, under the CPU cache chips. Unless you have this daughterboard, the motherboard is useless.


There was never a defined clock speed for the ISA bus. 808x - 80286 motherboards generally ran the ISA bus at the same speed as the CPU, which lead to a wide range of clocks from 4.77 - 25 MHz. The faster clocks often caused compatibility issues with cards or software that wasn't designed to run so fast. Once you got beyond 8-10 MHz, things got dicey. 386 and onwards had several methods of generating the ISA bus clock. You could run a divider off the CPU clock or have a secondary crystal for the bus. Even later 486 and Pentiums sometimes ran a divider off the PCI bus clock with a 1/3 or 1/4 option.

I suspect that second 14.31818 MHz crystal may be responsible for the ISA bus clock, by using a 1/2 divider, you get a ~7.16 MHz clock.

I have the memory card, I said before that it's all working fine. It has a beautiful OLED-like front panel too :cool:

I was thinking about the 14.31818 MHz crystal too but since I remember, the BIOS could set the ISA bus speed as CPU clock/4 or CPU clock/3
I'll check it again to be sure.

modem7
June 13th, 2019, 02:54 PM
Are you sure about 6-Volt?
Definitely not. That is why I wrote, "If so". Unfortunately, no one has put their hand up and said, "I have that model of motherboard and the battery used is xxxxxx." or "At yyyyyy is what Everex indicates is required for that connector on that model of motherboard." So, everything else that you hear is an opinion. For all we know, for the subject motherboard, Everex require a battery module that contains an isolation diode.

On some motherboards, a 3.6V battery is inadequate/borderline (an example being the IBM AT), or will not last very long. There are some motherboards where the user's manual indicates the use of a 4.5V battery.

If you have the ability, draw a circuit diagram of the associated circuitry, and someone here can then provide a very informed opinion.


I have seen 3.6V too, and not sure if rechargeable or not:
The 3.6V battery that you pictured is lithium (not lithium-ion), and accordingly, is not rechargeable. That example was made in Feb 1996; 23 years ago. New, it would have measured about 3.7V. Today, it will be substantially less.

modem7
June 15th, 2019, 03:55 PM
Because the subject of 'CMOS setup' batteries appears periodically, I created an information web page at [here (http://minuszerodegrees.net/battery/cmos/vintage_motherboard_batteries.htm)].

Chuck(G)
June 15th, 2019, 04:45 PM
I have the memory card, I said before that it's all working fine. It has a beautiful OLED-like front panel too :cool:

I was thinking about the 14.31818 MHz crystal too but since I remember, the BIOS could set the ISA bus speed as CPU clock/4 or CPU clock/3
I'll check it again to be sure.


The 14.3818 crystal is there to provide a spec-required signal on the ISA bus--and also quite likely to clock the 8254 counter-timer. You don't want to fool with that.

RiP2
June 28th, 2019, 02:46 AM
The 14.3818 crystal is there to provide a spec-required signal on the ISA bus--and also quite likely to clock the 8254 counter-timer. You don't want to fool with that.

Well, I replaced the 66MHz crystal with 80MHz and it worked fine. Now the CPU works at 40MHz, 20% faster.

But I'm still worry about the ISA bus speed if now it's working at 10MHz or not:

https://thumbs2.imgbox.com/9f/6d/MrP6F9UK_t.jpg (http://imgbox.com/MrP6F9UK)

I have also measured the voltage of external battery connector and it's 4.8V but not sure what kind of battery I should use for it, 3.6/4.5/6-volt :confused: