Is the 66mhz crystal known to be good?

cyclone3d wrote on 2020-08-16, 19:05:

Is the 66mhz crystal known to be good?

Indeed it does work, and it came from another dx66 board, an ISA Symphony chipset board.

You changed the CPU, but you might still be running other parts out of spec. You'd better try to get your motherboard manual to see what the jumpers do.

Anonymous Coward wrote on 2020-08-17, 00:18:

You changed the CPU, but you might still be running other parts out of spec. You'd better try to get your motherboard manual to see what the jumpers do.

That's what I figured, which is why Iwas looking at that time delay chip. There aren't a huge amount of jumpers, but I am still playing with it. There is no manual, only the th99 page.

It's an odd problem. I had other discrete logic boards, both 386 and 486, and they never gave me problems going from 25 to 33 or 40 Mhz

Hmm.. changing crystals on many old boards usually meant changing some jumpers to divide the ISA clock to make sure it still at 8mhz and sometimes also changing memory timing. Many old boards used the crystal to establish a base but others also used it to time many other things. Simple math: 50Mhz/2 for 25Mhz cpu then /3 ~ 8.33Mhz ISA. With 66Mhz/2 for 33Mhz cpu then /3 ~11Mhz ISA. Just an example...

Horun wrote on 2020-08-17, 01:55:

Hmm.. changing crystals on many old boards usually meant changing some jumpers to divide the ISA clock to make sure it still at 8mhz and sometimes also changing memory timing. Many old boards used the crystal to establish a base but others also used it to time many other things. Simple math: 50Mhz/2 for 25Mhz cpu then /3 ~ 8.33Mhz ISA. With 66Mhz/2 for 33Mhz cpu then /3 ~11Mhz ISA. Just an example...

Yep, 50 and 66 mhz crystals here. 80 on the other boards. Ram is 60ns. ISA bus is supposed to be fixed at8mhz and is probably 8.33, but I have not pulled out ny counter to check it.

Moogle! wrote on 2020-08-17, 02:01:

Yep, 50 and 66 mhz crystals here. 80 on the other boards. Ram is 60ns. ISA bus is supposed to be fixed at8mhz and is probably 8.33, but I have not pulled out ny counter to check it.

Please post a picture of your board. Being the board name is: Micronics DX25 I am guessing it was not designed to run 33Mhz. In comparison to the Biostar PB, PV, UCV or UIV models which did not rely on just a crystal to set bus speeds and supported 25 or 33 Mhz or more..just using those as an example.

What year was the board manufactured? Is it 1980s vintage?

Horun wrote on 2020-08-17, 02:26:

Moogle! wrote on 2020-08-17, 02:01:

Yep, 50 and 66 mhz crystals here. 80 on the other boards. Ram is 60ns. ISA bus is supposed to be fixed at8mhz and is probably 8.33, but I have not pulled out ny counter to check it.

Please post a picture of your board. Being the board name is: Micronics DX25 I am guessing it was not designed to run 33Mhz. In comparison to the Biostar PB, PV, UCV or UIV models which did not rely on just a crystal to set bus speeds and supported 25 or 33 Mhz or more..just using those as an example.

https://imgur.com/a/H7kUJYI Don't have time for a better picture for the moment.
https://th99.classic-computing.de/m/M-O/31857.htm

Anonymous Coward wrote on 2020-08-17, 03:11:

What year was the board manufactured? Is it 1980s vintage?

Board was built in May of 1990.

Hmm ok found this at the Archied Micronics website: http://web.archive.org/web/19970607130047/htt … 86.htm#prod_025
and the manual #00025 was archived from their ftp site here: https://www.infania.net/misc/moboarchive/Micr … nuals/00025.txt

No mention of any other processor but a 486-25. It is possible one or more of the switches labeled "Factory configured - do not alter" could have to do with the chipset and ISA bus divider as labeled at the TH99 page which could then lead to getting a 33Mhz to work. Will keep looking as there may be some other FAQ's or something somewhere....

Horun wrote on 2020-08-17, 22:31:

Hmm ok found this at the Archied Micronics website: http://web.archive.org/web/19970607130047/htt … 86.htm#prod_025
and the manual #00025 was archived from their ftp site here: https://www.infania.net/misc/moboarchive/Micr … nuals/00025.txt

No mention of any other processor but a 486-25. It is possible one or more of the switches labeled "Factory configured - do not alter" could have to do with the chipset and ISA bus divider as labeled at the TH99 page which could then lead to getting a 33Mhz to work. Will keep looking as there may be some other FAQ's or something somewhere....

Nice find with the internet archive. I don't know why I didn't try that, as I was there recently looking to see if there were any bios updates for my JX30WB.

It does have a few unlabled jumpers and switches, but some of the jumpers are just pads. I will need to get some headers to solder down. I am also going to pull up that DS1000-50, put a socket down, and install something faster if I can find a suitable chip.

The DS1000-50 is typically used to add wait states for ram/cache/VLB/etc, that much I know so maybe replacing it could help. The lower the -# the lower the nS delay from original signal (ie: -50 =2nS per tap or 10nS to tap5, -75=3nS per tap or 15nS to tap5) if I read the data sheet correctly.

I'm also wondering if there is a check built into the BIOS that checks the CPU speed. I doubt it, as I think only IBM did that.

Well, if that were the case you could always try swapping in MR-BIOS. They have an ASIC 386 version.

Well, I can at least eliminate that theory. Doesn't boot at 33Mhz with the Mr. Bios either. It also eliminates a secondary theory about the eproms being too slow.

Moogle! wrote on 2020-08-17, 23:15:

Nice find with the internet archive. I don't know why I didn't try that, as I was there recently looking to see if there were any bios updates for my JX30WB.

Did you find the BIOS for the JX30WB ? The Archive link lists: "JX30WB P/N 09-00192
"These flash BIOS updates are for Micronics distribution boards only. They should NOT be used on our boards used in Gateway, Micron, or EDS systems.
Name: JX30WB (ver -02), File: JX30WB-2.EXE, Size: 68801 bytes
Fixed problems with Trident 9420 video card operating at 64MB boundary"

I got it, the .BIN is dated 1/16/1995 and has the internal string: E780486 ROM BIOS PLUS Version 0.10 JX30WB-02

I believe that was the version already on my board.

Minor update. Got the DS1000 up off the board, but I somehow managed to break three of its legs off. Got a socket down and tried a compatible chip from another board (one of those bigger, blockier types) with 40NS delay. It tries to boot with that, but it's gets stuck with 0A on the POST card. I then went and found another one (again, another big blocky one) that was also 50NS like the original Dallas chip, and it does boot with that. Neither works at 33Mhz though.

Moogle! wrote on 2020-08-19, 18:25:

Minor update. Got the DS1000 up off the board, but I somehow managed to break three of its legs off. Got a socket down and tried a compatible chip from another board (one of those bigger, blockier types) with 40NS delay. It tries to boot with that, but it's gets stuck with 0A on the POST card. I then went and found another one (again, another big blocky one) that was also 50NS like the original Dallas chip, and it does boot with that. Neither works at 33Mhz though.

I think you need to slow/add-wait time, not speed up/reduce. The DS1000-40 is roughly 20% less wait time by TAP5 than DS1000-50. By increasing from 25Mhz to 33 you are increasing speed by 30%. If you could find a DS1000-60 or -75 it would nearly balance that speed increase by adding more wait time. One thing: all of the Dallas DS1000 -20 thru -100 still have 2nS as nominal delay on Taps 1 and 2. So if some critical part was clocked/signaled off Tap1 or Tap2 any of those could be getting signals too quickly no matter which DS1000 you used at 33Mhz. Think of it like a typical VLB controller and you increase board clock to 40Mhz from 33Mhz, you need to add wait states either on board to VLB if it has them or on the VLB card itself (thru jumpers). Yes am simplifying things but going to a DS-40 is going wrong direction.