Re: Is it possible to change the DAC on a CT1740 ?
Posted on 21 minutes ago
Yes. Thanks. That's what I was asking more or less.
Is it possible to change the DAC on a CT1740 ?
Posted on Today, 05:58
Possible to swap out the 1701 DAC for the newer 1703? Anyone know anything about this? Has it been done? Or tried, crashed and burned?
Re: 486 cache configuration questions.
Posted on 2021-06-28, 22:32
Ok thanks on the clarification and explanation. It fits with what I observed and what I might expect. Sooner or later I'll have amassed enough information to make the "missing manual". Most of the DIPs which are documented are for memory setup.. The remaining 8 or 9 switches are marked as "reserved" …
Re: 486 cache configuration questions.
Posted on 2021-06-21, 07:52
Super! That helps clarify and confirm what I was beginning to think. So. The third chip in the TAG RAM is for dirty-bits, needed on older chipsets for write-back support for the L2. Alright. Can I assume this MIC 461/462 chipset then supports write-back even though the L1 cache onboard the processor …
Re: 486 cache configuration questions.
Posted on 2021-06-19, 23:31
I decided to revisit this, having just repaired, or, rather, properly reconfigured a board from this family. The above sort of makes sense - but I'm not clear on how the sizes interrelate. Like stated above, it's direct-mapped. And I would assume write-through considering the early era and 386 …
Re: Can't get into CMOS setup on old 486.
Posted on 2021-06-15, 19:59
One other brief note. Your site lists the optional numeric processor as a 3167. This is a 486, so it would use the Weitek 4167.. Many years ago I saved this from this: http://support.mpccorp.com/tech_support/MOTHERBD/MICRONIC/gem4_33/00000005.html Last Modified: 11/15/2003, Author: TCM, Revision: 1. …
Re: Can't get into CMOS setup on old 486.
Posted on 2021-06-13, 23:08
mR_Slug wrote on 2021-06-13, 19:33: Can we use your picture to document the board here: http://www.win3x.org/uh19/motherboard/show/3716 Yes of course. Additionally here is the Micronics M810 memory card, which provides an additional 32MB via Bank2 and Bank3. 64MB system total. You may also use this …
Re: Can't get into CMOS setup on old 486.
Posted on 2021-06-13, 22:24
According to the Phoenix BIOS Reference Book the external cache controller is almost last to tested or initialized. It doesn't say anything about the testing the cache memory. I'm inclined to believe it just checks for the presence or absence of the controller and maybe a "ready" signal of some sort …
Re: Can't get into CMOS setup on old 486.
Posted on 2021-06-13, 08:50
I can't edit the title. But I could add a line to the first post. I will look up the mainboard numbers tomorrow. There might be two numbers, one for the DX and another for the DX2 version. But they would behave the same. These motherboards were typically sold only as OEM parts to computer assemblers …
Re: Can't get into CMOS setup on old 486.
Posted on 2021-06-13, 08:24
The configuration of the Level-2 cache. The board's jumpers and switches were set for cache size of 256K, but the installed cache was actually 64K. They looked to be the original factory-installed chips, just that somehow the board was mis-configured. 8 chips of 8K x 8 SRAM vs 8 chips of 32K x 8 …
Re: Can't get into CMOS setup on old 486.
Posted on 2021-06-12, 21:21
For Real! Thanks to all! The world now has one more slightly smarter hobbyist, and another functional vintage motherboard. Filename 1.png File size 854.36 KiB Views 94 views Filename 2.png File size 761.34 KiB Views 94 views Filename 3.png File size 1.23 MiB Views 94 views
Re: Can't get into CMOS setup on old 486.
Posted on 2021-06-12, 05:51
Ok. I think the L2 cache might be a problem. Working on it.
Re: Can't get into CMOS setup on old 486.
Posted on 2021-06-11, 18:27
No go with the 8242 keyboard controller out of circuit. No video even. I feel confident the chip is working. I don't believe there's any damaged traces in that area of the board. Unless it's highly intermittent.. Or under a soldered component. Having a battery connected (or not) doesn't seem to make …
Re: Can't get into CMOS setup on old 486.
Posted on 2021-06-11, 09:22
Not much is left. I have yet to swap the CPU. But I think it's alright. I have high confidence the following stuff is in good working order: CPU SIMMs Power Supply Videocard BIOS EPROMs 82C206 IPC w/CMOS memory, RTC, IRQ & DMA controllers 8242 Keyboard controller w/Phoenix firmware Remaining items …
Re: Can't get into CMOS setup on old 486.
Posted on 2021-06-11, 08:00
Alright. I'm keeping the bastardboard off to the side of my workbench, but hooked up a power supply, monitor, keyboard, videocard and miscellaneous front panel stuff like Turbo, Reset, KeyLock, TurboLED, PowerLED, and Speaker. I have a 3.5" drive and a Multi I/O board standing by, but not connected. …
Re: Can't get into CMOS setup on old 486.
Posted on 2021-06-11, 05:31
A brief tip when using a 'prommer and old old old chips: I had to clean the sides of the IC's pins before I got a consistent read. This is because regular motherboard sockets wipe two sides of the pins. Fine. That's normal. But the TL866 and all other ZIF-sockets like it make contact on the sides …
Re: Can't get into CMOS setup on old 486.
Posted on 2021-06-11, 05:07
Sorry about that if I mis-worded anything. Yes. My ripped BIOS from the original board worked fine in PCEM. I found the next revision BIOS, G22-2 in a pile of files. Plugged it into PCEM. And it worked fine there too. I was able to get into the screens and make changes, in PCEM. I used 2 different …
Re: Can't get into CMOS setup on old 486.
Posted on 2021-06-10, 22:52
Thanks for the options and suggestions. Unfortunately the board remains stubborn and recalcitrant. Maybe there's some secret agent stuff in there or some hidden coded message! The board is cosmetically perfect and would pass for NOS. It's nostalgic, coming from a time when I got into PCs. But …
Re: Can't get into CMOS setup on old 486.
Posted on 2021-06-10, 11:10
This board and BIOS should do shadowing. This is also a board that has many design cues taken from the 386 era. It's not refined with a later chipset, or VLB, or PCI, or support for multiple CPU types & voltages. It supports the out of style Weitek 4167. The BIOS options are not extensive. Basically …
Re: Can't get into CMOS setup on old 486.
Posted on 2021-06-10, 08:43
In a couple of weeks I can get to my POST card. I hooked up a speaker and there were no beeps of any kind. Total silence. Including when I made it make the mis-configured (via incorrect DIP switch setting) RAM parity error. I merged the HI + LO dumps with romwak and looked through the resulting …
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