The Dallas clock chip in my Pentium PC finally gave out.

[Haruspex]

I have a Pentium 233 MMX PC I built a while ago. The ASUS motherboard I had it all running on was on borrowed time, largely due to the 30 year old Dallas clock chip. For those that don't know, it's a common component in many old PCs that works to keep the time and BIOS settings. It has it's own battery built-in, and there's no replaceable CMOS battery.

I went to play some Space Quest III the other day, and finally saw the dreaded message that the clock chip had failed. I can boot into it anyway, but the time has come to do something.

As a replacement, I have ordered an Asus TX97-XV Socket 7 motherboard with an actual, replaceable CMOS battery.

A couple of things to note:

My previous motherboard is currently populated with 64 GB worth of SIMM memory modules. This new board has the needed SIMM slots, but it also has two DIMM slots. The manual states I cannot use both. Either use the SIMMs, or the DIMMs. What kind of performance improvement might I see if I plug a couple of 32 MB DIMMs in there instead?
Edit: Found an answer here.[www.vogonswiki.com]

The speed gain from using SDRAM compared to EDO is in the range of a few percent.

I'll just stick with the EDO RAM then.

I'm currently using a PCI S3-Virge VGA card just for 2d along with a Voodoo 4 MB 3d accelerator. This motherboard has an onboard ATI Rage-II VGA chip built in with the memory fully expanded for I think 2 MB of onboard video memory. Benchmarks seem about even for 2d stuff, and I don't plan on using the cards for anything 3d accelerated. Should I use that on-board ATI chip or stick with my S3-Virge?

I also have an ISA Soundblaster AWE 64 in there. No questions about it. I just wanted to mention it.

[_I_]

more likely to be a bad cap
look over the board for a leaky or bulged cap

[Haruspex]

引用自 _I_：

more likely to be a bad cap
look over the board for a leaky or bulged cap

Caps are good. It's 100% that Dallas chip that died on me. Common problem with these. Sometimes you can find new-old stock of one and desolder/replace. I've seen someone else dremel into one and solder a button battery on top of it, but I'm not going to do that.

[SimicEngineer]

It sounds like you've done your homework, but I'm surprised that there's not a compatible replacement (e.g. the DS12887+, which is still an active product from Analog Devices and stocked by distributors), or at the very least some clever adapter that can be ordered via eBay or Tindie or wherever. This seems like the sort of chip that would be lurking in all kinds of industrial equipment that will still be running 20 years from now.

[Haruspex]

引用自 SimicEngineer：

It sounds like you've done your homework, but I'm surprised that there's not a compatible replacement (e.g. the DS12887+, which is still an active product from Analog Devices and stocked by distributors), or at the very least some clever adapter that can be ordered via eBay or Tindie or wherever. This seems like the sort of chip that would be lurking in all kinds of industrial equipment that will still be running 20 years from now.

Probably. There are ways, among them the two I mentioned. I've intended to replace the motherboard with something that has a normal, replaceable CMOS battery since I first got it, but it was working fine so I didn't. This new board is a couple of years newer than the old one. (And in the mid 90s a couple of years might as well have been decades.)

[xSOSxHawkens]

So as someone with a very similar system (P233/mmx, S3, Dual Mem MB) this is my two cents:

Use DIMMS : Re is that you can max the ram much easier. basic PC100/133 ram will more than likely fully exceed anything the board could do with a DIMM of the time (which would have been PC 33 or 66). I run a single 512MB stick of PC133 in my MMX rig and the stick gets chipset limited to 256MB addressable. But the MB has had all the memory related anything brought to its fastest and tightest and as far as the board is concerned it might as well be golden sample memory. In reality its just a few years older than the rest of the rig but still def within spec of an End or Life upgrade from when the machine was still usable for a daily driver.

Keep the S3 - On a system of that age, even if you have one that has 256MB or 512MB usable ram, the memory will still be at a premium, more so if you are asking any remotely modern ability of the machine (mine tri-boots and one option is XP SP3). Giving up a couple megs to the integrated when the S3 was by all rights a fantastic 2D card (if an abysmal worlds first 3d) is just not smart. Keep the S3 and run your RAM full to the system.

Last bit if see if your older board is still serviceable without reboots. Without looking into the model I am not sure, but I know most of the boards from that era had no issues without a CMOS. In fact one of my older boards had a broken CMOS battery latch and never had one in it. Just keep the system powered up and the BIOS settings should be fine. Only downside is having to reset things on a power cycle. I could do a full sweep of settings in about 60 seconds with that system though.

[Haruspex]

引用自 xSOSxHawkens：

So as someone with a very similar system (P233/mmx, S3, Dual Mem MB) this is my two cents:

Hey, thanks for that. I think I might have a couple of 256 GB sticks of PC133 laying around somewhere. I was under the impression that going beyond the cache limitation of 64 MB would result in reduced performance. Maybe it does, but not enough of one to matter, and perhaps that would be offset by the performance gain of using SDRAM. Maybe I'm overthinking it too.

Another issue I've run into is the power supply. Well, not really an issue, but more of an oversight. The new motherboard apparently takes an ATX power supply with a 20 pin connector, while the old one was running off an AT power supply. The pros are I can use a modern power supply that's less likely to burn my house down, and it will be quieter than the vaccuum cleaner sound the AT power supply fan makes. The negatives are that vacuum cleaner sound was kind of nostalgic, and I'll no longer get the orange "It's now safe to turn off your computer" message when I shut it down. Modern power supplies seem to skimp on the 5v rail these days, but the EVGA 400 watt one I'm planning on putting in there offers 15 amps, so that should be fine.

[Crashed]

People have figured out how to hack these modules to attach a fresh battery - https://www.youtube.com/watch?v=oyNp-u5nl-8

[xSOSxHawkens]

引用自 Haruspex：

Another issue I've run into is the power supply. Well, not really an issue, but more of an oversight. The new motherboard apparently takes an ATX power supply with a 20 pin connector, while the old one was running off an AT power supply. The pros are I can use a modern power supply that's less likely to burn my house down, and it will be quieter than the vaccuum cleaner sound the AT power supply fan makes. The negatives are that vacuum cleaner sound was kind of nostalgic, and I'll no longer get the orange "It's now safe to turn off your computer" message when I shut it down. Modern power supplies seem to skimp on the 5v rail these days, but the EVGA 400 watt one I'm planning on putting in there offers 15 amps, so that should be fine.

The biggest issue with ATX will be the modern voltage/amperage rail configs that you allude to with the 5v. And all the others tbh. Might do well enough pulling an older OEM supply from a pre-build as long as its caps are still solid. Anything with 250w or more will be plenty for an AT styled system.

If you are getting a new MB anyway, think about a Super Socket 7 with an AGP slot. Some are out there. They are rare, but you can get something that will not only run the Pentium but also a good selection of faster AMD chips. AMD kept Socket 7 alive to much higher clock speeds than Intel ever went, and the performance on later AMD chips on the socket is much faster in many ways.

[_I_]

if the board has a battery soldered in, you can remove it and add your own lithium cr2032 3v holder and cell

[SimicEngineer]

引用自 _I_：

if the board has a battery soldered in, you can remove it and add your own lithium cr2032 3v holder and cell

The issue is that with these chips the battery isn't merely soldered down, it's sealed inside the RTC/CMOS chip package instead of being connected to the board. You can't add a battery holder without cutting it open.

[Haruspex]

引用自 xSOSxHawkens：

If you are getting a new MB anyway, think about a Super Socket 7 with an AGP slot. Some are out there. They are rare, but you can get something that will not only run the Pentium but also a good selection of faster AMD chips. AMD kept Socket 7 alive to much higher clock speeds than Intel ever went, and the performance on later AMD chips on the socket is much faster in many ways.

I would, but this build keeps creeping up there in spec. When I first started putting this together, the original intent was to actually build a 486 running DOS and Windows 3.1. As I found parts though, it just started creeping up there eventually into a Pentium class system with 3d acceleration running Windows 98SE.
This is my time capsule. It's a corner of my office where I can pretend it's the mid 90s again. A simpler time. The closer to modern it gets the more it defeats the purpose. Right now it's kind of at a sweet spot. It's almost like that PC my rich friend had and he would blow us all away by showing us 3d accelerated Tomb Raider, Quake and Carmageddon in the blisteringly high resolution of 640x480 before I went home to my 486sx with 4MB of RAM that I couldn't even get to run Doom.

[Haruspex]

引用自 Crashed：

People have figured out how to hack these modules to attach a fresh battery - https://www.youtube.com/watch?v=oyNp-u5nl-8

As I mentioned, and I considered it, but nah.

[_I_]

ok, thats a weird design, but soldering in a new ic socket to replace it is not difficult

a socket and modded pcb is $30 shipped
https://www.ebay.com/itm/134217827379

if the battery pins went straight to the board, it would be easy to just add a new battery on the old one

[Haruspex]

引用自 _I_：

ok, thats a weird design, but soldering in a new ic socket to replace it is not difficult

a socket and modded pcb is $30 shipped
https://www.ebay.com/itm/134217827379

That's a really neat product I didn't know existed! I've already ordered the new motherboard, but I'll file this away for future reference. Thanks!