DOSBox's maximum memory is 64MB and it runs lots of games...

64MB were good to have with Windows NT and later back then.

OK, it sounds like 64mb might be the sweet spot then. Although I did find a couple of RAM chips which might be 32mb but I can't really tell until I try them.

Check your mobo's max cacheable memory limit. You really don't want to exceed it.

It says that you can set the secondary cache size to 128kb, 256kb or 512kb. If set to 512km the cacheable range is write-through 128mb and write-back 64mb. Does that mean I shouldn't exceed 64mb or 128mb?

rick12373 wrote:

I have ordered one of those chips from eBay. If I use it and get it to work I will let you know.

Excellent! Good luck, I would be very interested to hear if this works, or not.

rick12373 wrote:

In that step by step guide to hacking the chip he says right at the end that if he were to do it again he would try drilling some holes in and soldering in some wires so that an external battery can be connected. He has marked on a picture where this should be done but without paying and registering the site will not let you see a big version of the picture. That is annoying as it sounds like it may be an easier way to fix it.

That information can be seen here -

http://purpleavenger.blogspot.com/2006/09/hac … 7-rtc-chip.html

rick12373 wrote:

It says that you can set the secondary cache size to 128kb, 256kb or 512kb. If set to 512km the cacheable range is write-through 128mb and write-back 64mb. Does that mean I shouldn't exceed 64mb or 128mb?

You can't just set the cache size to whatever you desire. You have to choose the cache based on the installed cache SRAM chips.

rick12373 wrote:

It says that you can set the secondary cache size to 128kb, 256kb or 512kb. If set to 512km the cacheable range is write-through 128mb and write-back 64mb. Does that mean I shouldn't exceed 64mb or 128mb?

The L2 cache jumpers should correlate with the amount of cache actually sitting on the board.

Installing more memory than the board is able to cache slows down performance, but only if your software actually uses the uncached memory range.
In case you're running DOS, this is rarely the case, since there is no real memory management, and DOS applications fill the memory from "bottom up". There are not many DOS games requiring more than 16MB, and those with higher memory requirements usually run too slow on a 486 anyway.

I switched on the power and hooray, there is still charge in the Dallas chip! So I will leave it as it is until it stops working. At which point I will try the hack first and if I mess that up I will get somebody with better solder skills to put the new chip in that I will have.

I haven't put in a hard drive yet. Will the BIOS be able to detect or will I have to change some settings in there to get it working. Right now I only have some spare 40gb drives. Do I need to limit their capacity by using the jumpers? Is there anything else I will need to do with the hard drive to get it working?

Regarding the Dallas RTC, is your current RTC soldered directly on to the motherboard, or is it socketed to the motherboard? If it looks like you can pull the Dallas RTC upwards, away from its little socket on the mobo, then you can test your new RTC to see if it works OK, then replace your current one. (If it's socketed, it looks like it is sitting on top of a thin black strip of plastic.) And no soldering will be required either.

About the harddisks: it won't kill the computer so you can try your options...

I'll have a closer look at the RTC later. With the hard disk though I have vague memories that maybe these old MB's do not detect HD's and that you had to choose the right settings. I'll have a try today anyway.

Would it be easier to install Win 95 and use the DOS that comes with that? What version of DOS is it? On my Pentium 2 machine I have Win 98, although I have it boot right in to DOS.

Anyway, thanks for the advice so far. Phew, that wasn't easy typing all this on a DSi!

IMHO, I would just go for "pure" DOS. Leave Windows 95 for a faster pentium based system. I think a lot of PCI based 486 mobos automatically detect the HDD settings, from within the BIOS set up area. If there is no HDD auto detection facility there, then you enter in the values manually - you can usually get these values from a sticker on the face of the HDD.

Which version of DOS should I use? Seem to remember 6.22 or something was good. I don't have DOS on floppy anymore. Guess I will search for a copy.

I use MS-DOS 6.22 from 3 Microsoft 3.5" 1.44MB floppy disks. I bought it cheaply from ebay. I did a quick search on ebay (co uk), and there's lots left. Same too for ebay.com. (BTW, I think there are other DOS versions you can use, eg Free DOS, but currently I only know a bit about MS-DOS 6.22.)

I recommend using (IBM) PC-DOS 2000, consumes less memory so you have more conventional memory left for games

Is there any way you can burn that to CD, boot from the CD and then install it from there? Floppies and so unreliable. Can you even boot to CD on old 486 boards?

rick12373 wrote:

Is there any way you can burn that to CD, boot from the CD and then install it from there? Floppies and so unreliable. Can you even boot to CD on old 486 boards?

pc-dos 2000 comes on a cd version too but 486 bios'es have no support to boot from cd's

I see, oh well. I suppose I have to go the way of the floppy disk 🙁

Well, I don't have PC-DOS 2000 and don't seem to be able to find it anywhere online. Would DOS 6.22 be the next best thing?