Breathing new life into 1981 IBM 5150

[Eudimorphodon]

The "98" portion is interesting, and matches with the "98" described in the 'Multiple bit failure' section of [here].

That is interesting (thank you for the link, BTW). The first link I saw on what this code meant made it sound like the whole four digits were a left-offset (first 16 bits out of 20) HEX address, I didn't realize it was split 4K page + bit indicator. So it's actually blowing up directly at the 576K mark.

Since it gets into BASIC, how about something like this?
5 defint a-z
10 def seg=&H9000
20 for X=0 to 255
25 print "addr: ";X
30 for Y=0 to 255
40 poke X,Y
50 Z=peek(X)
60 if Z<>Y then goto 1000
70 next Y : next X : end
1000 print "ERROR AT: "; X ;" WROTE: "; Y ;" READ: "; Z

This would tell you if the RAM is actually there or not.

 

[VERAULT]

That is interesting (thank you for the link, BTW). The first link I saw on what this code meant made it sound like the whole four digits were a left-offset (first 16 bits out of 20) HEX address, I didn't realize it was split 4K page + bit indicator. So it's actually blowing up directly at the 576K mark.

Since it gets into BASIC, how about something like this?
5 defint a-z
10 def seg=&H9000
20 for X=0 to 255
25 print "addr: ";X
30 for Y=0 to 255
40 poke X,Y
50 Z=peek(X)
60 if Z<>Y then goto 1000
70 next Y : next X : end
1000 print "ERROR AT: "; X ;" WROTE: "; Y ;" READ: "; Z

This would tell you if the RAM is actually there or not.

Ok So Im going to chock this up to possibly being tired and "dumbing up the process".. Possibly... Maybe....

Here is the board and you can see the vga card far left.. Middle Lo-tech RAM card and right XT-IDE


You were right about the less than 64KB showing up in BASIC. I misread it:


I decided to try the tests at 608KB and 640KB using the board settings from http://minuszerodegrees.net/5150/ram/5150_ram_16_64_SW2.jpg

I typed in the BASIC program and ran it

It ran to 255 and ran the same with both the 608KB and 640KB settings on the mainboard SW2 (tests ran without the XT-IDE in place!!)


I decided to put the XT_IDE card in and it booted with no ERROR!? I dont get it
I ran MEM

Then I ran Checkit 3


I really dont understand what happened or why its working now.
I have the SW2 mainboard configured as ON, OFF, ON, ON, OFF, OFF, OFF, OFF FOR 640kb AND IT SEEMS T0 BE WORKING FINE. This is with the XTIDE and VGA and LOTECH in place.

 

[Eudimorphodon]

Maybe the lo-tech card has an iffy DIP switch.

 

[VERAULT]

They are not the best feeling SMD dips to be honest.. Which is a shame because the wiki shows standard throughhole dipswitches: https://www.lo-tech.co.uk/wiki/Lo-tech_1MB_RAM_Board

Currently running the 8088mph Demo on VGA.. So its all jacked up.. but running. Systems seems fine I suppose. Unless there are other tests I should run.
This system WILL have the XTIDE inside of it but like I mentioned I WILL install a CGA or Hercules card (or IBM mono card) as I know I have a bunch.

 

[Eudimorphodon]

Cheap DIP switches make me sad. And even good ones can be messed up if soldered incorrectly. Hopefully it'll behave, but be wary of it possibly hanging loose again if you adjust the switches after you get rid of the VGA card.

 

[VERAULT]

Ill keep that idea on the backburner when I make the switch.

To be honest I was quite surprised I left the XTIDE on its stock settings and didnt make any adjustments to the Lo-TEch card for the XTIDE bios area and it works..

 

[Eudimorphodon]

To be honest I was quite surprised I left the XTIDE on its stock settings and didnt make any adjustments to the Lo-TEch card for the XTIDE bios area and it works..

The BIOS banner said it was set to C800, which is a safe setting for most VGA cards.

FWIW, digging around it looks like it's an undocumented feature that you can set the switches in a 5150 with that BIOS to directly recognize more than 640K. MinusZeroDegrees' chart doesn't cover this option, but extrapolating from what's there I *suspect* the switch setting for SW2 on the motherboard for 704K is "11010". But don't quote me on that. Something to fool with after you put the CGA or Hercules card in there. (Remember, B and C are going to need to stay off on the Lo-Tech for video and the XTIDE BIOS.) If you wanted to be really bold you could try hacking the XTIDE card to put the BIOS at F000, but like I said earlier I'm not 100% sure that's usable in the 5150.

 

[VERAULT]

I realize EARLY bios have an issue with this. But I have seen it in in several 5150's that they can reach 640KB so I had no doubts about that.

As far as MORE THAN 640KB... I am all ears. I would love to hear how.

 

[rmay635703]

If you have the correct graphics card you can get more than 640

You will need an app to clear and open up the memory beyond 640k, these existed even in antiquity

 

[Eudimorphodon]

As far as MORE THAN 640KB... I am all ears. I would love to hear how.

Well, that's what I just laid out. I don't think the issues you had here had anything to do with your BIOS, I'm 99.44% sure the switch on your Lo-Tech card for the 9000 page of RAM was being stupid and just magically cured itself at some point when you were shuffling cards.

Anyway, to reiterate a little more clearly... if you look at the chart of SW2 switch settings you'll notice that the settings for 576K and up are the same as the settings for 64K and up except SW5 is flipped from "1" to "0". As evidenced from this thread apparently the 5150 is happy to keep counting higher; in that thread the user set their card for 96K of additional memory over the 640K mark (IE, they set the switches the same as the 224KB setting except they reversed SW5) and the BIOS will indeed do it. And then the rest of that thread is an argument about whether what they did is "safe" or not because technically the hardware they did this with creates a hardware conflict between the RAM card they added (a clone of the lo-tech) and CGA's built-in video memory. (Optimistically it probably won't physically burn anything up, but it technically wrong and *may* possibly break some CGA software that leverages a hardware oddity that makes the same CGA RAM accessible from two different address ranges.)

Anyway, I recommend you don't do what that poster did with the hardware, IE, enable the "B" page on the Lo-tech for two reasons, A: it is a conflict with CGA, whether it burns up your machine or not, and B: it won't work with Hercules at all... but there is no problem at all with enabling the A page. Again, going by the pattern that seems to be in play here to try this:

A: Set SW2:3 on the Lo-Tech to "on"
B: Set the first five positions of motherboard switch SW2 to "on - on - off - on - off"

Supposedly if this works you'll get 704K recognized without any additional drivers. See what happens, I guess.

 

[VERAULT]

Anyway, I recommend you don't do what that poster did with the hardware, IE, enable the "B" page on the Lo-tech for two reasons, A: it is a conflict with CGA, whether it burns up your machine or not, and B: it won't work with Hercules at all... but there is no problem at all with enabling the A page. Again, going by the pattern that seems to be in play here to try this:

A: Set SW2:3 on the Lo-Tech to "on"
B: Set the first five positions of motherboard switch SW2 to "on - on - off - on - off"

Supposedly if this works you'll get 704K recognized without any additional drivers. See what happens, I guess.

Sure I can give this a try.

 

[VERAULT]

SNAZZY!




If this is conflict free Memory I would say this Lo-tech card was a really really good purchase.

 

[Eudimorphodon]

... To be crystal clear, this is only really safe after you switch to a Hercules or CGA card. If you run any software that triggers an EGA or VGA graphics mode very bad things are going to happen. (In text mode VGA just uses the CGA memory area. This memory area you just enabled sits right on top of where the EGA/VGA-specific graphics modes live.)

 

[VERAULT]

... To be crystal clear, this is only really safe after you switch to a Hercules or CGA card. If you run any software that triggers an EGA or VGA graphics mode very bad things are going to happen. (In text mode VGA just uses the CGA memory area.)

Understood! This is honestly what I was looking for in the long run for a permanent setup for this machine.

 

[VERAULT]

I suppose now I have the RAM issues covered. Time to get back to the 180KB single sided floppy Drive with this computer.

 

[maxtherabbit]

Well, that's what I just laid out. I don't think the issues you had here had anything to do with your BIOS, I'm 99.44% sure the switch on your Lo-Tech card for the 9000 page of RAM was being stupid and just magically cured itself at some point when you were shuffling cards.

This


Congrats on joining the 700k club

 

[VERAULT]

This


Congrats on joining the 700k club

Honestly this is the first time I have ever done this magic trick. I watched a video by Trixter but I guess I assumed it only worked on 8086 and 286 class machines. All those years using my 5160 I had no idea MORE ram was possible.

 

[maxtherabbit]

Honestly this is the first time I have ever done this magic trick. I watched a video by Trixter but I guess I assumed it only worked on 8086 and 286 class machines. All those years using my 5160 I had no idea MORE ram was possible.

That video was forged in the fires of my PC-DOS 3.2 on 5150 thread

 

[VERAULT]

Well, that's what I just laid out. I don't think the issues you had here had anything to do with your BIOS, I'm 99.44% sure the switch on your Lo-Tech card for the 9000 page of RAM was being stupid and just magically cured itself at some point when you were shuffling cards.

Anyway, to reiterate a little more clearly... if you look at the chart of SW2 switch settings you'll notice that the settings for 576K and up are the same as the settings for 64K and up except SW5 is flipped from "1" to "0". As evidenced from this thread apparently the 5150 is happy to keep counting higher; in that thread the user set their card for 96K of additional memory over the 640K mark (IE, they set the switches the same as the 224KB setting except they reversed SW5) and the BIOS will indeed do it. And then the rest of that thread is an argument about whether what they did is "safe" or not because technically the hardware they did this with creates a hardware conflict between the RAM card they added (a clone of the lo-tech) and CGA's built-in video memory. (Optimistically it probably won't physically burn anything up, but it technically wrong and *may* possibly break some CGA software that leverages a hardware oddity that makes the same CGA RAM accessible from two different address ranges.)

Anyway, I recommend you don't do what that poster did with the hardware, IE, enable the "B" page on the Lo-tech for two reasons, A: it is a conflict with CGA, whether it burns up your machine or not, and B: it won't work with Hercules at all... but there is no problem at all with enabling the A page. Again, going by the pattern that seems to be in play here to try this:

A: Set SW2:3 on the Lo-Tech to "on"
B: Set the first five positions of motherboard switch SW2 to "on - on - off - on - off"

Supposedly if this works you'll get 704K recognized without any additional drivers. See what happens, I guess.

Will this trick work on a 5160 board as well?

 

[VERAULT]

Basically I am wondering if this trick can be used on a 5160 or 5155. I am guessing no as it doesnt have the granularity in the switches like a 5150 motherboard has.