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lutiana
June 23rd, 2017, 07:49 AM
Okay, I have a few:

1. Will the IBM 5150 and 5160 work with the 28C256 chips? If not, what type of EEPROMS are best?
Answer:


The 5160 can use the 27C256 chips, which are *almost* identical to the 28C256 chips. Pin 1 on the chip needs to go to pin 27 on the socket and pin 27 on the chip can be bridged to pin 28 (to disable write enabling).
The 5150 can use the 28C256, but there will be 4 pins not in the socket (1,2, 27 and 28 ), you then need to lift pin 26 and run pin 27 on the chip to pin 24 on the socket and bridge pin 27 on the chip to pin 27 on the chip (that runs to pin 24 on the socket). You then need to tie pins 1,2,26 and 28 to pin 27 (to tie them high).


2. I have a 5150 motherboard that has some minor corrosion around the crystal. So I am wanting to replace it. What specs should I be looking for? Answer: 14.31818 MHz

3. Where can I get a replacement connector for AT power input on a motherboard? What is that connector called? Answer: It is a Molex 15-48-0106, which is obsolete but you can get a Molex 36642-0001, which is the replacement.

4. What is the best way to clean minor corrosion from a 5150 motherboard? I don't think any traces are damaged, it seems like it is surface corrosion only.

5. Someone mentioned you can hack a 5160 motherboard so that it will have 640kb of memory on board, can the same be done for a 5150? I cannot find the link that someone posted about this, so if you have it can you post it? Answer: It is theoretically possible, but not easy at all.

Stone
June 23rd, 2017, 08:19 AM
5. Someone mentioned you can hack a 5160 motherboard so that it will have 640kb of memory on board, can the same be done for a 5150? I cannot find the link that someone posted about this, so if you have it can you post it?I think it only works for XTs.

http://www.textfiles.com/computers/xt-640k.upd

ibmapc
June 23rd, 2017, 09:04 AM
Okay, I have a few:

1. Will the IBM 5150 and 5160 work with the 28C256 chips? If not, what type of EEPROMS are best?

I use 29C256 EEPROMs on my 5155(same motherboard as early 5160). I went that route because they are closer to being pin compatible to the original EPROM. Only one mod necessary to prevent incidental writing to the chip




5. Someone mentioned you can hack a 5160 motherboard so that it will have 640kb of memory on board, can the same be done for a 5150? I cannot find the link that someone posted about this, so if you have it can you post it?
With just a little more effort you can put 1 MB on the 5160 and have UMB memory for mouse drivers and network drivers and such. I'm not sure about the 5150. I could have sworn I saw a mod mentioned somewhere to put 640k on the 5150 motherboard but I can't find it now.

Stone
June 23rd, 2017, 09:22 AM
With just a little more effort you can put 1 MB on the 5160 and have UMB memory for mouse drivers and network drivers and such.
http://www.vcfed.org/forum/showthread.php?15282-Upgrading-an-IBM-XT-to-640k&p=270500#post270500

Scali
June 23rd, 2017, 11:11 AM
Here is a document describing it for the 5160: http://www.minuszerodegrees.net/5160/motherboard/5160_upgrading_256k_motherboard_to_640k.pdf
It describes modifying a 'type 1' (64k-256k) XT motherboard to a 'type 2' motherboard (640k).
I suppose in theory you could make it work for the 5150 as well, but the question would be: how much modification would have to be done?
I believe there are also two types of 5150 motherboard: 16-64k and 64k-256k, see here:
http://www.minuszerodegrees.net/5150/motherboard/5150_motherboard_revisions.htm
The latter should not be too different from a 'type 1' XT motherboard, so by that logic, it should be doable to perform the 640k mod on it as well.
It uses 4 banks of 4164 memory chips, just like a 'type 1' XT does.

The older motherboard uses 4 banks of 4116 memory. It will be harder to modify that one, but perhaps not impossible either.

The circuit diagrams for all boards are available in the respective manuals, so someone with enough knowledge of these early memory chips should be able to figure out what the relevant changes were between the different models, and figure out how to do it.

Apparently someone did it to fatwizard's 5150 256k board in the post that Stone linked above. I can only say... it doesn't look easy :)

lutiana
June 23rd, 2017, 11:26 AM
http://www.vcfed.org/forum/showthread.php?15282-Upgrading-an-IBM-XT-to-640k&p=270500#post270500

Holy hell that does not look like something I am up for. I'll leave all my 5150s at the 256Kb that they have (they are all 64-256kb motherboards).

ibmapc
June 23rd, 2017, 11:57 AM
http://www.vcfed.org/forum/showthread.php?15282-Upgrading-an-IBM-XT-to-640k&p=270500#post270500

That shows both topics (5150 640k mod and 1 MEG XT mod) on one page. Great find Stone. A direct link to the tread about the 1 MEG XT Mod is HERE. (http://www.vcfed.org/forum/showthread.php?28128-HIMEMV2-or-equivillent-PROM)

PS
I am still willing to supply the GAL to do the 1 MEG XT mod for the cost of shipping.

lutiana
June 23rd, 2017, 12:01 PM
I use 29C256 EEPROMs on my 5155(same motherboard as early 5160). I went that route because they are closer to being pin compatible to the original EPROM. Only one mod necessary to prevent incidental writing to the chip

The 28C256 work well on the 5170 motherboard, and they are what I have. So i am really hoping that they would work in the 5150 and 5160.




With just a little more effort you can put 1 MB on the 5160 and have UMB memory for mouse drivers and network drivers and such. I'm not sure about the 5150. I could have sworn I saw a mod mentioned somewhere to put 640k on the 5150 motherboard but I can't find it now.

The 512-640 upgrade for the 5160 is VERY easy from what I read. So how do you do 640-1024? I read the post that Stone posted and it seemed like there was quite a bit of fiddling with code and PROMS to do this. Is there a step by step guides somewhere?

Malc
June 23rd, 2017, 12:01 PM
I've not seen that before, It looks like a lot of work, I have a sixpakplus card in my 5150 which takes it to 640k, It also benefits from having a clock / serial and parallel port.

lutiana
June 23rd, 2017, 12:05 PM
That shows both topics (5150 640k mod and 1 MEG XT mod) on one page. Great find Stone. A direct link to the tread about the 1 MEG XT Mod is HERE. (http://www.vcfed.org/forum/showthread.php?28128-HIMEMV2-or-equivillent-PROM)

PS
I am still willing to supply the GAL to do the 1 MEG XT mod for the cost of shipping.

So the mod is simply replacing the BIOS with the GAL and putting in 256k chips in all the banks? I tried to follow the thread, but got lost (probably doesn't help that I have about 10 things going in at once here).

ibmapc
June 23rd, 2017, 12:17 PM
So the mod is simply replacing the BIOS with the GAL and putting in 256k chips in all the banks? I tried to follow the thread, but got lost (probably doesn't help that I have about 10 things going in at once here).

Yes, that is a long thread. It's the PAL at u44 that gets replaced by the GAL(not BIOS) and then it's just a matter of putting USE!UMBS.SYS on your hard disk and modifying config.sys and autoexec.bat. I'll type up some instructions to make it easier to follow but it's really not very difficult.

per
June 23rd, 2017, 12:23 PM
One of the biggest changes from the 5150 to the 5160 motherboard is that the 5160 has a way more flexible memory layout. While the 5150 is hardwiered for one spesific type of RAM, the 5160 allows for a wide variety of different RAM-type combinations. By default it has presets for 4 different scenarios:

* all 4164 (default, 64K steps up to 256K)
* a combination of 4164 and 41256 (later default, needs a multiplexer in the empty socket, 640K max)
* all 4216 (64K only, needs some additional jumper modifications)
* all 41128 "piggybacked" dram (needs multiplexer, 128K steps up to 512K)

Everything is controller by a small ROM chip decoder that mannages the select lines to the different banks. The 1MEG mod replaces this ROM with one that also enables RAM in upper memory.

lutiana
June 23rd, 2017, 12:27 PM
Yes, that is a long thread. It's the PAL at u44 that gets replaced by the GAL(not BIOS) and then it's just a matter of putting USE!UMBS.SYS on your hard disk and modifying config.sys and autoexec.bat. I'll type up some instructions to make it easier to follow but it's really not very difficult.

I'd like to get one or two of the GALs from you then for my 5160s and give it a go. I know that one of them has a 256-640 motherboard, but I am not sure about the other one (though I am thinking it is the first revision mb). Having 1Mb on each of them would be quite useful.

lutiana
June 23rd, 2017, 12:29 PM
One of the biggest changes from the 5150 to the 5160 motherboard is that the 5160 has a way more flexible memory layout. While the 5150 is hardwired for one specific type of RAM, the 5160 allows for a wide variety of different RAM-type combinations.

Yes, I am realizing that upgrading the memory past 256Kb on the 5150s I have is not really going to be all that feasible. So I'll just look to add in ISA cards to fill out the memory on them.

ibmapc
June 23rd, 2017, 12:42 PM
...I know that one of them has a 256-640 motherboard, but I am not sure about the other one (though I am thinking it is the first revision mb). Having 1Mb on each of them would be quite useful.
The 256-640k motherboard may be a little more difficult. The ones that I've seen have the PROM at u44 soldered directly where as the 64-256k boards use a socket for u44. You would have to de-solder the chip on the 256-640k board (and solder a socket of coarse). None the less, I'd be happy to supply the GAL(s) and some basic instructions. I could even put the latest version of USE!UMBS.SYS on a 360k floppy if you like. Just send me a PM with your address, and I'll get it going.

lutiana
June 23rd, 2017, 12:48 PM
The 256-640k motherboard may be a little more difficult. The ones that I've seen have the PROM at u44 soldered directly where as the 64-256k boards use a socket for u44. You would have to de-solder the chip on the 256-640k board (and solder a socket of coarse). None the less, I'd be happy to supply the GAL(s) and some basic instructions. I could even put the latest version of USE!UMBS.SYS on a 360k floppy if you like. Just send me a PM with your address, and I'll get it going.

That would be awesome. I'll have to take a look at the 5160 I have at home later tonight and see if U44 is soldered on or not. I don't really have an issue unsoldering and replacing it with a socket if i have to.

Stone
June 23rd, 2017, 01:23 PM
The 512-640 upgrade for the 5160 is VERY easy from what I read.You need to read it again. It's a 256 - 640 upgrade and it takes all of 5 minutes to perform. :-)

lutiana
June 23rd, 2017, 04:12 PM
So I still need the answers to these:

2. I have a 5150 motherboard that has some minor corrosion around the crystal. So I am wanting to replace it. What specs should I be looking for?

3. Where can I get a replacement connector for AT power input on a motherboard? What is that connector called?

4. What is the best way to clean minor corrosion from a 5150 motherboard? I don't think any traces are damaged, it seems like it is surface corrosion only.

And maybe an idea of what chip type to use for an IBM 5150s bios.

per
June 23rd, 2017, 04:28 PM
2. Look for 14.31818 MHz. It can be trimmed a bit with the variable capacitor, but CGA composite will only display proper colors if it's tuned spot on.

For the BIOS, the chip you want to look for is the 2364.

lutiana
June 23rd, 2017, 05:01 PM
2. Look for 14.31818 MHz. It can be trimmed a bit with the variable capacitor, but CGA composite will only display proper colors if it's tuned spot on.

There is a an adjustable thingy on the motherboard, which I assumed was for just this purpose based on reading things about the 5150. Would the variable capacitor be in addition to this?

per
June 23rd, 2017, 06:16 PM
There is a an adjustable thingy on the motherboard, which I assumed was for just this purpose based on reading things about the 5150. Would the variable capacitor be in addition to this?
That thingy IS the variable capacitor. It just ajusts the frequency a little bit upwards or downwards.

modem7
June 23rd, 2017, 07:26 PM
And maybe an idea of what chip type to use for an IBM 5150s bios.

For the BIOS, the chip you want to look for is the 2364.
1. Goto minuszerodegrees.net (http://minuszerodegrees.net)
2. Navigate to 5150 area
3. Choose: Substituting the U33 BIOS ROM

modem7
June 23rd, 2017, 07:29 PM
There is a an adjustable thingy on the motherboard, which I assumed was for just this purpose based on reading things about the 5150. Would the variable capacitor be in addition to this?

That thingy IS the variable capacitor. It just ajusts the frequency a little bit upwards or downwards.
1. Goto minuszerodegrees.net (http://minuszerodegrees.net)
2. Navigate to 5150 area
3. Choose: Motherboard Switch/Jumper Settings
4. Scroll to bottom of page to view 'Trimmer T1' section

Chuck(G)
June 23rd, 2017, 07:44 PM
It should also be noted that a Motorola 68765 UV EPROM will also work in the BIOS socket. Of course, the same problem obtains in finding a programmer for this. Fortunately, I have such and have used the '765 in a 5150 quite successfully.

modem7
June 23rd, 2017, 07:49 PM
It should also be noted that a Motorola 68765 UV EPROM will also work in the BIOS socket. Of course, the same problem obtains in finding a programmer for this. Fortunately, I have such and have used the '765 in a 5150 quite successfully.
Thanks. On my web page, I will add the 68765 to the existing 68766 info.

ibmapc
June 26th, 2017, 12:46 PM
Okay, I have a few:

1. Will the IBM 5150 and 5160 work with the 28C256 chips? If not, what type of EEPROMS are best?
Answer:

[LIST]
The 5160 can use the 27C256 chips, which are *almost* identical to the 28C256 chips. Pin 1 on the chip needs to go to pin 27 on the socket and pin 27 on the chip can be bridged to pin 28 (to disable write enabling).
....
The 29C256 is a better option. You only need to be concerned with the WE pin(write enable). And I'm not convinced that even that is really needed but I tied it to pin 1 to hold it high anyway on mine(because Chuck(G) said so, and I always do what Chuck say's;) ) . If interested, you can find them HERE (http://www.ebay.com/itm/Atmel-AT29C256-12PC-29C256-256KBIT-CMOS-FLASH-EEPROM-DIP28-x-2pcs/152597992869?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2057872.m2749.l2649). I have bought from this guy twice before and had no issues. In fact, he is quite easy to communicate with. His original listing was for 10 pieces. I told him I only wanted 4 and he created a new listing with reduced quantity.

lutiana
June 26th, 2017, 01:33 PM
The 29C256 is a better option. You only need to be concerned with the WE pin(write enable). And I'm not convinced that even that is really needed but I tied it to pin 1 to hold it high anyway on mine(because Chuck(G) said so, and I always do what Chuck say's;) ) . If interested, you can find them HERE (http://www.ebay.com/itm/Atmel-AT29C256-12PC-29C256-256KBIT-CMOS-FLASH-EEPROM-DIP28-x-2pcs/152597992869?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2057872.m2749.l2649). I have bought from this guy twice before and had no issues. In fact, he is quite easy to communicate with. His original listing was for 10 pieces. I told him I only wanted 4 and he created a new listing with reduced quantity.

Yes, looking at the pin outs the 29C256 is a much better choice, but I have the 28C256 chips, and a way to program them (which won't work on 27x or 29x chips). So I am going to just deal with the small mods to make them work in the socket.

ibmapc
June 29th, 2017, 11:03 PM
@lutiana
I'm attaching files here with drivers and instructions for the 1megXT mod. 39404

lutiana
June 30th, 2017, 05:05 PM
@lutiana
I'm attaching files here with drivers and instructions for the 1megXT mod. 39404

Awesome! Thanks.

Quick question, it looks like it uses D000h-F000h, but won't that interfere with the XT-IDE?

ibmapc
June 30th, 2017, 05:50 PM
Awesome! Thanks.

Quick question, it looks like it uses D000h-F000h, but won't that interfere with the XT-IDE?
You should be able to put XT-IDE at C800. That's where mine is at.

ibmapc
July 15th, 2017, 08:49 PM
You should be able to put XT-IDE at C800. That's where mine is at.

@ Lutiana, Any updates on this project?