Choosing which XTIDE card to buy?

[Anonymoose]

Heyo, I’m looking to replace the hard drive with a more modern Compact Flash option (maybe even sd?), but what should I be looking for? I see many options (like different versions of the XTIDE) and don’t know what I should get.

Another thing, how would I add 640K ram to this computer? Is it as easy as swapping out chips or would I need something else?

 

[Anonymoose]

Heyo, I’m looking to replace the hard drive with a more modern Compact Flash option (maybe even sd?), but what should I be looking for? I see many options (like different versions of the XTIDE) and don’t know what I should get.

Another thing, how would I add 640K ram to this computer? Is it as easy as swapping out chips or would I need something else?

I forgot to add! The computer is a Compaq Portable.

 

[ajacocks]

Welcome to the forum @Anonymoose .

As far as which XT-IDE card to buy, you can’t really go wrong with the original:

Glitch Works XT-IDE rev 4B by Glitch Works, LLC on Tindie

Glitch Works XT-IDE rev 4B XTIDE 8 Bit ISA IDE Interface

www.tindie.com

And it’s fairly easy to upgrade to 640k, even on the system board. You can use a module like this:

Compaq Portable 640K U35 RAM Decoder PROM

SPLD-based replacement of the Compaq Portable RAM decoder PROM (U35). The adapter PCB is arranged so the first slot isn't blocked due to the height of the socket+IC. Allows 640K RAM (64+64+256+256) on the system board. With jumper for stock 256K mode (64+64+64+64). Check the third picture to...

monotech.fwscart.com

Once you have that installed, you can buy the correct DIP DRAM chips and place them on the motherboard.

Good luck!
- Alex

 

[modem7]

Another thing, how would I add 640K ram to this computer? Is it as easy as swapping out chips or would I need something else?

I forgot to add! The computer is a Compaq Portable.

You can use a module like this:

In effect, the module replaces the chip in socket U35, with a version that supports 640K on the motherboard.

Per the information at [here]:
- Some machines already have the 640K version of U35 installed. (Compaq part number 101257-001)
- Revision C of the motherboard BIOS is needed for 640K.

I see many options (like different versions of the XTIDE)

The XT-IDE (and XT-CF) cards have a 'BIOS expansion ROM' on them. The early Compaq Portable's have revision B of the motherboard BIOS, and that BIOS does not support BIOS expansion ROM's. And so to use an XT-IDE (or XT-CF) card, if your motherboard BIOS is not already at revision C, then you would need to upgrade to revision C.

For more information about revision B and revision C of the motherboard BIOS, see the 'Portable and Portable Plus - BIOS revisions' link at [here].

 

[Anonymoose]

Which according to this would be 2 256k chips?

https://minuszerodegrees.net/manuals/Compaq/Compaq%20Portable_Plus_286%20-%20Maintenance%20and%20Service%20Guide.pdf

And is there an XT-IDE card with access from the outside?

Welcome to the forum @Anonymoose .

As far as which XT-IDE card to buy, you can’t really go wrong with the original:

Glitch Works XT-IDE rev 4B by Glitch Works, LLC on Tindie

Glitch Works XT-IDE rev 4B XTIDE 8 Bit ISA IDE Interface

www.tindie.com

And it’s fairly easy to upgrade to 640k, even on the system board. You can use a module like this:

Compaq Portable 640K U35 RAM Decoder PROM

SPLD-based replacement of the Compaq Portable RAM decoder PROM (U35). The adapter PCB is arranged so the first slot isn't blocked due to the height of the socket+IC. Allows 640K RAM (64+64+256+256) on the system board. With jumper for stock 256K mode (64+64+64+64). Check the third picture to...

monotech.fwscart.com

Once you have that installed, you can buy the correct DIP DRAM chips and place them on the motherboard.

Good luck!
- Ale

 

[modem7]

And is there an XT-IDE card with access from the outside?

I presume that question is in reference to the insertion/removal of a CF card.
- One way is per the combination shown in the photo at [here].
- If you look at the variations of XT-IDE and XT-CF cards shown at [here], some of the XT-CF allow CF card insertion/removal via the rear of the computer. (Note: Not hot-swappable.)

 

[modem7]

Which according to this would be 2 256k chips?
https://minuszerodegrees.net/manuals/Compaq/Compaq Portable_Plus_286 - Maintenance and Service Guide.pdf

Careful using that manual, because it covers multiple models (e.g. includes Compaq Portable 286, something different to the Compaq Portable).

Per the motherboard photo at [here], the Compaq Portable has four banks of nine RAM chips. In the manual that you pointed to, PDF pages 115 and 116 show bank identification, and the fact that the 256K sized chips go into banks 2 and 3.

64KB + 64KB + 256KB + 256 KB = 640 KB.

 

[modem7]

The 256K chips are described by Compaq as "256K x 1 RAM", meaning 262,144 (i.e. 256K) uniquely addressable bits. Eight are required to create a bank of 256K bytes. The ninth chip is used to store parity information.

Examples of these chips are in the 41256 link at [here]. I cannot see a RAM chip speed rating in the manual. Use the same speed, or faster (lower 'ns'), than the RAM chips already fitted. Faster chips will not result in better performance. Online photos of the motherboard may assist you.

 

[Anonymoose]

The 256K chips are described by Compaq as "256K x 1 RAM", meaning 262,144 (i.e. 256K) uniquely addressable bits. Eight are required to create a bank of 256K bytes. The ninth chip is used to store parity information.

Examples of these chips are in the 41256 link at [here]. I cannot see a RAM chip speed rating in the manual. Use the same speed, or faster (lower 'ns'), than the RAM chips already fitted. Faster chips will not result in better performance. Online photos of the motherboard may assist you.

Ah, so I’ll need 16 of them? or 18

 

[modem7]

Ah, so I’ll need 16 of them? or 18

From what I read in the manual, the parity chips are mandatory. So, 18.