Building a new memory expansion for my Compaq Portable 3!

[@PixelPipes]

I'll be honest, I just use the built in HIMEM.SYS driver in DOS 6.22 and it seems to work fine for the expanded memory on my machine. I don't have the newer revision with the chip.

[@silvestronsbitsandbytes]

Must be something to do with the version of DOS then, as I'm sticking with 3.31 that was provided by Compaq at the time of this machine. Lots more experimentation needed!

[@danielflakelar8193]

Dammm Dude, You could have said you were doing this. I would have definatly done 2 of them

[@leecremeans5446]

Unless you're running software that expects it (mostly things like 1-2-3 itself and a few demos), you don''t need to have EMS enabled. You can use XMS and load DOS high if you have MS-DOS 5.0 or higher and HIMEM.SYS loaded.

[@silvestronsbitsandbytes]

I'm trying to stick to the Compaq OEM DOS 3.31 that would have been available for this machine, which doesn't have himem etc. Good to know about programs that really need it. Might need to find something just so I have an excuse to test it out. Still really curious what CEMMP is used for!

[@williefleete]

If you have or thinking of getting a compaq SLT 286 I’ve been slowly reverse engineering the memory and modem slot, etc. I have made an adapter for using standard floppy drive(s) on the 26 pin floppy connector and a mostly working serial port card, needs some work but sends and receives ok, haven’t worked on making the RAM cards for it yet but have design files for them, the computer uses “pseudo SRAM” as does the ram cards instead of DRAM, I figure modern SRAM would work in them though

[@silvestronsbitsandbytes]

SLT 286 is definitely on my want list! Would love to hear more when you're ready to release

[@williefleete]

@@silvestronsbitsandbytes some things to know if you do get one. The RTC block will need replacing as the cell in it will be exhausted and it needs to work to hold config and boot, the original power brick does have 4 low value Rifa caps (from line/neutral to earth may trip RCDs/gfci if they leak). By default the floppy drive will only boot DD but it is a HD drive. I think hard drive choices are limited, I’ve found some drives don’t allow the machine to even POST, 64MB CF card works and a 64MB IDE flash drive from a thin client worked but a 128MB CF card didn’t yet a 1gig worked (with 500 meg limit) and it seems picky even with mechanical drives

[@silvestronsbitsandbytes]

Pretty much all identical things to the CP3, other than the lack of RIFAs.

[@MrLurchsThings]

I’ve been searching for years for the same thing for my Compaq Portable II. No joy 😢

[@silvestronsbitsandbytes]

Could the Portable II take a lo-tech memory expansion ISA card? 🤔

[@pipschannel1222]

@@silvestronsbitsandbytes It would fit of course but those cards are 8-bit memorycards that are meant for XT class machines and to be used as expanded memory. What would work is a 16-bit Intel Aboveboard. My Portable II had the proprietary Compaq expansion board, but I sold that machine two weeks ago.. Currently working on a III as well 🙂 On the II the ISA bus runs at the same speed as the CPU so in theory there won't be a performance difference between an original Compaq board and an aftermarket cards like the Intel unit..

[@silvestronsbitsandbytes]

@@pipschannel1222 interesting, thanks for that! I'd only seen the lo-tech boards, not ever really looked closely. I have some work to do on my II as well, maybe this will join the queue 😃

[@zbradbell]

@@silvestronsbitsandbytes I just started a thread on VCFed about trying to recreate the memory board that goes underneath the Portable II motherboard. Could definitely use the help if you wanted to collab!

[@silvestronsbitsandbytes]

That's awesome @zbradbell! Sorry for the delay, YT doesn't surface these comments very well :( I'm all in! Let's do THIS!