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PC-DOS 3.2 for 5150

maxtherabbit

maxtherabbit

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Thinking about downgrading my 5150 to DOS 3.2 to save a few more kB of conventional. Any reason not to? Looks like all of the changes in 3.3 aren't really relevant to my configuration anyway - am I missing anything? Is there any significant amount of software that would balk at a DOS version sub 3.3?
 
I have come across IBM software that requires PC-DOS 3.3. But if that is something you need, you'd just deal with it.

It's easy to keep a boot disk for 3.0 and 3.3, if you have both anyway; that's what I do.
 
maxtherabbit said:
Thinking about downgrading my 5150 to DOS 3.2 to save a few more kB of conventional. Any reason not to? Looks like all of the changes in 3.3 aren't really relevant to my configuration anyway - am I missing anything? Is there any significant amount of software that would balk at a DOS version sub 3.3?
Click to expand...

What is your full 5150 hardware configuration?
 
256kB system board
Paradise auto switch EGA
Ast 6 pak (640kB fill)
360kB drive A 720kB drive B
ST225 drive C MM212 (10MB) drive D
LTEMS card
WD8003 NIC
V20/8087
 
If you only have a 10Mb drive, run DOS 2.11 and you'll get even more free memory back.

If you really want to maximize free DOS RAM, run DR-DOS 6 and load HIDOS.SYS and you'll get ~612K free, as it can take advantage of your EMS card to create UMBs and load the DRDOS kernel up there.

However, with 640K, *AND* an EMS card, the last thing you need to worry about is a few more K of free DOS RAM. Your 10MB drive won't let you store any software that can actually maximize the full 640K, other than spreadsheets and word processors, so the exercise is somewhat pointless. I wouldn't bother.

640K, EMS, NEC V20, 8087, EGA... but limited to a 10MB drive? Curious why you chose that build.
 
The boot HDD is a ST225 which is 20MB. 10MB is the secondary HDD.

As for the configuration, I didn't exactly just choose it out of the clear blue. I've had this machine for over 20 years and it's been gradually evolving. Only recent changes are the addition of the 720kB floppy and the EMS card.

3.2 is the minimum DOS version to support the DRIVPARM config directive that I use to support the 720kB drive. I'm getting about 585kB free now with DOS 3.2 and my EMM, packet driver, and DRIVER.SYS (for an external floppy) loaded. So I'm satisfied, that's plenty for anything
 
maxtherabbit said:
LTEMS card
Click to expand...

I assume that's the Lo-Tech 2MB EMS card? If it is and you want to test a random thing some joker on the internet came up with I wrote a little point-enabler dingus, "ems2umb.exe" to set up a card compatible with the LTEMMS card to give you 64k of upper memory space without having to load the resident driver. The driver as compiled will only work if the I/O of the card is set to the default 260h.

Anyway, using this lets you use USE!UMB.SYS to do upper memory stuff with MS-DOS 5 or later while saving the ~5k or so the EMS driver takes up. Obviously you don't get to use EMS when using it for this.
 
Yes it's the lo tech. I'm content with the amount of free memory I have now and don't want to sacrifice 2MB of EMS for 64kB of UMB. I saw your tool before and it is cool though
 
maxtherabbit said:
Yes it's the lo tech. I'm content with the amount of free memory I have now and don't want to sacrifice 2MB of EMS for 64kB of UMB.
Click to expand...

Yeah. I'm just curious if it works on anyone else's hardware. The card I built *should* be 100% "register compatible" with the Lo-Tech card and it works with the EMM driver for it, but technically the hardware's completely different so, I dunno, gremlins. ;)
 
Eudimorphodon said:
Anyway, using this lets you use USE!UMB.SYS to do upper memory stuff with MS-DOS 5 or later while saving the ~5k or so the EMS driver takes up. Obviously you don't get to use EMS when using it for this.
Click to expand...

IMO, it's more effect to load the driver and then load QRAM so that QRAM can extend 640K to 736K, assuming the LIM EMS board allows mapping into A000 and beyond (Intel boards don't, I've unfortunately verified). Trading 5K of driver to 91K more space in low DOS RAM, breaking the 640K barrier, is totally worth it.
 
Trixter said:
IMO, it's more effect to load the driver and then load QRAM so that QRAM can extend 640K to 736K, assuming the LIM EMS board allows mapping into A000 and beyond.
Click to expand...

The LTEMS board doesn't have any mapping capability; the driver is "EMS 4.0" compliant but only because under the EMS 4.0 standard basically *any* EMS 3.2-compliant board can be, all the hardware mapping features from EEMS were completely optional. You get the 64k page frame and nothing else.

(Therefore using the driver instead of a static shim doesn't buy you anything. All the shim does is cram the values 0-3 into the paging registers to make sure each points to a unique 16k page of RAM instead of potentially pointing at the same page or empty space. The latter is possible because the paging system allows more pages of memory than are actually implemented.

Certainly things would be different with a "real" EMS 4.0/EEMS board.)
 
Yep. I built the lo tech on a lark just to play with it but it is pretty limited compared to a rampage or bocaram or above board. However it is *very* fast. Being limited to only a 64kB page frame (that is also 64kB aligned) is kind of lame
 
maxtherabbit said:
Yep. I built the lo tech on a lark just to play with it but it is pretty limited compared to a rampage or bocaram or above board. However it is *very* fast. Being limited to only a 64kB page frame (that is also 64kB aligned) is kind of lame
Click to expand...

I built it into my ridiculous Tandy 1000 expander mostly because I had logic to spare in the GALs and wanted to soak it up with something. It’s primarily good for shock value. (“EMS in a 1000 EX?! That’s un-possible!”.)
 
Dammit. I wonder if I can cancel my LTEMS order. I recall bringing this up during development but I must have made assumptions.

I've been trying to extend DOS past 640K on my 5160 and have been thwarted at every turn. All my EMS boards are Intel, and Intel followed IBM's recommendations to the letter and WILL NOT map into A000. I bought a LT memory board and put 64K directly into A000, but all of the tricks (704K.COM, etc.) seem to lock up the system even though they test the RAM as ok. (Meanwhile, on my goofball AT&T 6300 with an EEMS 3.2 board, EMS + QRAM = 736K free DOS RAM effortlessly.)
 
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Trixter said:
I bought a LT memory board and put 64K directly into A000, but all of the tricks (704K.COM, etc.) seem to lock up the system even though they test the RAM as ok.
Click to expand...

That's really weird; I wonder what in the world they're choking on. There's certainly nothing special about the lo-tech RAM card that should cause problems. If the memory wasn't testing OK I'd almost wonder if there's something up with the 5160's internal memory decoding that's causing some weirdness.

(One of the things I did with my Tandy 1000 expansion is I actually made it an option to put the EMS page frame at A000; since the T1000 has CGA-like video there's no conflict and it frees up more of the upper memory to be filled with the 128k of spare RAM it has specifically for UMBs. I haven't found anything that chokes on an EMS page frame at that location, at least. Unfortunately I can't test doing the "704k" thing because of the Catch-22 that a Tandy 1000 effectively creates a 16k (or bigger) memory hole between DOS memory under 640k and the A-page unless you plug in a VGA card... at which point the A-page is needed for other things.

I've sometimes wondered if anyone would be interested in an ISA version of my card, IE, a new "Six Pack" for 256k-or-bigger XTs; doing a 704/736k backfill would be an easy option to add.)

I've kicked around in my head a few times the idea of making a fully EMS 4.0-compatible card that can do actual remapping, maybe using a fast SRAM as the mapping register, but it's a darn complicated standard and I'd have *no prayer* of writing the necessary driver myself. If someone has sufficiently detailed specs to an existing card maybe making a software compatible one would be an outside possibility.
 
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If you were going to go the distance with a new 6 pak of sorts, allowing it to backfill conventional from 256kB up AND provide EMS while being able to page flip them over the whole range like a LIM 4.0 card would be bad ass
 
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