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8-bit ISA 1MB RAM Board

Hi, yes nearly there with both :) I hope to have both available in the next few days.
 
r02 RAM board design is done at long last - there just aren't enough hours in the day. Design pack here. EMS board is also nearly ready.

As ever, any and all feedback very welcome :)
 
In case anyone is interested, I tested the RAM & EMS boards with Windows 3.0 in a PC/XT and all seems well. Windows sees the EMS and I was able to load and switch between applications without even the hint of any stability issues... though with a 4.77MHz 8088 things did start to get pretty slow with lots open!
 
Good news on the EMS front :) You might want to run Quarterdeck Manifest (MFT.EXE) and choose Expanded -> Benchmark to see if there are any strange bottlenecks anywhere. My 5160 with an Intel Aboveboard shows this (not a clean boot):

Code: 
Expanded / Benchmark
                               (times in microseconds)
         EMS Function        Minimum  Maximum  Average
    Timer Interrupt Latency       0     4096      368


    Map Single Page             578      629      605
    Real Alternate Map Set


    Save All -  4 pages         842      848      846
    Map Multiple -  4 pages    2505     2511     2507
    Restore All -  4 pages     1797     1801     1799


    Save Page Frame             719      726      724
    Restore Page Frame          730      732      732


    Open Handle - 4 pages      1247     1253     1249
    Close Handle - 4 pages     3557     3571     3567
    Open Handle - 31 pages     3090     3099     3097
    Close Handle - 31 pages    4383     4397     4392
 
Thanks for posting that - I've never seen that utility before. And it seems like the original author of the driver I'm working with did a good job - 5155, stock Intel 8088, DOS 6.22:

Code: 
Expanded / Benchmark
                               (times in microseconds)
         EMS Function        Minimum  Maximum  Average
    Timer Interrupt Latency       0     1419       76

    Map Single Page             313      318      315
    Real Alternate Map Set

    Save All -  4 pages         314      318      315
    Map Multiple -  4 pages    1694     1701     1700
    Restore All -  4 pages      848      857      852

    Save Page Frame             427      431      431
    Restore Page Frame          574      578      574

    Open Handle - 4 pages       563      572      570
    Close Handle - 4 pages      751      762      757
    Open Handle - 31 pages     1381     1388     1385
    Close Handle - 31 pages    1581     1587     1584
 
pearce_jj said:
r02 RAM board design is done at long last - there just aren't enough hours in the day. Design pack here. EMS board is also nearly ready.

As ever, any and all feedback very welcome :)
Click to expand...

Hey pearce,

I found that when i tried to submit the gerbers to OSHPark.. it complained there was no 'board outline'.. just an fyi.
 
Ok. I semi asked this earlier, but either i wasn't clear, or i'm just being thick at the moment and am mis-parsing your answer... Since i have 640k right now (well, minus what the tandy steals for video), Do I need _both_ boards, or do I just need the 2 Meg board? (and it'll fill in from the 640k up to the 2 megs).

thanks
 
Hi, the two boards are for different purposes. In your case, the 1MB board could provide some UMB space - how much will depend on the Tandy memory map. Even if there are free physical segments, these may or may not be useful. For example, it can be used by some disk cache and print spoolers, and that's about it.

The 2MB EMS Board provides LIM4 spec EMS, which can be used by any program supporting EMS, including Windows 2 and 3, Lotus 1-2-3 and I presume some games.
 
pearce_jj said:
Hi, the two boards are for different purposes. In your case, the 1MB board could provide some UMB space - how much will depend on the Tandy memory map. Even if there are free physical segments, these may or may not be useful. For example, it can be used by some disk cache and print spoolers, and that's about it.

The 2MB EMS Board provides LIM4 spec EMS, which can be used by any program supporting EMS, including Windows 2 and 3, Lotus 1-2-3 and I presume some games.
Click to expand...

According to the 'technical reference manual' for my SX, "An optional 8 additional 256K RAM chips may be added on the
system board to expand the memory to a full 640K bytes, the maximum RAM allowed by the system memory map."
 
The documentation is referring to the maximum amount of memory addressable by DOS, which is typically capped at 640KB. You can add additional cards to the system that add more memory beyond 640KB, addressed via a variety of means. If your system is already at 640K then jj_pearce's EMS board would make the most sense, since it uses the LIM EMS specification/driver to provide extra memory to programs that can use EMS (disk caches, Lotus 1-2-3, Windows 3.0, Turbo Pascal 6/7, specialized math programs, etc.).
 
One of the biggest things (yeah, i expect a lot, even from hardware I used when i was younger) is to be able to LOADHI to free up as much of that 640K as I can.. Not sure if I would even be able to do that, even with his 'fill in the gaps' card on this machine?

Trixter said:
The documentation is referring to the maximum amount of memory addressable by DOS, which is typically capped at 640KB. You can add additional cards to the system that add more memory beyond 640KB, addressed via a variety of means. If your system is already at 640K then jj_pearce's EMS board would make the most sense, since it uses the LIM EMS specification/driver to provide extra memory to programs that can use EMS (disk caches, Lotus 1-2-3, Windows 3.0, Turbo Pascal 6/7, specialized math programs, etc.).
Click to expand...
 
I could be wrong, but I think both cards should allow you to do that (I use QRAM with my Intel EMS board to load roughly 40K of stuff high) but Pearce's non-EMS board would give you more usable RAM from A000-EFFF to load things high. In theory -- I leave it to him to exactly define each board's capabilities.

In today's retrocomputing landscape, the ability to load things high is not as necessary as it once was. Cutemouse, a very capable mouse driver, fits in roughly 4K. If you need networking, most packet drivers use between 4K-25K and you can use mTCP for just about everything except mounting a remote drive. On an 808x-class system, there's probably not much else you need to load resident. Once you hit a 386 and higher, there are CDROM drivers and MSCDEX and other stuff to worry about, but then you have the benefit of a memory manager that can do it for you.
 
Trixter;321962 In today's retrocomputing landscape said:
Good point.. I already have the packet driver in place for my NE2K card, and have been using mTCP. It's been so long since I had used a machine of this level (Circa 1991-1993), that I got too used to _having_ to have so much conventional memory free. Part of why i've been trying to sort this out also, is because i only have 5 slots.. and if i needed both boards, it gets tight, since the tandy parallel port is being a thorn, so i'm using an additional card for a proper port (for the SD card interface for 'backup storage').
Click to expand...
 
Does the SX have the DOS in ROM like the SL/TL? As I seem to recall that was presented via a windowing mechanism in upper memory.
 
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