[Simh] Any chance of AXP for SIMH ?

[Ray Jewhurst]

I am also looking for an Alpha simulator. Problem with FreeAXP is that it
won't run in Wine and I only have Linux. There used to be one called
AlphaVM Free but now they charge a prohibitive cost for the hobbyist
version.

On Nov 20, 2017 11:45 AM, "Eberhard Heuser" <
eberhard.heuser at chemie.uni-konstanz.de> wrote:

> Am 20.11.2017 um 17:36 schrieb Hittner, David T [US] (MS):
>
>> I'm actually working on the Alpha implementation right now, during my
>> not-as-free-as-I-would-like time.
>>
>> Why is it taking so long?
>> -------------------------------
>> The Alpha is amazingly complex, as you have to simulate the entire set of
>> PC devices (JDEC memory, RT Clock, APICs, Serial Ports, etc.) and buses
>> (PCI, ISA, EISA, SCSI, USB, etc.) that have not been developed for SIMH
>> yet. I have recently found almost all of the needed PC device simulation
>> logic in the QEMU code base, and might be able to port that logic into the
>> SIMH simulator to speed up the development process. Driving the SCSI bus
>> state transitions will be particularly time consuming without the real
>> dedicated SCSI processors which were on every SCSI device and host card.
>>
>> I have the Alpha simulator booting and running some 68 million
>> instructions before it gives up due to a "fatal hardware error", but it
>> hasn't gotten up to the firmware chevrons (>>>) yet, as I haven't simulated
>> most of the required hardware devices yet. The Alpha Firmware itself is a
>> very complex OS, initializing and testing the hardware, and setting up all
>> of the in-memory data structure required by the Alpha Architecture manual,
>> before running the interactive console chevron dialog.
>>
>> What about JIT?
>> --------------------
>> The emulator is also amazingly slow compared to real hardware due to the
>> sheer number of emulated instructions executed and the emulation overhead.
>> JIT would be a wonderful thing, but it's more important to get the
>> emulation right than to make it work faster, as (theoretically) newer host
>> hardware will eventually "catch up" to the emulation overhead. That said,
>> the TCG (Tiny Code Generator) component of QEMU has made me think that we
>> could "do some JIT" in SIMH, either at the single instruction level or at
>> the block level. The primary impact of adding JIT to the emulator is that
>> it throws the emulated clock off - SIMH time, IO, and polling works by
>> counting emulated instructions, and if the emulation instruction count
>> "jumps"  because you executed a large block of JIT code, it could
>> significantly delay or miss the response required for SIMH polling and
>> simulated clock interrupts. It is unlikely that a SIMH Alpha emulation will
>> ever hit the speeds of the commercial emulators, since SIMH is designed be
>> portable, and the commercial emulators are tweaked for specific host
>> platforms. Note that SIMH VAX has never hit the speeds posted by commercial
>> VAX emulators, but runs on almost anything. It is probable that JIT would
>> only be possible on specific host processors or host OS's, requiring that
>> the emulator be capable of both JIT and non-JIT operation.
>>
>>
>> If anyone would care to help in the Alpha development process, I can
>> start checking my code in to allow other developers to assist. If you are
>> interested in helping, send me an email.
>>
>> In the meantime, if you just want to run a free Alpha emulator, the
>> FreeAXP emulator from MSI is and will continue to be available.
>>
>> David Hittner
>>
>> -----Original Message-----
>> From: Simh [mailto:simh-bounces at trailing-edge.com] On Behalf Of Paul
>> Koning
>> Sent: Monday, November 20, 2017 8:58 AM
>> To: Gordon Miller <gordonamiller60 at gmail.com>
>> Cc: simh at trailing-edge.com
>> Subject: EXT :Re: [Simh] Any chance of AXP for SIMH ?
>>
>>
>>
>> On Nov 20, 2017, at 12:07 AM, Gordon Miller <gordonamiller60 at gmail.com>
>>> wrote:
>>>
>>> Hi guys
>>>
>>> I'm the new kid here, despite my grey hair.
>>>
>>> Anyway, what I'm quite interested in, is any kind of Alpha AXP support
>>> for SIMH.
>>>
>> Take a look at the current code, there is an "alpha" subdirectory.  I
>> don't remember the status of that, probably quite preliminary but there are
>> at least some pieces in place.
>>
>>         paul
>>
>>
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>
> Take a look into the es40 source code:
>
> https://sourceforge.net/projects/es40
>
> eberhard
>
>
>
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