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DEC units on ebay

thunter0512 said:
Does anyone know what happened to Ebay seller "JC GLOBAL TECH" also known as "jcrecycling_2020" ?
They used to be very responsive and good to deal with, but have now become unresponsive.
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I went there last fall to pick up a DEC Pro 380. Pretty sure they are in business. I have the owner's phone. PM if you need it.
 
This time in Europe:
EBAY
Teleprinter 390 is a ASR-33 in a different housing. It is a bit more quiet.

I have one of this model and it has the "reader run" you need for the PDP8 speed limitation of Focal etc.. I like this machine very much. It's more heavy than an ASR-33.
 
thunter0512 said:
Does anyone know what happened to Ebay seller "JC GLOBAL TECH" also known as "jcrecycling_2020" ?
They used to be very responsive and good to deal with, but have now become unresponsive.
Click to expand...
I bought a set of boards from them at the end of November, and they responded promptly to my offer. Monday was a US holiday. Maybe they're extending the long weekend?
 
thunter0512 said:
Does anyone know what happened to Ebay seller "JC GLOBAL TECH" also known as "jcrecycling_2020" ?
They used to be very responsive and good to deal with, but have now become unresponsive.
Click to expand...
I've bought a number of things, but nothing recently. I've sent a couple of seller messages inquiring about various things but never received a reply about that. I did send seller messages in regard to items I'd purchased and did get replies to those.
 
Sorry if this is a duplicate post, but I didn't see any other:

DEC PDP 8L Very Rare but Most Popular in late 1960s

www.ebay.com

DEC PDP 8L Very Rare but Most Popular in late 1960s | eBay

<p dir="ltr" style="margin-top:0; margin-bottom:0;">DEC finally addressed non-industrial mini computer that private people can buy, but it was still too expensive to the average computer loving hobbyist. It was introduced late in the 1960s that acted much like THE expensive and complex PDP...
www.ebay.com

smp
 
czunit said:
Neat. How is the performance with and without it?
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Obviously will be slower without the cache, but performance will be highly dependent on the memory access workload.
I haven't really run it without the cache, except for testing. It does run fine without the cache module present, passes CPU diagnostics (except cache of course), boots and runs XXDP, RT11, etc.
Basic console operations from XXDP like doing DIR of a device and loading running diagnostics does not seem much different (as probably would be expected).
 
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Ok. I've always wondered what kind of performance improvement memory cache did in the era of MOS memory. Back with core it was a massive difference but I've wondered about MOS.
 
czunit said:
Ok. I've always wondered what kind of performance improvement memory cache did in the era of MOS memory. Back with core it was a massive difference but I've wondered about MOS.
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The 1MB MOS memory in the 11/44 MS11-P has a read access time of 500ns or so. Core memory was usually about twice that in the 1000ns range.
I am not aware of core being a supported option on the 11/44. It is on the 11/04-34 systems in the BA11K box with the configurable regulators.

With the cache, the memory access time goes down to data arriving at the end of the current CPU microcycle, so basically a 0ns additional delay.
The cache helps when the data in the cache is used more than once, so instruction loops, or data that is read/written multiple times in a loop get the benefit.

Some caches, like the 11/70 in particular, also benefited from prefetch, as it had a 32b path to memory so any cache fill on the PDP-11/70 would prefetch (usually)
the next word, so processing instructions or data sequentially benefitted significantly.

The 11/34 and 11/44 caches have only a 16b wide access to memory (ie, the UNIBUS) so there is no inherent prefetch by these caches. So no help there.
The caches only help when a given memory word is used more than once before it is replaced in the cache.
 
*nod* Good info. The pdp11/73 and 83 boards (Quad) can also do a 32 bit fetch from PMI memory, that's what seems to make PMI worth it. The 11 loads the first word into memory, lets the CPU get rolling, then at the end of the cycle "steals" the next word from memory and stuffs it in cache. Kind of cool.

The cache must have really helped because the 11/44 had a lot of logic for cache snooping and invalidation for a multi-CPU 11/44 system. Which was never built, but I recall it was in there (unlike the 11/34 and 11/60 caches).

Fun stuff, might be worth benchmarking if I ever get an 11/44. Meantime I have to get back to fixing these pdt11/150's.
 
AK6DN said:
Missing the cache module of the cpu complex, and no RX211 interface board either. One 1MB ECC memory board (if fully populated). Listed as untested. $4900 is totally unrealistic. Maybe $1000....
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The seller is that JC Global Tech recycler. He will take a reasonable best offer, though I don't know if he'd go as low as $1000.
 
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